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Trade of Motor Mechanic Module 3

1. Some vehicles have transmission cooler lines attached to the radiator Remember to disconnect these lines when removing the radiator and always refit before refilling the system with coolant Refill the system with the correct coolant at the proper anti freeze water ratio There are a number of different types of coolant often recognized by colour as they have different chemical additives that can affect the materials that the engine and system components are made from It is advisable to pressure test the system to check for leaks on completion of the job Start the engine warm it up until the thermostat has opened and check for proper operation of the cabin heater Check for proper coolant level after it cools sufficiently Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 Module 3 Unit 3 Cooling System Step by Step Instruction iv Drain the coolant Place a drain pan below the radiator and remove the drain plug Drain the coolant from the system Replace the drain plug and dispose of the drained coolant in an environmentally approved manner Remove the radiator Carefully remove any hoses that are attached to the radiator Unscrew any cowlings or covers from the radiator Remove the bolts or screws that hold the radiator in position in the engine bay and lift the radiator from its location Inspect the radiator Carry out a visual inspection of the radiator to ensure that it is suitab
2. Phase Trade of Motor Mechanic Module 3 Unit 3 COOLING SYSTEM Produced by SOLAS An tSeirbh s Oideachais Lean naigh agus Scileanna Further Education and Training Authority In cooperation with Subject Matter Experts Martin McMahon amp CDX Global Curriculum Revision 2 2 16 01 07 SOLAS 2013 Module 3 Unit 3 Cooling System Table of Contents i BeluaraliressloyeWermererrrrrre rer crnrr ar titer A N 1 OPA Gol sock meen E ort eerie tte 2 1 0 Hazards and Safety Precautions ccccccccsseccsrsecesreeceseeeesecesseesenseeeesaes 3 1 1 Health and Safety aa rE Eiai 3 20 End of Useful Life Procedures cess sscssssassccssccsaessensacsadsontsavedsasissvseonteate 4 21 Environmental Aspects Coolant s ssessssssersesessesssessseenseesessssseees 4 3 0 The Sealed Liquid Cooling System ccccccssesssesssesseesseeseeeseseneeeeseees 4 31 Cooling SysteMsiissercccsscissisessssacsavesasscsevassivsssevisciseetesnsessceassssesaeanes 4 JA MAG GI COON Gas iectscessstesacesssntexcesadeysrasiaxusunteveivseassaqssqsezesvsraussyeeizs 6 3 3 Cooling System Hoses iisccsccscscsscesssscccserseresnssassacisascanverssanssaseeis 7 3 4 Cooling Fans Electric Viscous Hub ieereereeeeeeseeeesseeeseesesees 7 35 Cooling System Thermosta cc isscsssccssisscussesessoccssssntussesassvarssessaaioase 9 26 Elecrolys Brna cep acre rren rr ee creer eer rece cry etree tite 9 y MRACTATOR E E T gake dezevaceasesacene 1
3. Work clothing such as coveralls and steel capped footwear Eye protection such as safety glasses and face masks Ear protection such as earmuffs and earplugs Hand protection such as rubber gloves and barrier cream Respiratory equipment such as face masks etc Safety Check e Never drain and refill the cooling system of a hot engine Wait for it to cool down first Always make sure that you wear the appropriate personal protection equipment before starting the job It is very easy to hurt yourself even when the most exhaustive protection measures are taken Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 Module 3 Unit 3 Cooling System Always make sure that your work area environment is as safe as you can make it Do not use damaged broken or worn out workshop equipment Always follow any manufacturer s personal safety instructions to prevent damage to the vehicle you are servicing Make sure that you understand and observe all legislative and personal safety procedures when carrying out the following tasks If you are unsure of what these are ask your instructor Points to Note Some vehicles have drain plugs on the side of the engine block The shop service manual will tell you if these need to be opened when draining the coolant Step by step Instruction 1 Locate drain plug Locate the cooling system drain plug or valve on the bottom tank of the radiator Place a clea
4. 1 Through a solid UL 2 Through a liquid or gas LU 3 By invisible rays LU 4 From the fins of an air cooled engine to the atmosphere Q18 With a downflow radiator the coolant flow is from Tick one box only LU 1 Side to side L 2 Top to bottom LU 3 End to end UL 4 Bottom to top Q19 What is the main function of a separate recovery tank Tick one box only LU 1 To stabilize the coolant temperature LY 2 To maintain coolant in the system at all times LU 3 To increase the system s operating pressure 4 A more convenient location for adding coolant to the system Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 40 Module 3 Unit 3 Cooling System Q20 One of the functions of a radiator cap is to Tick one box only LJ 1 Increase the boiling point of the coolant in proportion to the spring tension E 2 Protect the chemical additives of some coolants from breaking down E 3 To control the temperature of the heater core LU 4 To prevent the engine coolant from boiling Q21 With a crossflow radiator the coolant flow is from Tick one box only LU 1 Side to side L 2 Top to bottom LU 3 End to top LY 4 Bottom to end Q22 The primary function for the engine water pump is to Tick one box only LU 1 Pressurize the cooling system L 2 Circulate the coolant through the engine L 3 Circulate the coolant when the thermostat is closed L 4 Pump the heated
5. Always use extreme caution when removing the radiator cap Releasing the pressure cap on an engine at operating temperature may cause the hot coolant to superheat If you must remove the radiator cap from a hot system wear protective gloves and eyewear and remove it slowly to the first safety point to prevent the pressure inside from erupting If you don t this could cause the scalding hot coolant to spill hot fluid over you or someone standing nearby Make sure the engine is off when carrying out any visual inspection of the system or when you connect the tester You may be required to run the engine after the tester has been installed and pressurized When the engine is running make sure that you keep any loose clothing away from rotating parts When pressure testing a system make sure you do not exceed the manufacturer s maximum pressure Have a qualified instructor show you the correct operation of the tester Make sure that you understand and comply with all environmental and occupational health and safety standards for your workplace at all times If you are unsure of what these are ask your instructor Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 30 Module 3 Unit 3 Cooling System Points to Note ee To test the cooling system for both internal and external leaks a pressure tester is normally used These are often referred to as cooling system testers or analyzers There are a n
6. check the radiator hoses Always make sure that you wear the appropriate personal protection equipment before starting the job It is very easy to hurt yourself even when the most exhaustive protection measures are taken Always make sure that your work area environment is as safe as you can make it Do not use damaged broken or worn out workshop equipment Always follow any manufacturer s personal safety instructions to prevent damage to the vehicle you are servicing Make sure that you understand and observe all legislative and personal safety procedures when carrying out the following tasks If you are unsure of what these are ask your instructor Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 49 Module 3 Unit 3 Cooling System Points to Note If you find one defective hose the chances are that the other hose s may be deteriorating in the same way and will soon need to be replaced For this reason most technicians will generally replace both hoses at once as a sensible precaution You may need to use a torch to inspect the coolant hoses so that you can clearly see if the surface is starting to crack Radiator Hose Problems Swollen hose This hose has lost Hardened hose This hose has its elasticity and is swelling under become brittle and will break pressure It may soon rupture and leak Cracked hose This hose has Soft hose This hose has become cracked and will soon start
7. thus quieter and absorbs less engine power There is no cowling to obstruct access to the engine The water and jackets deaden mechanical noise The engine is better able to operate under arduous conditions without overheating Disadvantages Weight not only of the radiator and connections but also of the water The whole engine installation is likely to be heavier than an equivalent air cooled engine Because the water has to be heated the engine takes longer to warm up after starting from cold If water is used the maximum temperature is limited to about 85 to 90 to avoid the risk of boiling away the water If the engine is left standing in very cold weather precautions must be taken to prevent the water freezing in the cylinder jackets and cracking them There is a constant risk of leaks developing A certain amount of maintenance is needed e g checking water level anti frost precautions cleaning out deposits etc Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 23 Module 3 Unit 3 Practical Task Objective Personal Safety Cooling System 9 0 Testing Antifreeze Solution in a Cooling System Key Learning Points Correct use of the antifreeze hydrometer to test the specific gravity of the coolant Please refer to your instructor for additional information which is available from the automotive technical manuals 9 1 Checking amp Adjusting Coolant Preparation a
8. System Points to Note There are two types of drive belts s V type A V type belt has a profile that looks like the photo below and sits inside a deep v shaped groove in the pulley wheel The sides of the V belt contact the sides of the groove Serpentine Serpentine type belts have a flat profile with a number of grooves running lengthwise along the belt These grooves are the exact reverse of the grooves in the outer edge of the pulley wheels they increase the contact surface area as well as prevent the belt from slipping off the wheel as it rotates Conditions to look for on a drive belt Cracked Cracks in a belt indicate that it is getting ready to fail and should be replaced Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 61 Module 3 Unit 3 Cooling System Oil soaked A belt that has been soaked in oil will not grip properly on the pulleys and will slip If the oil contamination is severe enough for this to happen replace the belt Glazed Glazing is shininess on the surface of the belt which comes in contact with the pulley If the belt is worn the glazing could be caused by the belt bottoming out see below and it should be replaced If it is not old and worn glazing could simply indicate that the belt is not tight enough Tightening the belt may be all that is necessary depending on how bad the glazing is Torn Torn or split belts are unserviceable and should be
