Introduction to Timing Belts and Systems
Contents
1. Timing Belts 101 GATES Progesional Development ISERIES INTRODUCTION TO TIMING BELTS AND SYSTEMS 1019 Table of Contents Introduction t O Ti m N g Timing System OVErVIEW iana Page 2 Belts and _ a Sys te m S EINES ee g System ComponentS 2 uu202000000n0nannnnnnannunnnunnannnnununnnnannnn ann Page 6 BES REED EEE EEE Page 8 Failure MOG iz EEE nen Page 13 Timing Belt Troubleshooting 2 2 u20200000a0annana0nunanannannunn Page 17 PowerGrip Timing Tensioner Kits uu020 002000nana0nnnannnnannnnnn Page 19 INTRODUCTION TO TIMING BELTS Timing System Overview Why a Synchronous Belt in Automotive Engines Synchronous belt drive systems used to synchronize cam and crank Shafts replaced the classical chain drives when overhead camshafts were introduced into engine technology in the 1970s Automatic Tensioner sacks Micro V Air Conditioning Belt amp V Belts Pulley Zu idler Pulleys AND SYSTEMS 101 A timing belt is a flat toothed rubber belf that synchronizes an engine s valve and piston movement The first belt was made of polyurethane with steel cord tension members During ongoing developments polyurethane was replaced by very strong and temperature resistant rubber materials In addition the tension member was changed to fiber glass which provided excellent flex and very low elongation behavior During further engine developments Suppor2. m Efficiency A belt drive system can reduce up to 4 5 horsepower in friction loss Less Vibration e A chain drive system shows lower transmission error A belt drive system can be optimized to be equal or better than chain m Reduced Noise Creep Wear e Current belt technology provides less than 0 1 percent total length change Durability Capability e Similar applications with belt drive systems are proven in the industry m Package A belt drive system fits within the chain drive package Weight A belt drive system can save approximately 1 5 kg 3 3 lbs per engine Cost e Overall costs of implementing a belt drive system are generally lower than chain Complexity Timing System Overview A belt drive system uses less components and part numbers INTRODUCTION TO TIMING BELTS Engines Design Overhead cam OHC engines come in two types single overhead cam SOHC or dual overhead cam DOHC These cams are driven by the crankshaft by the use of a timing chain or a timing belt There are lobes on the camshaft s that cause the exhaust and intake valves to open or close These lobes contact the valves directly or by the use of cam followers Despite their many differences one thing all overhead cam engines share in common is a need for good upper valvetrain lubrication OHC timing belts can snap unexpectedly at high mileage Heat and friction weaken the cords that reinforce the belt The risk of f
3. contact if the belt fails Interference engines usually sustain damage if synchronization is lost As illustrated disrupted synchronization allows the piston and valve to collide causing damage and very expensive repairs for the vehicle owner Damage can occur to valves pistons or heads and in some cases completely ruin the engine Most import with higher compression engines and car and light truck diesel engines are interference To avoid costly engine repairs follow the auto manufacturers mileage replacement recommendations Free Running Interference No Valve Piston Interference Valve Piston Interference Balance Shaft versus Camshaft 4 Cylinder Engines Four cylinder engines are attractive to vehicle designers because of their short compact configuration This allows them to be fitted transversely into the engine compartment which frees up more space for passengers and cargo In addition short crankshafts and compact cylinder blocks save performance robbing weight However when 4 cylinder engines grow larger than about two liters in displacement the second order vibration twice per engine revolution set up by their pistons and connecting rods can become obnoxious The balance system consists of two parallel shafts on either side of the crankshaft Driven by a toothed belt the balance shafts rotate in Opposite directions at twice engine speed Eccentric weights built into the shafts generate inertial forces that c
4. teeth resulting in early failure by shearing teeth off the belt It is recommended that the belt tension be checked by a proper tool such as Gates Timing Belt Tension Tester Part No 91000 once tensioners are installed Tension springs are not included in Gates Timing Component Kits Warranty Returns At Gates we do everything possible to prevent timing belt returns We provide the right belt for the application and offer instructions tools and system components to help ensure the job is done right Timing belts are returned because the engine failed prior to the next scheduled maintenance interval In most cases the timing belt takes the blame for other engine component failure If a belt is returned some simple checks can determine the cause of failure Typical returns can be traced back as being caused by 1 Using the incorrect belt for the application The Timing belt 2 Improper installation drive must be looked at as a system and If Is crucial that every component in the system be prop erly maintained 3 Other component failure 4 Technical Service Bulletins TSBs not followed or known about 5 Timing components used beyond their recommended life Failure Modes INTRODUCTION TO TIMING BELTS AND SYSTEMS 10 1 Determining if the correct belt for the application was used may sound simple but sometimes little things can be overlooked For example There are some aftermarket timing belts that are
