Steering Diagnostics Service Manual
Contents
1. Are any numbers input on chart below specifications N ne Yes Verify if looseness in the system has been eliminated Reference TMC document RP643 Section 1 Shock Absorbers Call technical service END STEERING WHEEL KICK No Yes cone Gear Adjustment Procedures HFB Valve TAS HFB HF Sector Shaft Binding Darting and Oversteer Occuring once per revolution Cyclic binding at steering wheel More than one U joint No Excessive U joint Angle COMMENT D Check for these Conditions 1 Binding at input side of gear a U joint rubbing TEST 17 b Intermediate shaft binding TEST 19 2 Firewall boot interference cab mount drop TEST 18 3 Gear to frame interfernce TEST 4 4 Binding at king pins steer axle linkage TEST 3 Yes No Vehicle Alignment TEST 21 Yes No Steer Axle Wheel Bearing Adjustment TEST 22 Yes No Check Caster and toe on the front axle Yes No Power Steering Pump TEST 5 COMMENT Yes No Flow Control Response TEST 6 Pump Reference Chart Flow settings according to pump part numbers END BINDING DARTING amp OVERSTEER Yes Column Friction Eccentric Condition Interference TEST 18 U joint Lube or Improperly Phased TEST 17 TEST 19 Yes one Yes one EL Directional Pull Does vehicle pull while bra2. ee ee EE AE EE Re GE EE 9 Steering Wheel Kick iese RE RR EE RE ee ER ee EE Re ee EE ee 10 Binding Darting and Oversteer es EE EE 11 DETTA Pr 12 Road Wander Loose Steering a 13 NORE 14 SAADAAN EE A AA 15 Ne 0100 10 00 E 16 Hard Steering Preliminary Checklist 1 Power steering fluid in reservoir 2 Tire pressure values 3 Fifth wheel properly greased TEST 2 4 Vehicle has not been overloaded Occurs in only one direction Yes Air in System Internal Leak TEST 9 TEST 7 No Intermittent Yes loss of power assist Yes Is I Shaft Binding Intermittent Mechanical TEST 19 Replace I Shaft one Verify problem has been corrected No Intermittent Hydraulic COMMENT K Does oil in reservoir smell hot or burnt Yes Restriction Yes Inspect suspect component found for blockage damage or Restricted Line Replace Component or Hose TEST 10 Verify problem has been corrected No No Call technical No Pump Steering Pump service TEST 5 1 improper hoses and fittings Flow Control Response TEST 46 1 Are any numbers input on chart below as Replace Pump Internal Leak Yes one specifications Verify problem has TEST 7 been corrected No Replace Steering Gear No i Verify problem has Call Ec niga been corrected service Yes E s Pump Vanes Reprime Restricted Lin
3. RW Automotive Commercial Steering Systems Steering Diagnostics Service M anual CHART YOUR WAY TO EASY STEERING E M ar tu hy AIMI A warning describes hazards or unsafe practices which could result in severe personal injury or death VM A caution describes hazards or unsafe practices which could result in personal injury or product or property damage NOTE A note gives key information to make following a procedure easier or quicker Notice This guide was prepared for the purpose of providing general advice concerning the diagnosis and correction of commercial vehicle steering related problems This guide is intended for the use of properly trained professional mechanics NOT Do it Yourselfers Also this guide should be used in conjunction with service manuals provided by both the vehicle and component manufacturers Diagnosis and correction of commercial vehicle steering related problems should only be handled by properly trained professional mechanics who have the proper equipment tools instructions and know how to perform the work properly and safely Power Steering System Analyzer PSSA Gauge Some of the tests in this manual require the use of a PSSA This device is a combination flow meter shut off valve and pressure gauge This tool will allow you to measure flow and pressure and provide a load on the pump through the hydraulic lines of the steering system This tool is required to correctly analyze a steeri
4. and 40 minutes Do not allow the temperature to exceed 250 121 C If the temperature goes over 250 F 121 C or 150 F 66 C above the surrounding temperature ambient at any time during the test stop the test This temperature level is considered extreme and steering system performance and life will be seriously affected Damage to hoses seals and other compo nents may result if operated at extreme temperature If the steering system is operating above the recom mended temperatures the heat problem may be the root cause of the complaint Figure 6 2 HUU Do not keep the load valve closed for more than 5 seconds at a time because damage to the system may result from excessive heat build up Do not allow the pressure to exceed 3000 psi 207 bar 2 With the engine at idle note the flow rate Fully close the load valve until the flow drops to zero Quickly open the load valve observing the flow meter The flow rate must instantly return to the reading you noted above 3 With the load valve open run the engine to governed speed and note the flow rate Fully close the load valve until the flow drops to zero Quickly open the load valve observing the flow meter The flow rate must instantly return to the reading noted above 4 Conduct this pump response test three times at idle and three times at 1500 RPM If the flow rate does not return immediately the pump is malfunctioning which can result in momentar