9. away cooling the liquid before it returns to absorb more heat from the engine he Radiator a fins Coolant in radiator Se It can be made of sheet metal or hardened plastic The radiator has 2 tanks and a core The materials used in the radiator must be good heat conductors like brass or copper Brass and copper are often used for tanks combined with a copper core Modern vehicles often use plastic tanks combined with an aluminium core This saves weight but still provides good heat transfer The cote consists of a number of tubes that carry coolant between the 2 tanks The tubes can be in a vertical down flow pattern or a horizontal cross flow pattern Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 10 Module 3 Unit 3 Cooling System A cross flow radiator fits more easily under a steeply sloped bonnet In the core small thin cooling fins are in contact with the tubes The shape of the fins increases the surface area exposed to the air Where coolant touches tube walls and where the tubes touch the fins heat is removed from the coolant by conduction then by radiation and convection at the surface of the fins Air rushing by carries the heat away Liquid emerges cooler at the bottom of the radiator It travels through the lower radiator hose to the water pump inlet then through the engine again 3 8 Radiator Pressure Cap If a coolant boils it can be as serious for an engine as having it free
10. boiling point by 2 C For example A 90 kPa 13 PSI radiator cap will increase the boiling point from 100 C to 118 C Similarly a 100 kPa 14 5 PSI radiator cap will raise the boiling point from 100 C to 120 C Pressure testing kits come with a number of adapters for various cooling systems These adapters can be used to connect the tester to the radiator or to the radiator cap Step by Step Instruction 1 Inspect cooling system visually Before pressure testing the system visually inspect the system for any obvious signs of leaks or wear in the radiator core radiator tanks coolant and heater hoses water pump all accessible engine core plugs cooling fan drive belt and radiator cap and seals Check the operating instructions of the tester Refer to the pressure tester s manual for correct operation The outside of the radiator cap should be marked with its operating pressure When this pressure is reached the pressure relief valve in the cap will allow a discharge into the overflow system Test the radiator cap Refer to the workshop manual or vehicle owner s manual to check that the pressure cap fitted has the correct pressure rating for that cooling system Attach the radiator cap to the tester with an adaptor and pump up the pressure on the radiator cap spring The pressure should hold just below the relief pressure setting If the pressure will not hold or it cannot reach this pressure then replace it with a new c
11. of the surface of the cylinder head and this distortion can also occur to aluminium engine blocks Testing the distortion of aluminium cylinder head and of aluminium block Both should be checked using a straight edge longitudinally laterally and diagonally to highlight discrepancies outside of the recommended tolerances Cracking can also occur that may necessitate replacement of the head Always check the manufacturer s recommendations on cylinder head cracks their location and size Sometimes some cracking in certain locations may be acceptable e Reducing possibility of cylinder head warping To help avoid warp of aluminium heads the manufacturers recommendations should be followed carefully during dismantling and reassembly e g the engine should be allowed to cool down fully before attempting removal of the head all bolts should be removed in the correct sequence etc Care of the cylinder head surface The surface must not be scratched or sanded always turn the surface up when the head is left on a bench cleaning may only be done with gasket remover and wooden plastic spatula Only use gasket remover in open spaces do not inhale fumes Follow manufacturet s recommendations Cylinder head re surfacing Manufacturers may supply tolerances for the re surfacing of the cylinder head but great care and attention must be given to any re working of a cylinder head that has camshaft s running fitted in it E Damage t
12. places so that you can remove it easily Clean the hose fittings thoroughly on both the engine and the radiator with fine sandpaper or emery cloth so that it will make a good seal with the new hose 3 Verify replacement Obtain new hoses and compare them with the removed hoses to make sure they are the same length and diameter If the hose is a moulded type the new one must also have the same pre formed curve Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 51 Module 3 Unit 3 Cooling System Refit hose Apply some sealing compound to the hose fittings and place the loosened clamps over the hose ends before sliding the hose into position on the block and radiator fittings Tighten the clamps securely about a quarter of an inch or 6mm from the end of the hose Be careful not to over tighten and damage the hoses but it is important they do not fall off once the pressure in the cooling system increases Refill cooling system and check Refill the cooling system and then run the engine for a few minutes Check the hose connections to make sure that there are no leaks When the engine is at its normal operating temperature check the tightness of the clamps again as the clamps and hoses will both expand at different rates as they heat up Testing Cooling System Pressure Preparation and Safety Objective Test a cooling system to confitm that it is without leaks and has the ability to hold the pressure sp
13. proper safety procedures are not adhered to when working on the Coo ing System this could lead to burns scalding injuries from moving parts and slips amp falls from coolant leaking onto floor Instruction is given in the proper safety procedures applicable to working on cooling systems which include the following key points Boiling liquid Pressure cap removal e Rotating fans pulleys Automatic fan cut in Engine overheating damage Water leaks Refer to motor risk assessments Environmental policy and Material Safety Data Sheets MSDS Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 Module 3 Unit 3 Cooling System 2 0 End of Useful Life Procedures 2 1 Environmental Aspects Coolant When disposing of used coolant care must be taken not to cause pollution Storage of used coolant must comply with the currant law regarding environment protection Coolant must be disposed of by an authorised waste disposal company 3 0 The Sealed Liquid Cooling System 3 1 Cooling Systems Combustion of the air fuel mixture in the cylinders generates heat which produces high pressure to force the piston down in the power stroke Not all of this heat can be converted into useful work on the piston and it must be removed to prevent seizure of moving parts This is the role of the cooling system Most engines are liquid cooled Trade of Motor Mechanic Phase 2 Course Notes Revis
14. worn out workshop equipment Always follow any manufacturer s personal safety instructions to prevent damage to the vehicle you are servicing Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 47 Module 3 Unit 3 Cooling System Make sure that you understand and observe all legislative and personal safety procedures when carrying out the following tasks If you are unsure of what these are ask your instructor Points to Note Some vehicles have drain plugs on the side of the engine block The shop service manual will tell you if these need to be opened when draining the coolant Step by Step Instruction 1 Locate drain plug Locate the cooling system drain plug or valve on the bottom tank of the radiator Place a clean drain pan large enough to contain all the coolant underneath the drain valve Drain radiator Carefully remove the radiator pressure cap This will allow air into the cooling system so that it can drain quickly and completely Open the drain valve so that the coolant can drain into the pan below When all the coolant has drained out close the drain valve Refill coolant system Check the shop service manual for the capacity of the system and the recommended type and mixture of coolant for the operating conditions of the vehicle Measure the recommended amount of coolant and using a funnel pour it in through the top of the radiator Start engine and verify Ait can be trapped in t
15. 0 38 Radiator Pressure Cap sccssvesscsvescscsesssssivsssestsnesssceensamansran ses 11 BD Recovery Yle Oiana E EE 12 3 10 Temperature Indicators assis sccssssssssssssessnstessscessdesssonsezseseeasicosa iia 12 3 11 Thermo Switch Bi Metal Switch sseesssesesssssoessoseeesessssssseeese 13 312 Water Pump assia EE A N E 14 3 13 Centrifugal Force isssiscscsssscossseassscscsscsscssseasecasssssesonacaassecesasessssxciss 14 4 0 Mechanically Driven Fan Forced Air Engine Cooling System 15 di T Oo T aT O E E 15 5 0 Heat Transfer Conduction Convection and Radiation eeeenneeeeeeenee 16 Delt eatae E a a a E aT RA 16 5 2 Temperature and Temperature Scales eeeeeeeeeeeeeeseeeeseeseessensa a7 6 0 Testing Cooling System Component e seesesssesesssessersssseessessessesseesensse 18 61 Removing amp Replacing a Thermostat eeeeeeeeeeeereeeeeeseesessseese 18 10 The Boiling Point OF Water sicsscsasisssssxeescesssssssavssvassgasvecsssnsssassveasssanesssese 21 7 1 Boiling Point and Pressure ccccssecessseeesseeeeseeeeseeeesseeeseneeeses 21 8 0 Comparison of Liquid and Air Cooling Systems eeeeeeeeeseeesneesseeesee 22 8 1 Ait Cooled Pina vesississssecesdscccicscscisuac cesses tacts canedesssnesiosiseceancersieals 22 82 Liquid Cooled Ende Suuria 23 9 0 Testing Antifreeze Solution in a Cooling System ieeeeeeeeseeseeseseeesees 24 91 Checking amp Adjusting Coolant c cssccssnssncs
16. Prevents the coolant freezing Q6 The thermostat in an engine cooling system controls Tick one box only LU 1 Pressurization of the system L 2 Operation of the electric fan L 3 Circulation of coolant to the heater L 4 Circulation of coolant to the radiator Q7 A by pass is incorporated in a cooling system to Tick one box only LJ 1 Raise the boiling point of the water 2 Prevent the radiator hoses from collapsing on engine cooling LJ 3 Allow the coolant to by pass to the radiator when the y p pressure becomes excessive 4 Allow the coolant to circulate through the engine when the thermostat is closed Q8 Some modern coolants are developed from organic ma terials Tick one box only LJ 1 True L 2 False Q9 Cooling fins on the cylinders of an air cooled engine Tick one box only L 1 Reduce engine noise 2 Reduce the severity of burns 3 Provide increased surface area OOo 4 Improve engine strength Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 38 Module 3 Unit 3 Cooling System Q10 All coolants are designed to change colour as they get older as an indication of loss of effectiveness Tick one box only L 1 True L 2 False O11 The purpose of the viscous clutch on the fan hub is to Tick one box only CL a Improve cooling at high road speeds U 2 Extend engine warm up time L 3 Reduce engine power loss and noise L 4 Reduce under b