5. the same length but are intended to be used on completely different applications An older engine may have only required a Neoprene belt while the newer engine required an HSN belt and the installer tried to save some money and installed the wrong belt An older engine was replaced with a newer one and the customer was given a belt based on the year of the car and not the year of the engine After checking that the belt is correct for the engine a look at the belt can help point to the root cause Refer to the Troubleshooting Guide on page 23 of this training guide or Gates PowerGrip Timing Belt Replacement Manual for examples of failed belts and possible causes and solutions To properly determine what caused failure all the system components SE must be reviewed If only the belt was replaced initially then another Installing d timing component is probably at fault All moving components in the drive belt af higher tha n are subject to wear and need to be replaced at recommended intervals or sooner recommended gt For instance it is highly recommended on systems that include a water fensioners drastically Doi gt pump in the drive that the water pump be replaced at the same time as reduces the life of the timing belt Bearings in water pumps idlers and tensioner pulleys are the bea rings ASen to Zul operating conditions and nee to pe Dacen 1 a belt was installed at higher than recommended tensions this will drasti
6. the timing belt is engineered for that particular engine Each timing belt part number offered by Gates represents a timing belt designed to work for a specific engine One belt cannot fit multiple engines A different Gates part number indicates the belt is unique and is different than all the other part numbers The aftermarket timing belt must be as good as or better than the OEM timing belt When a new part number is released by Gates we match the OEM belt for fit form and function The Gates aftermarket timing belt is thoroughly researched so that it matches the OEM for Tooth profile Physical dimensions length width etc Materials Timing marks Manufacturing requirements All these attributes are very important and since Gates is the leader in the supply of timing belts to the OEM we are able to offer the same belt in the aftermarket Physical Dimensions The dimensions of the timing belt are very important and must be closely maintained in order to function on the engine A belt that is too long or short will not allow the tensioning device to operate in the intended range for which it was designed This will result in excessive noise or even premature failure Gates timing belts are manufactured with strict adherence to tolerances for all physical attributes INTRODUCTION TO TIMING BELTS AND SYSTEMS 101 Materials The three main rubber compound designations that Gates uses to identify timi
7. ailure goes up sharply after about 60 000 klim on most OHC engines built before the mid 1990s This is why Gates along with most vehicle manufacturers recommends replacing OHC timing belts for preventative maintenance at 60 000 klm intervals Starting in the mid 1990s OHC timing belts made of more durable materials began to appear with 90 000 to 100 000 klm replacement intervals These new long life belts which are made of a special high temperature grade of rubber called highly saturated nitrile HSN were first introduced by Gates HSN extends belt life up to 50 percent or more and reduces the need for periodic belt replacement AND SYSTEMS 101 Gates was the first to introduce timing belts made of highly Saturated nitrile HSN a special high temperature grade of rubber Engines INTRODUCTION Gates Timimg Belt and Timing Tensioner Kit Wall Chart part no 496 204 makes finding interference easy TO TIMING BELTS AND SYSTEMS 101 Free Running or Interference Automobile engines can be classified as either free running or interference depending on what occurs if piston valve synchronization is lost As illustrated to the right in the free running engine with the crankshaft still moving there is enough clearance between the valve and piston even if the cam stops with a valve fully open However with interference engines there is not enough clearance between the valves and pistons to prevent