17. adiation Key Learning Points e Definition of heat movement conduction convection and radiation temperature and temperature scales Celsius Kelvin 5 1 Heat transfer The internal combustion engine works by changing heat energy into kinetic energy There are many ways to do this some better than others But no matter how efficiently it is done and no matter the size of the engine the heat energy generated never completely changes into kinetic energy Some energy is always lost Radiation This is certainly true in internal combustion engines where only about a third of the heat generated is transformed into the mechanical energy that moves the piston and turns the crankshaft Another third goes out the exhaust wasted The rest tries to spread round the engine Heat always moves from areas of higher temperature to areas of lower temperature which can be a problem To control this movement it is necessary to understand how heat is transferred Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 16 Module 3 Unit 3 Cooling System Heat travels in just 3 ways The way it moves through solids is called conduction Through liquids and gases it is called convection It follows paths called convection currents Through space it moves by radiation 5 2 Temperature and Temperature Scales Temperature definition The degree of hotness or coldness of a body or environment The degree Celsi
18. adiator cap should be marked with its operating pressure When this pressure is reached the pressure relief valve in the cap will allow a discharge into the overflow system Test the radiator cap Refer to the workshop manual or vehicle owner s manual to check that the pressure cap fitted has the correct pressure rating for that cooling system Attach the radiator cap to the tester with an adaptor and pump up the pressure on the radiator cap spring The pressure should hold just below the relief pressure setting If the pressure will not hold or it cannot reach this pressure then replace it with a new cap of the correct type and recommendation Test the cooling system Before testing the integrity of the cooling system top up the coolant level Attach the cooling system tester to the radiator cap locator Pump up the system pressure to slightly above the pressure recommended by the rating specified on the pressure relief cap Observe the pressure reading If it remains steady and does not drop then the system is not leaking However if the pressure drops look for the leak If there is no visible external leak then the leak is most probably internal If there are any visible leaks or the pressure drops refer you test results to your instructor Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 32 Module 3 Unit 3 Cooling System 13 0 Overheating or Overcooling 13 1 Causes of Engine Overheating Th
19. an make it Do not use damaged broken or worn out workshop equipment Always follow any manufacturer s personal safety instructions to prevent damage to the vehicle you are servicing Make sure that you understand and observe all legislative and personal safety procedures when carrying out the following tasks If you are unsure of what these are ask your instructor There ate two correct level marks on the reservoir because the coolant in the system expands and contracts in volume depending on how hot it is The coolant level should be at the lower mark when the vehicle is cold The coolant level should be at the upper mark when the coolant is hot Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 25 Module 3 Unit 3 Cooling System If the reservoir is completely empty add coolant until the level is up to the appropriate mark for the engine temperature Then run the engine until it is at its normal operating temperature and check the level again You will probably need to adjust the level again For each 10 kPa increase in the radiator cap operating pressure it will increase the boiling point of the coolant by 2 C Step by Step Instruction 1 Check fluid level Most modern vehicles have a coolant system that uses a transparent recovery tank as a coolant reservoir Check the level of coolant in this reservoir if the engine is hot the level should be visible at the upper mark If the eng
20. ap of the correct type and recommendation Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 Module 3 Unit 3 Cooling System Test the cooling system Before testing the integrity of the cooling system top up the coolant level Attach the cooling system tester to the radiator cap locator Pump up the system pressure to slightly above the pressure recommended by the rating specified on the pressure relief cap Observe the pressure reading If it remains steady and does not drop then the system is not leaking However if the pressure drops look for the leak If there is no visible external leak then the leak is most probably internal If there are any visible leaks or the pressure drops refer you test results to your instructor Removing amp Replacing a Radiator Preparation and Safety Objective Safely remove and replace a radiator Personal Safety Whenever you perform a task in the workshop you must use personal protective clothing and equipment that is appropriate for the task and which conforms to your local safety regulations and policies Among other items this may include Safety Check Work clothing such as coveralls and steel capped footwear Eye protection such as safety glasses and face masks Ear protection such as earmuffs and earplugs Hand protection such as rubber gloves and barrier cream Respiratory equipment such as face masks etc Coolant in the cooling system co
21. ard to the cylinder head Manufacturer remedies to avoid temperature rise due to heat soak A small electric water pump may be fitted that will switch on automatically should the temperature rise excessively due to heat soak after the engine has been switched off This pump will then circulate the coolant through the system which will distribute the unwanted heat away Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 33 Module 3 Unit 3 Cooling System Faulty cylinder head gasket As the head gasket gradually becomes faulty the initial movement will consist of only molecules of combustion gas that creep unnoticed into the coolant Eventually the amount of hot gases entering affect the operation of the cooling system creating bubbles of hot gas that raise both the temperature and pressure inside the system The engine eventually begins to boil overheat and lose coolant The more coolant is lost the faster the temperature will rise Hydraulic lock Hydraulic lock is the term used to describe the locking solid of the engine due to its inability to compress a liquid inside the combustion chamber This problem particularly affects diesel engines with their high compression ratios and therefore very small combustion chamber volumes The effect of water intake into the combustion chamber is often seen in times of severe road flooding as drivers of diesel powered vehicles drive too quickly thr
22. ave the engine mounted on flexible mountings to reduce noise and vibration Since the radiator is mounted to the vehicle body flexible hoses are needed Coolant is also carried to the heating system which is usually inside the cabin of the vehicle Coolant hoses vary in diameter depending on the volume of coolant that passes through them Heater hoses carry a smaller volume All hoses are subject to hot coolant and high under bonnet temperatures and they can deteriorate and fail 3 4 Cooling Fans Electric Viscous Hub In a vehicle moving at high speed airflow through the radiator cools the coolant but at low speed or when the engine is idling extra airflow comes from a fan Fans can be driven in different ways More and more modern vehicles now use an electric fan Air conditioned cars often have extra fans Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 Module 3 Unit 3 Cooling System Electric fans can be behind the radiator in front or both This arrangement would be difficult with a belt driven fan Some fans can be driven from the crankshaft When an engine is mounted longitudinally its fan is usually mounted on the water pump shaft The drive belt then turns the water pump and fan Some use a hydraulic link from the power steering system Fan blades can be rigid or flexible Rigid blades tend to be noisy and use more energy This noise can be reduced by using irregular spacing of the fan bla
23. coolant into the heater core Q23 A vehicle coolant inhibitor needs to prevent 3 condi tions These conditions are Tick one box only LU 1 Over heating corrosion and staining 2 Freezing corrosion and staining L 3 Freezing over heating and corrosion L 4 None of these Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 41 Module 3 Unit 3 Cooling System Q24 When overhauling an air cooled engine it is necessary to ensure that all fins are clean and intact to Tick one box only LU LU LU LU 1 Stop dilution of the eneine 2 Assist the engine in warming up 3 Prevent oil leaks 4 Maintain correct heat transfer Q25 An engine operating at well below the designed operat ing temperature will Tick one box only LU LU LU LU 1 Produce the same power as an engine operating at the correct temperature 2 Increase cylinder piston and piston ring wear 3 Have no detrimental effect on engine life 4 Enable a longer useful life for engine lubricating oil Q26 Removing the radiator cap of a hot engine may cause Tick one box only LU OOo 1 The bottom hose to collapse 2 The engine to seize due to a sudden rise in temperature 3 Immediate boiling of the coolant 4 Damage to the radiator core Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 42 Module 3 Unit 3 Cooling System Suggested Exercises T Use an electronic data fac
24. des Some vehicles use a shroud to direct all of the air that the fan moves through the radiator core At high speeds plenty of air is already flowing through the radiator If the fan is always working at full speed it s a waste of energy and since the engine drives the fan it s a waste of fuel too What s needed is some way to control the fan A heat sensitive switch in contact with the coolant can work like a thermostat and turn the fan on and off according to coolant temperature Another way to alter the speed of the fan is with a viscous hub This type of fan slips when it is cold but as the engine heats up it grips more and more Testing of this hub can only be done following manufacturers instructions The drive has a disc shaped clutch plate that is placed in a container of silicone fluid The viscous drag of the fluid caused by its resistance to shear provides a non positive drive that is designed to slip at an increasing rate as the engine speed rises Viscous fans are made in two forms torque Limiting and air temperature sensitive Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 Module 3 Unit 3 Cooling System 3 5 Cooling System Thermostat The thermostat helps an engine to warm up It s found in different positions on different engines It is a valve that operates according to coolant temperature When coolant is cold a spring holds the valve closed When a cold engine starts coolant c