8. cally reduce the life of the bearings A quick review of the installation instructions can sometimes point out pit falls an installer may have encountered The mechanic needs to follow all the instructions and follow up with an operational check to make sure the system is functioning properly This is the last opportunity for the mechanic to make corrections before the next belt change After installation is complete be sure to run the engine and check for noise vibrations and engine performance Failure Modes INTRODUCTION TO TIMING BELTS Manufacturing Defects Gates manufacturing facilities have implemented several quality control processes and procedures to virtually eliminate defects in manufacturing The only thing the customer needs to make sure of is that the Gates belt is the same as the belt they are replacing Things to look for include 1 Belt dimensions length and width 2 Tooth shape correct for sprockets 3 Timing marks 4 Directional arrows these are used to make sure the belt is running in the proper direction of rotation for the belt timing marks to line up with the engine marks Proper Handling of Timing Belts Synchronous belts have been used on automotive camshaft drives for more than 20 years Gates belts will give OEM equivalent service if the following points are observed Do not allow timing belts to be crimped If the tensile members in a timing belt are bent then the strength is
9. cing all wear items in the system each time a belt is replaced is also a good idea Since a large part of the repair bill is the labor involved in changing a timing belt it makes sense to replace all the components at the same time For the majority of engines Gates offers all the components in the timing belt drive such as Timing belt Idler s Tensioner The most likely scenario for a prematurely Stripped timing belf is one in which the engine has been run low on oll Water pump Seals Installation instructions Checking the Belt Determining the true condition of a timing belt is not easy for two reasons 5 1 Most timing belts are hidden beneath covers that must first be removed to inspect the belt 2 A simple visual inspection won t necessarily tell you if a belt is good or bad Some belts that look like new on the outside are dangerously weak on the inside and may fail without warning Failure Modes INTRODUCTION TO TIMING BELTS AND SYSTEMS 101 Belt Tensioning Proper tensioning of timing belts is very critical High belt tensions can result in excessive noise such as a whining sound early bearing failure due to the increased loading of the bearing by the belt damage to the land area of the belt leading to tooth cracks and or tensile member failure Low belt tensions can lead to the belt flapping and possibly hitting the covers put higher stress on the belt
10. drastically reduced and the belt will fail prematurely Do not use any solvents to clean a timing belt Always replace belts that have been contaminated with engine fluids such as oil grease and anti freeze These substances can break down the rubber compounds and destroy the glue that holds the different parts of the belt together Do not rub the sides of the belt twist the belt excessively or use tools to pry the belt onto the drive Tools will damage the belt and create weak points that can lead to premature failure Always store belts in the original box and do not stack heavy objects on the belts as this will twist or kink the belt Store belts in an environment that avoids e Temperature extremes e Direct sunlight e High humidity e Contamination by oil water chemicals etc Replace and properly refit the timing cover to prevent drive contamination by foreign matter AND SYSTEMS 10 1 Always store belts in the oroginal box fo avoid damage and premature failure Failure Modes INTRODUCTION TO TIMING BELTS AND SYSTEMS 1019 Timing Belt Troubleshooting Failure Modes Symptom Probable Cause Concern Corrective Action Tensile Excessive shock load 1 Excessive RPMs Failure modified engine Improper belt handling 2 Follow proper and storage prior to storage and installation handling procedures Debris or foreign 3 Remove objects object in drive replace pulleys Extrem
11. e pulley 4 Replace pulley sprocket run out sprocket Extreme over tension 5 Adjust tension to recommended value Tooth Seized drive 1 Replace component s Shear component s tensioner idler pulley water pump camshaft oil pump Excessive shock loads 2 Excessive RPMs modified engine Extreme sprocket 3 Check camshaft run out crankshaft journals Worn sprocket 4 Replace sprocket Misaligned drive 5 Worn sprocket bearing replace sprocket bent bracket improper sprocket installation Belt under tensioned 6 Adjust tension to recommended value Tooth Wear Too low or high 1 Adjust tension to belt tension Belt running partly off unflanged sprocket Misaligned drive Worn sprocket recommended value 2 Correct alignment 3 Worn sprocket bearing replace sprocket bent bracket improper sprocket installation 4 Replace sprocket INTRODUCTION TO TIMING BELTS AND SYSTEMS 101 Symptom Probable Cause Concern Corrective Action Backside 1 Extreme high 1 Overheated engine Cracks temperature seized or partially seized pulley Extreme low Install engine heater temperature at start up E Cocked sprocket Replace sprocket Excessive tension Adjust tension to recommended value Land Wear Excessive tension Adjust tension to wear between teeth Contamin ation Edge Wear Unusual Noise not shown Worn sprocket Oil fuel or coo
12. eplaced 2 Did you buy the car used If so they won t know if the belt has been replaced This is a flag for the customer to get the belt checked replaced or at least be aware that they have a timing belt 3 How many miles are on the vehicle Generally belts should be replaced at around 100 000 kims or less Gates Timing Belt Replacement Mileage Wall Chart Product No 428 0408 is an excellent tool for determining replacement intervals 4 Have you ever replaced the timing belt If the answer is yes or no and the customer knows the mileage you can determine where the vehicle is in the replacement cycle SYSTEMS 10 1 A timing belt system inspection should be performed with any other under hood service onan engine with 50 000 klms or more INTRODUCTION TO TIMING BELTS AND SYSTEMS 101 Comparing OEM and Aftermarket Belts Timing belt applications have increased dramatically There are now more than 700 models of Australian and foreign made cars and light duty trucks with overhead cam engines using timing belts This dramatic number of timing belt applications is the result of auto makers satisfying motorist s demands for spirited responsive vehicles powered by efficient multi valve engines Gates timing belts are designed to handle the wide speed range and constant synchronous drive power requirements common with these engines When an engine is prepared for introduction into the market place
13. er from the engine place it between vice jaws and slowly compress the piston Once compressed line up the holes in the piston with the holes in the cylinder and insert a pin to hold the piston in place The Gates Pin Set is the only tool created just for this purpose Part No 91010 Hydraulic Damper Pivot Arm NOTE Proper tensioning of timing belts is very critical Please refer to page 18 of this guide for more information System Components INTRODUCTION TO TIMING BELTS Belts Tooth Profiles The earliest timing belts had a trapezoidal tooth profile Competition and more demanding applications led to the development of a curvilinear profile This in turn evolved into a modified curvilinear profile Belts with different tooth profiles are not interchangeable Gates has the most complete timing belt line available with more than 450 part numbers The line includes both neoprene and HSN highly saturated nitrile constructions and all three tooth profile types Trapezoidal h m ae Curvilinear Tv Modified Curvilinear wee Neoprene was standard until 1985 when Gates introduced the first belts made of HSN In short supply and difficult to engineer HSN was the material of choice for most new timing belts An HSN constructed belt appears no different than a neoprene belt but significantly outperforms in the high temperature engine compartments of modern vehicles In 2000 OEMs began using upgraded materials in timin
14. g belts and Gates followed on aftermarket belts While the name remained the same this newer HSN is higher grade on all drives requiring an upgrade Rubber was not the only improvement made to timing belts the cord and jacket material were upgraded as well Construction Materials Today s timing belts are highly sophisticated The days of generic timing belts made of standard materials and tooth profiles are gone Improved new generation belts are providing the extended durability and smoother performance characteristics required by today s engines Gates leads the world in timing belt technology assuring customers a replacement belt to match the capabilities of the original belts SYSTEMS 10 1 There are several different tooth shapes used by Gates and other timing belt sup pliers Some look very similar to one another but are different enough to drastically reduce the life of the timing belt if the wrong tooth shape is used Belts INTRODUCTION TO TIMING BELTS AND SYSTEMS 10 1 High Strength Tensile Cord HNBR Elastometric Compound Improved Tooth Jacket HNBR or HSN Elastomeric Compound Forms the main body of the belt While it is impor Formulated for better heat resistance and durability tant To inspect m Wide temperature range 40 C to 140 C belts whenever a Crack resistant vehicle comes in for service it s not always possible to tell if a belt is High flexibility st
15. ill good by visual Heat resistant inspection alone Fatigue resistant High Strength Tensile Cord Designed for high tension applications Normally S and Z twisted to prevent tracking Low creep or zero stretch Improved Tooth Jacket Engineered for improved wear resistance Abrasion resistant Heat resistant Fatigue resistant Expected Belt Life Today s belts operate under heavier loads and are exposed to many factors that may cause premature failure including heat and temperature fluctuations water dirt grease oil and other environmental contaminants In addition hotter smaller engine compartments put more stress on belts and components Idling time in traffic also takes a major toll on belt life The engine runs hotter and belts can break down much more rapidly in a car exposed to sustained periods of stop and go driving Sometimes the first indication of a faulty belt is a squeaking noise coming from the engine compartment While a warning of a possible malfunction this noise is not a precise indicator Therefore it is imperative to inspect belts whenever a vehicle comes in for service If there is ever any doubt recommend replacement of the belts The alternative could be a customer stranded in the middle of rush hour with a broken belt and a disabled vehicle INTRODUCTION TO TIMING BELTS AND OEM Recommended Replacement Intervals Whether your customer s vehicle utilizes a free run