25. ecified by the manufacturer Personal Safety Whenever you perform a task in the workshop you must use personal protective clothing and equipment that is appropriate for the task and which conforms to your local safety regulations and policies Among other items this may include Safety Check Work clothing such as coveralls and steel capped footwear Eye protection such as safety glasses and face masks Ear protection such as earmuffs and earplugs Hand protection such as rubber gloves and barrier cream Respiratory equipment such as face masks etc When working around the cooling system care must be taken particularly if the engine is at operating temperature as the coolant may be hot enough to scald Always allow the system to cool before removing the radiator cap Do not remove a radiator cap from a hot cooling system Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 Module 3 Unit 3 Points to Note Cooling System Always use extreme caution when removing the radiator cap Releasing the pressure cap on an engine at operating temperature may cause the hot coolant to superheat If you must remove the radiator cap from a hot system wear protective gloves and eyewear and remove it slowly to the first safety point to prevent the pressure inside from erupting If you don t this could cause the scalding hot coolant to spill hot fluid over you or someone standing nearby Make s
26. em with coolant Run the engine to circulate the coolant and remove any air trapped in the system Check that the temperature indicator gauge shows the coolant temperature is in the normal operational range Top up the radiator or reservoir with coolant if necessary Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 20 Module 3 Unit 3 Cooling System 7 0 The Boiling Point of Water Key Learning Points e Ambient pressure pressure caps boiling point of water 7 1 Boiling Point and Pressure Water at atmospheric pressure at sea level boils at 100 degrees Celsius That is it s boiling point Atmospheric Pressure If the water is put under pressure higher than atmospheric pressure it boils at a higher temperature If the pressure is decreased below sea level atmospheric pressure it boils at a lower temperature Therefore raising pressure above atmospheric pressure increases the boiling point Lowering it below atmospheric pressure lowers the boiling point Changing water pressure changes the temperature at which it boils Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 21 Module 3 Unit 3 Cooling System 8 0 Comparison of Liquid and Air Cooling Systems 8 1 Air Cooled Engines Listed here are some advantages and disadvantages Advantages An air cooled engine should generally be lighter than the equivalent water cooled engine The engine warms up t
27. ere are a number of reasons why an engine is running hot overheating and showing an indication much higher that the normal range on the temperature gauge Listed here are a few reasons Low coolant levels The quantity of coolant present in the system is the first possible cause of overheating How or why the level of coolant dropped is next Is it simply leaking or is it being boiled off due to faulty thermostat head gasket or other fault Check all possible external and internal hoses and clips etc Faulty thermostat As you have seen Testing of the thermostat the thermostat can fail in the open or shut positions more usually in the open position If the thermostat is a combined wax and electrically operated a malfunction will trigger an EOBD fault code e g PO116 7 8 and 9 8 Stresses on the cylinder head gasket The head gasket fitted between the block and cylinder head seals in combustion gases pressures coolant and oil However the cylinder head and engine block can be affected by differing rates of thermal expansion superficial expansion The manufacturer will do the best to neutralize this movement by good design but the head gasket may still subjected to movement especially if the temperatures become excessive Excessive temperatures can occur even after the engine has been switched off due to heat soak t e lack of movement of the coolant and the soaking of combustion chamber temperatures outw
28. he cooling system so leave the radiator cap off to allow it to escape and run the engine for a few minutes to allow the coolant to circulate and get rid of trapped air Then replace the radiator cap and bring the engine up to operating temperature Check the coolant level in the reservoir and top it up to the high or hot engine mark Dispose of waste Antifreeze is toxic so dispose of the waste coolant carefully and in an environmentally recommended way Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 48 Module 3 Unit 3 Cooling System Checking amp Replacing a Coolant Hose Preparation and Safety Objective Check remove and replace coolant hoses Personal Safety Whenever you perform a task in the workshop you must use personal protective clothing and equipment that is appropriate for the task and which conforms to your local safety regulations and policies Among other items this may include Safety Check Work clothing such as coveralls and steel capped footwear Eye protection such as safety glasses and face masks Ear protection such as earmuffs and earplugs Hand protection such as rubber gloves and barrier cream Respiratory equipment such as face masks etc Never try to assess the serviceability of a coolant hose while the engine is hot Let it cool down so that you can handle the hoses comfortably and safely Always ensure the engine is turned off before attempting to
29. ific heat capacity which means that it has a good ability to absorb heat It is this ability to absorb large quantities of unusable heat from around the engine cylinders retain the heat and carry it to the radiator where the high temperature coolant is exposed to air at a lower temperature and as heat always flows from a high temperature to lower temperature the heat energy is dissipated and the temperature of the water is reduced This system is known as thermo siphon In modern cars the engines are more powerful therefore radiators are low and wide and a thermo siphon process couldn t move the coolant quickly enough Instead a water pump forces it through passages called water jackets in the engine block It collects heat by conduction and becomes hot itself Heated coolant then returns to the radiator for cooling and the cycle is repeated Heat is removed from the engine and dispersed Preventing overheating is one function of the cooling system It also helps the engine reach its best operating temperature as soon as possible Every engine has a temperature at which it operates best Below this temperature ignition and combustion can be difficult Most engine wear occurs during this warm up period and most pollution too Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 Module 3 Unit 3 Cooling System 3 3 Cooling System Hoses Coolant is transferred throughout the cooling system by hoses Most vehicles h
30. ility to procure manufacturer s appropriate data for use with practical exercises Remove refit replace cooling system components Test operation of the thermostat refill bleed system and check for leaks Test the specific gravity of antifreeze Test the operation of the cooling fan and thermo switch Training Resources Technical information in book electronic form on heat and temperature changes of state of engine coolant i e boiling and freezing temperatures internal combustion engine air and liquid cooling systems Training vehicles units for practical exercises Cooling system test kits Antifreeze hydrometer Used coolant collection recycling disposal facility Manufacturer s data Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 43 Module 3 Unit 3 Cooling System Task Sheets Checking amp Adjusting Coolant Preparation and Safety Objective Check and adjust coolant levels and test coolant quality in a vehicle with a recovery reservoir Personal Safety Whenever you perform a task in the workshop you must use personal protective clothing and equipment that is appropriate for the task and which conforms to your local safety regulations and policies Among other items this may include Work clothing such as coveralls and steel capped footwear s Eye protection such as safety glasses and face masks Ear protection such as earmuffs and earplugs Hand protection such as r
31. in to melt The engine is now about to seize up A total rebuild is now required Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 36 Module 3 Unit 3 Cooling System Self Assessment Q1 Which method of heat transfer is prevented by heat shields fitted to the exhaust on some vehicles Tick one box only LY 1 Conduction LU 2 Convection LU 3 Induction U 4 Radiation Q2 Cross flow radiators are fitted to many modern vehicles because they Tick one box only L 1 Allow a low bonnet line to be achieved LU 2 Are cheaper to manufacture U 3 Are more efficient than vertical flow types LJ 4 Are more efficient on transverse engine vehicles Q3 Natural circulation of coolant in a cooling system is called Tick one box only LJ 1 Induction thermo flow LI 2 Convention circulation L 3 Thermo flow U 4 Thermo siphon O4 Adequate air circulation over the fins of an air cooled stationary engine is provided by Tick one box only LJ 1 Convection currents as the fins heat up LU 2 An engine driven fan Q 3 Natural air movement 4 Heat radiating to the lubricating oil Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 37 Module 3 Unit 3 Cooling System Q5 The thermostat in an engine cooling system Tick one box only LU 1 Assists the engine to warm up quickly L 2 Prevents coolant loss LJ 3 Switches on the electric cooling fan LU 4
32. ine is cold it should be at the lower mark Check protection level with a hydrometer Before adding new coolant check the specific gravity of the coolant in the system with a coolant hydrometer Draw some coolant up into the hydrometer and read the mark on the float at the level of the fluid in the chamber This will indicate the freezing point of the coolant mixture in the system so you can tell if it has the right proportions of antifreeze and water Adjust fluid level Check the service manual for the recommended type and mixture of coolant that will produce an appropriate level of protection for the conditions where the vehicle will be used Use a funnel to add enough coolant to bring the level up to the appropriate mark Replace the coolant reservoir cap Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 26 Module 3 Unit 3 Cooling System 10 0 Servicing the Cooling System Practical Task Pase refer to your instructor for additional information which is available from the automotive technical manuals 10 1 Draining amp Refilling Coolant Preparation and Safety Objective Drain cooling system and refill with correct mixture of engine coolant Personal Safety Whenever you perform a task in the workshop you must use personal protective clothing and equipment that is appropriate for the task and which conforms to your local safety regulations and policies Among other items this may include
33. ing an Engine Drive Belt Preparation and Safety Objective Inspect and manually adjust engine accessory drive belts Personal Safety Whenever you perform a task in the workshop you must use personal protective clothing and equipment that is appropriate for the task and which conforms to your local safety regulations and policies Among other items this may include Safety Check Work clothing such as coveralls and steel capped footwear Eye protection such as safety glasses and face masks Ear protection such as earmuffs and earplugs Hand protection such as rubber gloves and barrier cream Respiratory equipment such as face masks etc Never try to inspect belts with the engine running Always make sure that you wear the appropriate personal protection equipment before starting the job It is very easy to hurt yourself even when the most exhaustive protection measures are taken Always make sure that your work area environment is as safe as you can make it Do not use damaged broken or worn out workshop equipment Always follow the manufacturer s personal safety instructions to prevent damage to the vehicle you are working on Make sure that you understand and observe all legislative and personal safety procedures when carrying out the following tasks If you are unsure of what these are ask your instructor Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 60 Module 3 Unit 3 Cooling
34. ion 3 0 November 2013 Module 3 Unit 3 Cooling System A iquid cooled system uses coolant a fluid that contains special chemicals mixed with water Coolant flows through passages in the engine and through a radiator The radiator accepts hot coolant from the engine and lowers its temperature Air flowing around and through the radiator takes heat from the coolant The lower temperature coolant is returned to the engine through a pump Air cooling is common on smaller internal combustion engines Some engines use cooling fins Their design makes the exposed surface area as large as possible which allows more heat energy to radiate away and be carried off in convection currents in the air Some engines also use a fan to direct air over the fins Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 Module 3 Unit 3 Cooling System 3 2 Liquid Cooling Hot water x El 4 Q Mai bas 2 Oo so 2 _ oO Q gt O O Thermo Siphon System In the very basic liquid cooling system a coolant is stored in a radiator and in the engine As the engine heats up a natural circulation starts as coolant rises through the engine block by convection It passes through the top hose and into the radiator Inside the radiator heat is removed from the coolant as it falls from the top to the bottom When it reaches the bottom it returns to the engine through the lower radiator hose Water has a high spec
35. iquid outward Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 14 Module 3 Unit 3 Cooling System 4 0 Mechanically Driven Fan Forced Air Engine Cooling System 4 1 Air Cooling Air cooling is common on smaller internal combustion engines They may be small but they still generate a lot of heat It s the air that does the work of keeping them cool so an air cooling system is usually simple That s useful on an engine where weight is important and it works best on the engine that s exposed to a high airflow Some engines use what are called cooling fins Their design makes the exposed surface area as large as possible which allows more heat energy to radiate away and be carried off in convection currents in the air Mote air flows over the fins and more heat is carried away For a vehicle moving at speed airflow over the engine is high At low speeds or during idling heat builds up Then the engine can use some help Air should always be able to flow over the engine effectively One way to remove heat is to use a fan with shrouds and ducts to direct air to the cylinders There are many places to mount a fan and many ways to drive it For instance in some engines it s on the flywheel driven by fan belts off the crankshaft Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 Module 3 Unit 3 Cooling System 5 0 Heat Transfer Conduction Convection and R
36. irculates within the engine block and cylinder head and through a coolant bypass to the water pump inlet It can t get to the radiator As the engine warms up the coolant in the engine gets hotter and hotter Thermostats have a small hole or valve to let out air that was trapped in the engine block Heated coolant is pumped from an outlet in the cylinder head It goes into the upper radiator hose then to the radiator 3 6 Electrolysis In chemistry and manufacturing electrolysis is a method of separating bonded elements and compounds by passing an electric current through them Electrolysis is a chemical and electrical process It occurs when two different metals are in contact in the presence of a moist agent such as water One of the metals is corroded away This can occur even in pure water Immersed in this water are 2 plates one of aluminium alloy the other of cast iron The atomic structure of aluminium means it loses electrons easily leaving behind aluminium ions which are positively charged Negative oxygen ions in the water are then attracted to the aluminium ions and they join Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 Module 3 Unit 3 Cooling System to form deposits of aluminium oxide As a result the aluminium alloy is eaten away or corroded Electrolysis 3 7 Radiator Many radiators are mounted at the front of the vehicle in the path of greatest airflow The air carries heat
37. ition Tom Denton ISBN 0750662190 Automotive Mechanics 10th Edition William H Crouse and Donald L Anglin ISBN 0028009436 Bosch Automotive Electrics Automotive Electronics Systems and Components 4th Edition Robert Bosch ISBN 0837610508 Bosch Automotive Handbook 6th Edition Robert Bosch ISBN 1860584748 Bosch Automotive Technology Technical Instruction booklet series numerous titles Hillier s Fundamentals of Motor Vehicle Technology Book One 5th Edition VA W Hillier and Peter Coombes ISBN 0748780823 Hillier s Fundamentals of Motor Vehicle Technology Book Two 5th Edition V A W Hillier and Peter Coombes ISBN 0748780998 Modern Automotive Technology James E Duffy ISBN 1566376106 Motor Vehicle Craft Studies Principles EK Sully ISBN 040800133X National Car Test NCT Manual Department of Transport Vehicle Testers Manual DoT VTM Department of Transport Transmission Chassis and Related Systems Vehicle Maintenance and Repair Series Level 3 3rd Edition John Whipp and Roy Brooks ISBN 186152806X Vehicle and Engine Technology 2nd Edition Heinz Heisler ISBN 0340691867 http www cdxglobal com http auto howstuffworks com http www autoshop101 com http www cdxetextbook com Automotive Encyclopedia and Text Book Resource CD version of e textbook Available from your instructor Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 65 No
38. ition the thermostat air bleed valve if fitted in the proper position Make sure the thermostat is fully seated in the groove and stays there before fitting the housing Failure to do so will damage the new thermostat and possibly break the housing as it is tightened up Tighten the housing bolts to the correct torque Make sure to use the manufacturer s procedure to properly bleed all air from the cooling system Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 19 Module 3 Unit 3 Cooling System Step by step Instruction 1 Remove the thermostat Unbolt the thermostat housing from the engine block Be very careful not to damage the housing as it is generally made from aluminium or a similar fragile material Remove the thermostat Inspect the mating surfaces Inspect the thermostat housing and remove any gasket material from the mating surface of the housing Inspect the engine block and remove any gasket material from its mating surface Install the new thermostat Inspect the new thermostat to ensure that the identification number is the same as the one you have removed Fit the new thermostat ensuring the air bleed hole is in the correct position Check the thermostat is fully seated in its groove Fit the correct type of gasket for the vehicle you are working on Carefully refit the thermostat housing to the engine block and bolt it into place Refill the cooling system Refill the syst
39. le for reinstallation in the vehicle If the radiator fins are blocked by debris carefully clean the fins with a dry brush If the radiator is damaged advise your instructor so a decision can be made whether to repair it or replace it Replace the radiator Place the radiator into position and replace the securing bolts or screws Refit the cowlings or covers Rotate the fan and belts by hand to check the covers do not restrict movement Attach the coolant hoses to the radiator Refill the system And refill the system with new coolant of the correct type Run the engine to circulate the coolant and remove any air trapped in the system Check that the temperature indicator gauge shows the coolant temperature is in the normal operational range Top up the radiator or reservoir with coolant if necessary Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 57 Module 3 Unit 3 Cooling System Removing amp Replacing a Thermostat Preparation and Safety Objective Safely remove and replace a cooling system thermostat Personal Safety Whenever you perform a task in the workshop you must use personal protective clothing and equipment that is appropriate for the task and which conforms to your local safety regulations and policies Among other items this may include Safety Check e Work clothing such as coveralls and steel capped footwear Eye protection such as safety glasses and face masks Ear protec
40. n drain pan large enough to contain all the coolant underneath the drain valve Drain radiator Carefully remove the radiator pressure cap This will allow air into the cooling system so that it can drain quickly and completely Open the drain valve so that the coolant can drain into the pan below When all the coolant has drained out close the drain valve Refill coolant system Check the shop service manual for the capacity of the system and the recommended type and mixture of coolant for the operating conditions of the vehicle Measure the recommended amount of coolant and using a funnel pour it in through the top of the radiator Start engine and verify Air can be trapped in the cooling system so leave the radiator cap off to allow it to escape and run the engine for a few minutes to allow the coolant to circulate and get rid of trapped air Then replace the radiator cap and bring the engine up to operating temperature Check the coolant level in the reservoir and top it up to the high or hot engine mark Dispose of waste Antifreeze is toxic so dispose of the waste coolant carefully and in an environmentally recommended way Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 28 Module 3 Unit 3 Practical Task Practical Task Objective Personal Safety Cooling System 11 0 Testing Viscous Coupling and a Bi Metal Switch The testing of the radiator fan thermo switch circuit has to be do
41. nd Safety Check and adjust coolant levels and test coolant quality in a vehicle with a recovery reservoir Whenever you perform a task in the workshop you must use personal protective clothing and equipment that is appropriate for the task and which conforms to your local safety regulations and policies Among other items this may include Work clothing such as coveralls and steel capped footwear Eye protection such as safety glasses and face masks Ear protection such as earmuffs and earplugs Hand protection such as rubber gloves and barrier cream a Respiratory equipment such as face masks etc Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 24 Module 3 Unit 3 Safety Check Points to Note Cooling System Always be very careful when opening a radiator cap because the cap keeps the coolant under pressure to raise its boiling point Sometimes even the pressure in a warm engine can force the coolant to spurt out when the cap is released Always cover the radiator cap with a rag to catch any hot spray Always wear eye protection Never open a radiator cap on an overheated engine wait for it to cool down first Always make sure that you wear the appropriate personal protection equipment before starting the job It is very easy to hurt yourself even when the most exhaustive protection measures are taken Always make sure that your work area environment is as safe as you c