16. lant leak Damage due to handling Flange damage Belt tension too low Rough belt pulley flange Improper tracking Belt contacting engine timing cover or other engine component High tension Low tension Misalignment Damaged pulley flange Replace sprocket recommended value I Replace sprocket Replace faulty seals and or gaskets check timing cover for improper installation replace if cracked or worn Follow proper handling instructions Replace sprocket Adjust tension to recommended value Correct alignment Remove obstruction or correct alignment Adjust tension to recommended value Adjust tension to recommended value Worn sprocket bearing replace sprocket bent bracket improper sprocket installation Replace pulley s Failure Modes INTRODUCTION TO TIMING BELTS AND SYSTEMS 10 1 PowerGrip Timing Tensinoer Kit Gates PowerGrip Timing Tensioner Kit gives you the best and most complete repair solution for your customers Save time and money by preventing costly comebacks and warranties The Kit is ideal for the consumer because the job is done right the first time saving them from returning when other components fail and accruing additional labor costs With Gates PowerGrip kits it s not necessary to multi source components look up several different manufacturers or present you
17. ng belts are 1 Neoprene for older easy running engines 2 High Temperature Neoprene which was an improvement over neoprene belts for heat resistance and 3 HSN which includes several different material combinations over the first two material options Not all HSN belts are alike In addition to different rubber compounds timing belt materials are made with different tensile members and belt jacket materials The Gates aftermarket belt will match the look and feel of the OEM timing belt exactly Timing Marks Engine manufacturers will sometimes apply timing marks on the timing belt to assist in the installation of the belt These marks are to ensure that the camshaft s is are in time with the crankshafts If the timing marks do not line up properly this is a warning to the installer that something isn t set up right Gates makes sure that these marks are located properly on the belt to remove the guesswork when installing timing belts Timing marks can be found on all relevant Gates aftermarket timing belts that require Specific markeings INTRODUCTION TO TIMING BELTS AND SYSTEMS 1019 Failure Modes Replacement Always follow the vehicle manufacturer s instructions regarding belt replacement intervals If the belt is removed then a new belt should be installed If the engine is being repaired and the belt is near OEM recommended replacement interval its a good time to replace it Repla
18. ning or interference engine timing belt failures can be avoided by adhering to the OEM recommended replacement intervals and preventative maintenance Most OEM quality belts can be expected to last at least 100 000 klms as long as there are no problems found with the other components that may cause premature system failure Also severe conditions such as towing aggressive driving and maintenance history need to be considered Be aware that some manufacturers do recommend inspecting the timing belt without specifying a replacement interval Gates does not advise this as many timing belts that have failed or are about to fail may look as new as the day they were installed Even if the belt doesn t look cracked worn or oil contaminated it should be replaced at a reasonable mileage interval Gates PowerGrip Timing Belt Manual contains a timing belt replacement interval chart by application NOTE A timing belt should be replaced regardless of mileage if it has become contaminated with engine oil or if it shows signs of premature cracking shredding or general wear Customer Timing Belt Q amp A Since timing belts are inside the engine they tend to be an out of sight out of mind item and are seldom thought of as a part of routine maintenance Here are some questions to ask customers that will help sell belts and protect the customer from expensive repairs 1 Did you buy the car new If yes they ll know if the belt has ever been r
19. ounteract the second order forces INTRODUCTION TO TIMING BELTS AND System Components Timing System Component Identification Engine timing systems utilize one or more of following components idler or pulley tensioner hydraulic damper pivot arm and water pump Tensioners and idlers are important components that work hand in hand with the timing belt If there is damage to a timing belt Gates recommends that these parts be changed as well Belt damage can occur from Too much or too little tension Vibration High temperature Belt misalignment When replacing any timing component including tensioners always refer to the vehicle s service manual After installation always take a few extra minutes to look over all the components and check for proper operation Make sure the pulleys rotate freely check the belt tension and make sure bolts are tightened to the recommended torque values Idlers and Pulleys The timing belt system uses idlers and or pulleys to either change the direction of the belt or transmit power to a component such as a water pump or oil pump Pulleys and idlers are either Smooth located on the back side of the belt and typically used to change the direction of the belt to provide more wrap or teeth in mesh on a sprocket They are also used to break up long spans to prevent belt flutter Notched also called sprockets are located on the tooth side of the belt and exactly match