42. nd equipment that is appropriate for the task and which conforms to your local safety regulations and policies Among other items this may include Work clothing such as coveralls and steel capped footwear Eye protection such as safety glasses and face masks Ear protection such as earmuffs and earplugs i Hand protection such as rubber gloves and barrier cream Respiratory eguipment such as face masks etc Coolant in the cooling system could be above its boiling point Never open a radiator cap fully until ALL pressure has been Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 18 Module 3 Unit 3 Points to Note Cooling System released Before removing the pressure cap check the temperature of the cooling system with an infrared temperature gun if you have one available When removing a radiator cap use appropriate gloves clothes full face shield etc Before commencing a repair or service task on the cooling system and allow approximately 30 minutes for the system to cool sufficiently before opening the pressurised system When removing a radiator cap use appropriate gloves clothes full face shield etc Make sure that you understand and observe all legislative and personal safety procedures when carrying out the following tasks If you are unsure of what these are ask your instructor Drain the at least 50 of the coolant in the system to avoid spills Pos
43. ne according to manufactures specification Please refer to your instructor for additional information which is available from the automotive technical manuals 12 0 Cooling System Components and Pressure Test Please refer to your instructor for additional information which is available from the automotive technical manuals 12 1 Testing Cooling System Pressure Preparation and Safety Test a cooling system to confirm that it is without leaks and has the ability to hold the pressure specified by the manufacturer Whenever you perform a task in the workshop you must use personal protective clothing and equipment that is appropriate for the task and which conforms to your local safety regulations and policies Among other items this may include Work clothing such as coveralls and steel capped footwear Eye protection such as safety glasses and face masks Ear protection such as earmuffs and earplugs i Hand protection such as rubber gloves and barrier cream Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 Module 3 Unit 3 Safety Check Cooling System Respiratory equipment such as face masks etc When working around the cooling system care must be taken particularly if the engine is at operating temperature as the coolant may be hot enough to scald Always allow the system to cool before removing the radiator cap Do not remove a radiator cap from a hot cooling system
44. o its normal running temperature very quickly The engine can operate at a higher temperature than a water cooled engine The system is free from leakage problems and requires no maintenance There is no risk of damage due to freezing of the coolant in cold weather Disadvantages A fan and suitable cowls are necessary to provide and direct the airflow The fan is noisy and absorbs a fairly large amount of engine power The cowling makes it difficult to get at certain parts of the engine The engine is more liable to overheating under arduous conditions than a water cooled engine Mechanical engine noises tend to be amplified by the fins The cylinders usually have to be made separately to ensure proper formation of the fins This makes the engine more costly to manufacture Cylinders must be spaced well apart to allow sufficient depth of fin It is more difficult to arrange a satisfactory passenger compartment heating system Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 22 Module 3 Unit 3 Cooling System 8 2 Liquid Cooled Engines Listed here are some advantages and disadvantages Advantages Temperatures throughout the engine are more uniform thus distortion is minimized Cylinders can be placed close together and the engine made more compact Although a fan is usually fitted to force air through the radiator it is smaller than that required in an air cooled system and is
45. o the short block due to overheating Short block is the term used to describe the engine block and all its internal components e g crankshaft pistons etc The most serious result that overheating can have on this is over expansion of the pistons Severe overheating inevitably means that the rear pistons which have the least supply of low temperature coolant expand until they no longer can fit comfortably inside the cylinder Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 35 Module 3 Unit 3 Cooling System Why the pistons at the rear are first to melt Remember the water pump is always in the front of the engine with its impeller driving the cool water that is returning from the radiator from the front cylinders to the further cylinders at the rear As the coolant travels back through the engine it is gaining heat all the time Should the coolant level get low bubbles and air pockets form around the cylinders these reduce the effectiveness of the coolant the temperatures rise abnormally Eventually the pistons get tight in the cylinder bore friction increases and the pistons begin to melt Crankshaft damage At the same time as some pistons are getting tight in the cylinders others are working away pushing and dragging the tight pistons up and down the bores this causes excessive pressures on the crankshaft bearings where friction now increases and the shell bearings overheat and beg
46. ommended type and mixture of coolant that will produce an appropriate level of protection for the conditions where the vehicle will be used Use a funnel to add enough coolant to bring the level up to the appropriate mark Replace the coolant reservoir cap Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 46 Module 3 Unit 3 Cooling System Draining amp Refilling Coolant Preparation and Safety Objective Drain cooling system and refill with correct mixture of engine coolant Personal Safety Whenever you perform a task in the workshop you must use personal protective clothing and equipment that is appropriate for the task and which conforms to your local safety regulations and policies Among other items this may include Safety Check Work clothing such as coveralls and steel capped footwear Eye protection such as safety glasses and face masks Ear protection such as earmuffs and earplugs Hand protection such as rubber gloves and barrier cream Respiratory equipment such as face masks etc Never drain and refill the cooling system of a hot engine Wait for it to cool down first Always make sure that you wear the appropriate personal protection equipment before starting the job It is very easy to hurt yourself even when the most exhaustive protection measures are taken Always make sure that your work area environment is as safe as you can make it Do not use damaged broken or
47. onnet temperatures Q12 The 2 valves incorporated in the radiator cap are Tick one box only LJ 1 The pressure and regulator valves L 2 The vacuum and pressure valves LU 3 The regulator and vacuum valves LU 4 The temperature and pressure valves Q13 Cooling systems are pressurized to Tick one box only CL 1 Improve coolant circulation LJ 2 Prevent internal coolant leaks L 3 Raise the boiling point of the coolant LU 4 Increase the warm up period Q14 The vacuum valve in the radiator cap Tick one box only U 1 Maintains a vacuum in the system at all times L 2 Prevents a vacuum occurring as the engine cools LU 3 Prevents air entering the system 4 Allows thermo siphon circulation of the coolant Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 39 Module 3 Unit 3 Cooling System Q15 Special chemicals are added to the water in an engine cooling system to Tick one box only L 1 Lower its boiling point LJ 2 Prevent foaming and evaporation L 3 Prevent corrosion and freezing L 4 Prevent cavitation and lubricate the pump seal O16 A cooling system thermostat that is seized in the open position will cause Tick one box only LU 1 The viscous coupling on the clutch to lock up LU 2 The engine to overheat U 3 Excessive water pump speeds L 4 Excessive fuel consumption and exhaust emissions Q17 Conduction is the transfer of heat Tick one box only UL
48. ossesecassnsssnssseessenees 24 10 0 Servicing the Cooling System ccsssesssseeseseessseesseeessneeeseeeeeseeeeenees 27 101 Draining amp Refilling Coolant eeeereeeeeeeerseeseesseeesseesseesseeenss 27 11 0 Testing Viscous Coupling and a Bi Metal Switch ieeeeeeeeeseeseeessaes 29 12 0 Cooling System Components and Pressure Test eeeeeeeeeeeseeeeesssaes 29 12 1 Testing Cooling System Pressure scsscsssssscssssnssencsssoesoeses 29 13 0 Overheating or Overcooling ssssssssssssissssrrorssssisvosssiosssssecvcsocesssssesrssvsssas 33 13 1 Causes of Engine Overheating cccssscsssseessrteesereesseeesseeeens 33 Self Assessment sosisini eE ae oE Re E N ERER SA T ER K AS TAS 37 SUS RESIER Exerc GL nann a EA E E Bha ANSA 43 Miranin RESOU Euin ena ea a seeees sstusnetag soeausiseesceselinees 43 Task BIC onien ne e ER I a R 44 Checking amp Adjusting Coolant ccccssssccssseeesseeeeseeeeeneeeeneeeeeseeeenses 44 Draining amp Refilling Coolant ccssscsssseessseesseessencesseeeeseeeeenseeees 47 Checking amp Replacing a Coolant Hose cccccssecesssesesteeeeseeeeseeeenees 49 Testing Cooling System Pressure ss xssssccsstessissssssgeessstsusissanssonnsssdieneasicnss 52 Removing amp Replacing a Radiator cccssscsssseesseteessssessseesseeeeseeeeees 55 Removing amp Replacing a Thermostat ccccssssscsssscesessssesseveeeeneeees 58 Inspecting amp Adjusting an Engine Dri
49. ough high levels of surface water and some of the splashing water is drawn into the air intake A very serious problem for conrods and pistons s Hydraulic lock of the engine during starting Engines with faulty cylinder head gaskets allow combustion gases into the coolant but the reverse will also happen As a faulty head gasket problem persists and the system is being continually topped up with coolant over the longer time period coolant may begin to enter the cylinder when the engine is switched off and eventually if enough gets inside the combustion chamber a hydraulic lock may occur during starting Electrolysis damage A problem that is more often associated with large diesel engines that use wet cylinder liners but the problem of electrolysis attacking and eventually making holes through from the outside to the inside of the wet liner does affect petrol engines that use these wet liners sleeves Holes from electrolysis may be invisible from the cylinder interior and therefore the cause of the overheating may be difficult to diagnose fully Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 34 Module 3 Unit 3 Cooling System Effects of Serious Overheating on Engine Components Cylinder head damage due to overheating The cylinder head will usually suffer distortion damage i e warp should head gasket faults and over heating occur Warp is the term used to describe distortion
50. p Expansion tank Hot water expanding As the engine cools coolant contracts and pressure in the radiator drops Atmospheric pressure in the overflow container opens a second valve and overflow coolant flows back into the radiator 3 10 Temperature Indicators Overheating can seriously damage an engine so having warning of trouble is obviously useful A device that s sensitive to engine temperature sends readings to a temperature gauge or a warning lamp To give an accurate reading this sensor must always be immersed in liquid Temperature gauge Temperature sensor m Coolant a ry Indicators that measure coolant levels can give warning if the level falls too low Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 12 Module 3 Unit 3 Cooling System 3 11 Thermo Switch Bi Metal Switch A thermo switch opens and closes according to pre set temperature levels Some are mechanical others are electrical It may be designed to switch off when temperature rises above a certain level or it can be made to switch on when the temperature reaches a certain level Heat switches can operate on the bimetallic strip principle It consists of two different metals or alloys attached back to back As different metals and alloys heat and cool they expand and contract differently That means that if they are joined and then heated the faster expansion of one will force the whole strip into a curved sha
51. pe Contact points As the strip changes shape it can be designed to complete a circuit and a resulting electrical signal can then do a range of tasks or it might have a mechanical effect simply opening a passageway Cooling then produces the opposite effect Breaking the circuit and closing the passage Testing of this type of switch can only dome using manufactures specifications Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 13 Module 3 Unit 3 Cooling System 3 12 Water Pump The water pump is usually in front of the cylinder block belt driven from a pulley on the front of the crankshaft A hose connects it to the bottom of the radiator where the cooler liquid emerges It has fan like blades on a rotor or impeller Coolant enters the centre of the pump The rotor spins and centrifugal force moves the liquid outward It is driven through the outlet into the cooling passages called waterjackets 3 13 Centrifugal Force Centrifugal force is a force pulling outward on a rotating body A vehicle turning a curve is a similar system to this rotating body so it is subject to centrifugal force too Centrifugal force resists turning and tries to keep the vehicle moving in a straight line Centrifugal force is also the force that causes an out of balance wheel to vibrate Centrifugal force can also be useful When coolant enters the centre of this pump and the rotor spins centrifugal force moves the l
52. r and damage You may need a flashlight to see these clearly A cracked or glazed or torn belt will need to be replaced Check tension Check the belt tension by attaching the tension gauge to the longest belt span and pulling it to measure the tension Compare your reading to the specifications in the vehicle workshop manual Choose the correct tools Select the correct wrench to loosen the tension adjustment fastener This is usually on the Alternator mounting or on a separate idler pulley wheel You will also need a pry bar which is a metal bar you can use as a lever to apply tension on the belt Adjust belt tension Loosen the adjustment fastener then wedge the pry bar between the alternator and a strong part of the engine and pull in the direction that will apply tension to the belt Tighten the adjustment fastener Check tension again and readjust if necessary Check the tension again with the gauge and if necessary loosen the fastener and adjust the belt again until it is at the correct tension for the vehicle Start the engine Start the engine and observe the belt to make sure it is properly seated and operating correctly Stop the engine again and recheck the tension Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 64 Module 3 Unit 3 Cooling System Suggested Further Reading Advanced Automotive Diagnosis Tom Denton ISBN 0340741236 Automobile Electrical and Electronic Systems 3rd Ed
53. replaced immediately Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 62 Module 3 Unit 3 Cooling System Bottoming out When a V type belt becomes worn the bottom of the V shape may contact the bottom of the groove in the pulley preventing the sides of the belt from making good contact with the sides of the pulley groove This reduced friction causes slippage a belt worn enough to bottom out should be replaced Bottomed out Manual Belt Tension Versus Automatic Belt Tension Many vehicles require the technician to manually adjust the tension on the belt Other vehicles have an automatic spring tensioning system Depending on the system used on the particular vehicle you should always follow the manufacturer s service instructions There are a number of different types of tension gauges Follow the operating instructions on the tool If you don t have a tension gauge you can estimate the tension by pushing the belt inwards with your hand If it s correctly tensioned you should be able to deflect the belt about 1 25 centimetres for each 30cm of belt half an inch for each foot Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 63 Module 3 Unit 3 Cooling System Step by Step Instruction 1 Inspect and check belt condition Twist the belt so that you can see the underside of the V shape or the ribs on a Serpentine belt Look for signs of wea
54. should be at the lower mark when the vehicle is cold The coolant level should be at the upper mark when the coolant is hot If the reservoir is completely empty add coolant until the level is up to the appropriate mark for the engine temperature Then run the engine until it is at its normal operating temperature and check the level again You will probably need to adjust the level again Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 45 Module 3 Unit 3 Cooling System For each 10 kPa increase in the radiator cap operating pressure it will increase the boiling point of the coolant by 2 C 1 PSI for each 3 F Step by step Instruction 1 Check fluid level Most modern vehicles have a coolant system that uses a transparent recovery tank as a coolant reservoir Check the level of coolant in this reservoir if the engine is hot the level should be visible at the upper mark If the engine is cold it should be at the lower mark Check protection level with a hydrometer Before adding new coolant check the specific gravity of the coolant in the system with a coolant hydrometer Draw some coolant up into the hydrometer and read the mark on the float at the level of the fluid in the chamber This will indicate the freezing point of the coolant mixture in the system so you can tell if it has the right proportions of antifreeze and water Adjust fluid level Check the service manual for the rec
55. tes SOLAS An tSeirbh s Oideachais Lean naigh agus Scileanna Further Education and Training Authority 27 33 Upper Baggot Street Dublin 4
56. this unit each apprentice will be able to Describe the function and operating principle of a sealed liquid cooling system for a multicylinder automobile engine Describe the basic operation of a mechanically driven fan forced air engine cooling system Define the following terms heat transfer conduction convection and radiation Define the following terms temperature Celsius scale Kelvin scale Test the operation of the principal cooling system components Describe the effects of ambient pressure levels on the boiling point of water Describe the hazards involved and Health and Safety precautions applicable when working on cooling systems Describe the advantage and disadvantage features of liquid and air cooling systems Use an antifreeze hydrometer to test the strength of antifreeze solution in a cooling system Describe the end of useful life procedures to be used with engine coolant Drain a cooling system fit antifreeze bleed and top up the system Check the operation of the viscous coupling and bi metal switch type automatic cooling fans Change cooling system components and pressure test the system for leaks Describe the main causes and resultant effects on engine components and performance by overheating or overcooling Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 Module 3 Unit 3 Cooling System 1 0 Hazards and Safety Precautions 1 1 Health and Safety If the
57. tion such as earmuffs and earplugs Hand protection such as rubber gloves and barrier cream Respiratory equipment such as face masks etc Coolant in the cooling system could be above its boiling point Never open a radiator cap fully until ALL pressure has been released Before removing the pressure cap check the temperature of the cooling system with an infrared temperature gun if you have one available When removing a radiator cap use appropriate gloves clothes full face shield etc Before commencing a repair or service task on the cooling system and allow approximately 30 minutes for the system to cool sufficiently before opening the pressurised system When removing a radiator cap use appropriate gloves clothes full face shield etc Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 58 Module 3 Unit 3 Points to Note Cooling System Make sure that you understand and observe all legislative and personal safety procedures when carrying out the following tasks If you are unsure of what these are ask your instructor Drain the at least 50 of the coolant in the system to avoid spills Position the thermostat air bleed valve if fitted in the proper position Make sure the thermostat is fully seated in the groove and stays there before fitting the housing Failure to do so will damage the new thermostat and possibly break the housing as it is tightened up Tighten the ho
58. to very weak and may collapse and leak close up completely Clamp Types Gear or worm type clamp Banded or screw type clamp Adjust with a screwdriver Also adjusted with a screwdriver Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 Module 3 Unit 3 Cooling System Wire clamp This spring clamp is not adjustable and is fitted and removed with special hose clamp pliers which have grooved jaws Clamps are not expensive so it is good practice to fit new ones at the same time as new hoses Even if not corroded the old clamps may have become distorted when being removed from an unserviceable hose Step by Step Instruction 1 Inspect hoses and clamps Locate both the hoses that carry coolant between the radiator and the engine One is at the top and the other is at the bottom of the radiator Squeeze each hose It should feel pliable and springy If it feels very soft and weak ot very hard and brittle it will need to be replaced Look for signs of swelling or cracking particularly on the vulnerable underside of the lower hose Check that the clamps are holding the hoses firmly in position and are not corroded 2 Remove hose Drain the coolant from the system before removing either of the hoses Remove the clamp using the appropriate tool If the hose is stuck and won t pull off easily be careful you do not damage the radiator fitting by using too much force It is better to cut the hose in several