20. r customer with several cartons containing different parts One carton includes all the components required to do a thorough job Kits can contain multiple belts tensioners idler and tensioner pulleys depending on the application Kit lag Tens gt iming a Ti SSS eee a ee mr E a Timing Tensioner Kits
21. see Service Manual for SS A torque specifications Automatic Spring Loaded Tensioner Also known as a frictional tensioner manufacturers Gates offe rsan are increasing their usage each year of the automatic re spring loaded tensioner because it provides a more easy to use Timing consistent belt tension that can react and adjust Belt Tension Tester to today s high rewing engines Gates carries an extensive line of these tensioners many of which were Part No 91000 RR only available through the OEM until now This fester utilizes Proper installation of these tensioners is critical and installation d compact design instructions must be followed Once installed belt installation is generally measures timing YEDE pe In most en a re wrench is u to rotate the tensioner into a position that permits the belt to slip into place Once the belts up to 30mm belt is in place the tensioner is allowed to return to its operating position wide and costs applying the necessary tension much less than more complicated j Several engine manufacturers Tensioner testers use a pivot arm in correlation with a hydraulic damper to tension the belt This damper uses a piston that pushes a pivot arm with a pulley providing the required tension When re using the hydraulic damper the piston will need to be driven back into its cylinder and locked in place A vice can be used to retract the piston Simply remove the damp
22. ted by the trend to overhead camshafts synchronous toothed belt drive systems became more common in engines This trend was also supported by the many advantages of toothed belt drives including More simple drives Flexible belt routing Lower cost Low elongation behavior and friction losses Constant timing over engine life Lower fuel consumption Less emissions Timing System Overview INTRODUCTION TO TIMING BELTS AND SYSTEMS 10 1 Timing System Operation In an engine the crankshaft drives the camshaft s and actuates the valves via a belt or a chain The timing belt is widely used by car manufacturers because of its advantages over chain namely reduced space as well as lighter and quieter running Today one out of every five passenger cars and light trucks use a timing belt to transmit power from the crankshaft to the camshaft s Most 4 cylinder and V 6 If the belt tensioner engines as well as a few V 8s use a timing belt The timing belt is critical to the pulley and idler engine because it sets the engine s intake and exhaust valves in motion pulleys are not changed together with the belt early breakdown may wen occur resulting in serious damage to the engine Crankshaft Camshaft pulley Timing belt Injection pump pulley Note Most belt drives on current production engines have recommended change intervals of 160 000klms or more Belt or Chain The benefits of using a belt include
23. the tooth profile of the belt Note Do not mix or match sprockets from similar makes and models during replacement Only replace sprockets from a quality supplier for the specific application Pulleys are constructed of metallic or plastic material and a sealed bearing The pulley bearings are a wear item and must be changed at regular intervals Bearings are lubricated with premium grease and sealed at the factory to extend bearing life On used bearings be sure to look for seepage from the pulley bearing and examine the condition of the seal If you re ever in doubt replace the pulley Also check the condition of the bearing by checking for roughness when turning Never clean bearings or add lubricants as this will shorten bearing life SYSTEMS 10 1 Squeezing or crimping a belt to a small radius can damage the internal cords Timing belts do not stretch so never attempt to force one around a pulley System Components INTRODUCTION TO TIMING BELTS AND SYSTEMS 1019 Tensioners Timing belt drives use three types of tensioning devices that must be installed per the vehicle manufacturer s instructions manual tensioner spring loaded tensioner and hydraulic damper pivot arm Manual Tensioner Manual tensioners use a tension spring to apply the initial tension Hook one end of the Spring to the tensioner and the other end to the engine and tighten the tensioner bolts to 2 the proper torque
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