59. ubber gloves and barrier cream Respiratory equipment such as face masks etc Safety Check e Always be very careful when opening a radiator cap because the cap keeps the coolant under pressure to raise its boiling point Sometimes even the pressure in a warm engine can force the coolant to spurt out when the cap is released Always cover the radiator cap with a rag to catch any hot spray Always wear eye protection Never open a radiator cap on an overheated engine wait for it to cool down first Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 44 Module 3 Unit 3 Points to Note Cooling System Always make sure that you wear the appropriate personal protection equipment before starting the job It is very easy to hurt yourself even when the most exhaustive protection measures are taken Always make sure that your work area environment is as safe as you can make it Do not use damaged broken or worn out workshop equipment Always follow any manufacturer s personal safety instructions to prevent damage to the vehicle you are servicing Make sure that you understand and observe all legislative and personal safety procedures when carrying out the following tasks If you are unsure of what these are ask your instructor There ate two correct level marks on the reservoir because the coolant in the system expands and contracts in volume depending on how hot it is The coolant level
60. uld be above its boiling point Never open a radiator cap fully until ALL pressure has been released When removing a radiator cap use appropriate gloves clothes full face shield etc Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 55 Module 3 Unit 3 Points to Note Cooling System Make sure that you understand and observe all legislative and personal safety procedures when carrying out the following tasks If you are unsure of what these are ask your instructor Make sure the coolant catch tray is large enough to catch any spills and has the capacity to hold all the system coolant If changing coolant dispose of the old coolant properly in accordance with environmental and legislative requirements If reusing the old fluid keep it stored in a covered and uncontaminated container Inspect the cooling system hoses and clamps Replace them if worn or damaged When removing the hoses from the radiator fittings do NOT twist them as this can cause internal damage to the hose and the fitting If they do not easily release carefully work a tool between the hose and fitting breaking it loose all the way around If the hoses are to be replaced you can slit them with a knife and peel them off the fitting When refitting or replacing hoses reinstall them all the way on the fittings Make sure the clamps are installed at the proper place on the fitting beyond the flared segment not on top of it
61. umber of different analyzers used today Make sure you are familiar with the system used in your workshop Pressure AN bhuil G If you need to replace a pressure cap use only a cap with the correct recommended pressure If a cap with a lower pressure rating is fitted it will lower the boiling point of the coolant Alternatively a higher rated cap will increase the boiling point Max operating pressure 120kPa Each 10 kPa 1 45 PSI of cap rated pressure changes the boiling point by 2 C For example A 90 kPa 13 PSI radiator cap will increase the boiling point from 100 C to 118 C Similarly a 100 kPa 14 5 PSI radiator cap will raise the boiling point from 100 C to 120 C Pressure testing kits come with a number of adapters for various cooling systems These adapters can be used to connect the tester to the radiator or to the radiator cap Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 31 Module 3 Unit 3 Cooling System Step by step Instruction 1 Inspect cooling system visually Before pressure testing the system visually inspect the system for any obvious signs of leaks or wear in the radiator core radiator tanks coolant and heater hoses water pump all accessible engine core plugs cooling fan drive belt and radiator cap and seals Check the operating instructions of the tester Refer to the pressure tester s manual for correct operation The outside of the r
62. ure the engine is off when carrying out any visual inspection of the system or when you connect the tester You may be required to run the engine after the tester has been installed and pressurized When the engine is running make sure that you keep any loose clothing away from rotating parts When pressure testing a system make sure you do not exceed the manufacturer s maximum pressure Have a qualified instructor show you the correct operation of the tester Make sure that you understand and comply with all environmental and occupational health and safety standards for your workplace at all times If you are unsure of what these are ask your instructor To test the cooling system for both internal and external leaks a pressure tester is normally used These are often referred to as cooling system testers or analyzers There are a number of different analyzers used today Make sure you are familiar with the system used in your workshop Pressure pump Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 53 Module 3 Unit 3 Cooling System If you need to replace a pressure cap use only a cap with the correct recommended pressure If a cap with a lower pressure rating is fitted it will lower the boiling point of the coolant Alternatively a higher rated cap will increase the boiling point Max operating pressure 120kPa Each 10 kPa 1 45 PSI of cap rated pressure changes the
63. us C scale was devised by dividing the range of temperature between the freezing and boiling temperatures of pure water at standard atmospheric conditions sea level pressure into 100 equal parts Temperatures on this scale were at one time known as degrees centigrade The kein K temperature scale is an extension of the degree Celsius scale down to absolute zero a theoretical temperature characterized by a complete absence of heat energy Temperatures on this scale are called kelvins NOT degrees kelvin Kelvin is not capitalized and the symbol capital K stands alone with no degree symbol Temperature Relvin K Degree Celsins C Boiling point of water 100 Melting point of ice 0 Absolute zero 273 15 Temperature Conversions Between the Three Temperature Scales Kelvin degree Celsius Conversions exact kelvin degree Celsius 273 15 degree Celsius kelvin 273 15 Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 Module 3 Unit 3 Practical Task Objective Personal Safety Safety Check Cooling System 6 0 Testing Cooling System Components Please refer to your instructor for additional information which is available from the automotive technical manuals 6 1 Removing amp Replacing a Thermostat Preparation and Safety Safely remove and replace a cooling system thermostat Whenever you perform a task in the workshop you must use personal protective clothing a
64. using bolts to the correct torque Make sure to use the manufacturer s procedure to properly bleed all air from the cooling system Step by Step Instruction I Remove the thermostat Unbolt the thermostat housing from the engine block Be very careful not to damage the housing as it is generally made from aluminium or a similar fragile material Remove the thermostat Inspect the mating surfaces Inspect the thermostat housing and remove any gasket material from the mating surface of the housing Inspect the engine block and remove any gasket material from its mating surface Install the new thermostat Inspect the new thermostat to ensure that the identification number is the same as the one you have removed Fit the new thermostat ensuring the air bleed hole is in the correct position Check the thermostat is fully seated in its groove Fit the correct type of gasket for the vehicle you are working on Carefully refit the thermostat housing to the engine block and bolt it into place Refill the cooling system Refill the system with coolant Run the engine to circulate the coolant and remove any air trapped in the system Check that the temperature indicator gauge shows the coolant temperature is in the normal operational range Top up the radiator or reservoir with coolant if necessary Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 59 Module 3 Unit 3 Cooling System Inspecting amp Adjust
65. ve Belt ieeeeeeeeeeeneesneeeeeease 60 Suggested Further REAGiiS lt cccsscsssssseccsssseesesvessecsesavssvessisesescosavssssessossecansneses 65 Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 Module 3 Unit 3 Cooling System Introduction This unit covers the basic function and operation of the cooling and system of the automotive internal combustion engine Combustion of the air fuel mixture in the cylinders generates heat which produces high pressure to force the piston down in the power stroke Not all of this heat can be converted into useful work on the piston and it must be removed to prevent seizure of moving parts This is the role of the cooling system There are two types of cooling systems liquid cooled and air cooled Liquid cooled being the most common In modern cars the engines that are liquid cooled a water pump forces the liquid through passages called water jackets in the engine block It collects heat by conduction and becomes hot itself Heated coolant then returns to the radiator for cooling and the cycle is repeated Heat is removed from the engine and dispersed thus preventing overheating These components along with the air cooled components and it s related health and safety issues will be covered in detail within this unit Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 Module 3 Unit 3 Cooling System Unit Objective By the end of
66. ze Boiling coolant in the water jacket becomes a vapour No liquid is left in contact with the cylinder walls or head Heat transfer by conduction stops Heat builds up and that can cause serious damage One way to prevent this is with a radiator pressure cap that uses pressure to change the temperature at which water boils As coolant temperature rises the coolant expands and pressure in the radiator rises and that lifts the boiling point of the water Engine temperature keeps rising and the coolant expands further Pressure builds against a spring loaded valve in the radiator cap until at a preset pressure the valve opens In a recovery system the hot coolant flows out into an overflow container As the engine cools coolant contracts and pressure in the radiator drops Atmospheric pressure in the overflow container then opens a second valve a vacuum vent valve and overflow coolant flows back into the radiator This system stops low pressure developing in the radiator and that stops atmospheric pressure collapsing the radiator hoses Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 11 Module 3 Unit 3 Cooling System 3 9 Recovery System A recovery system maintains coolant in the system at all times As engine temperature rises coolant expands Pressure builds against a valve in the radiator cap until at a preset pressure the valve opens Hot coolant flows out into an overflow container Radiator ca

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