5. 134613 from Century Lubricants If noise continues check steering wheel and Shroud not applicable to columns with clockspring TEST 28 Steering Column Bearing Check upper bearing gaskets Gaskets should cover bearing TEST 29 Intermediate Column Lash Check intermediate column I Shaft for torsional lash in UJ oints of slip section Replace intermediate column if necessary 33 34 This page intentionally left blank Section 4 Comments Comment A H 2 cccccececececcacecsccceauauaceeeavavaeseeeeavavsesneaeavanans Comment K 39 Comment Some power steering pumps have a temporary state during which the pumping element vanes do not extend Usually increasing engine speed briefly will correct the problem Comment B The maximum speed of steer with power assist for a power steering gear is limited by the pump flow and internal leakage Example Recommended minimum flow for anew TAS65 steering gear is 3 0 gom 11 4 lpm and is based on a maximum steering speed capability of 1 5 steering wheel turns per second Comment C Vehicle linkages are designed to minimize the affect at the steering gear and steering wheel during normal steered axle suspension movements Be sure that linkage used is as specified by vehicle manufacturer Comment D A single u joint operating at an angle will cause a cyclic torque variation at the steering wheel The amount of torque variation increases with the amount of operating angle A s
6. flow is less than the minimum recommended flow for the steering gear used see Steering Gear Flow Requirements chart the pump may not be putting out enough flow for an adequate steering speed If the maximum Figure 5 7 25 system pressure is lower than that specified for the pump refer to your OEM service manual it may not be developing enough pressure to steer If either case exists the pump needs to be repaired or replaced When hydraulic tests are completed and fluid lines are reconnected check fluid level and bleed the air from the hydraulic system Test 6 Pump Flow Control Response IMPORTANT Read the following instructions below before completing Table 6 in the Test Results section 1 Install temperature gauge in reservoir Figure 6 1 Install PSSA in pressure line with shut off valve fully open Figure 6 2 If the temperature goes over 250 F 121 C or 150 F 66 C above the surrounding temperature ambient at any time during the test stop the test This temperature level is considered extreme and steering system performance and life will be seriously affected Damage to hoses seals and other compo nents may result if operated at extreme temperature If the steering system is operating above the recom mended temperatures the heat problem may be the root cause of the complaint JYT TE Do not keep the load valve closed for more than 5 seconds at a time because damage to the system
7. is considered extreme and steering system performance and life will be seriously affected Damage to hoses seals and other compo nents may result if operated at extreme temperature If the steering system is operating above the recom mended temperatures the heat problem may be the root cause of the complaint 2 Run the engine at idle speed NAISE When closing the PSSA shut off valve do so slowly and keep an eye on the pressure gage Do not allow the system to exceed 3000 psi 207 BAR for safety of personne and to prevent damage to the vehicle NE Do not keep the load valve closed for more than 5 seconds at a time because damage to the system may result from excessive heat build up 3 Measure and record the following flow and pressure readings see chart by adjusting the load valve while listening for any unusual noises as the valve is being opened and closed Figures 5 3 5 7 4 Now with the load valve fully open increase the engine speed to governed RPM and measure and record the following flow and pressure readings by adjusting the load valve while listening for any unusual noises as the valve is being opened and closed 5 Determine the recommended flow range and maximum allowable system pressure for the steering system being used by referring to your service manual 6 Compare the minimum and maximum flows and the relief pressure you measured to gear and pump specifications 7 If the minimum measured pump
8. may result from excessive heat build up Do not allow the pressure to exceed 3000 psi 207 bar 2 With the engine at idle note the flow rate Fully close the load valve until the flow drops to zero Quickly open the load valve observing the flow meter The flow rate must instantly return to the reading you noted above 3 With the load valve open run the engine to governed speed and note the flow rate Fully close the load valve until the flow drops to zero Quickly open the load valve observing the flow meter The flow rate must instantly return to the reading noted above 4 Conduct this pump response test three times at idle and three times at 1500 RPM If the flow rate does not return immediately the pump is malfunctioning which can result in momentary loss of power assist When hydraulic tests are completed and fluid lines are reconnected check fluid level and bleed the air from the hydraulic system 24 Figure 6 2 Test b 1 40 Minute Pump Flow Control Response Read the following instructions below before completing Table 6 1 in the Test Results section 1 Install temperature gauge in reservoir Figure 6 1 Install PSSA in pressure line with shut off valve fully open Figure 6 2 Park the vehicle outside Record ambient temperature Run the engine at governed RPM for 40 minutes to bring the fluid up to an elevated testing temperature M easure and record the fluid temperature at the start and at 10 20 30
9. 5 or 70 psi 2 0 2 8 3 8 4 8 bar respec tively The line reservoir pressure drop for a flow of 3 4 5 or 6 gpm 11 15 19 or 23 lpm should not be greater than 20 20 25 or 25 psi 1 4 1 4 1 7 1 7 bar respectively Test 11 Axle Stop Setting Put vehicle steer tires on radius plates turntables Check to make sure axle stops are set to manufacturer s specifications Figure 11 1 Test 12 Pitman Arm and Output Shaft Alignment Look to make sure the output shaft timing mark is lined up with the pitman arm timing mark Some pitman arms have more than one mark so make sure the right one is used Figure 12 1 Test 13 Misadjusted Drag Link The length of the drag link must be correct for the steering system Check the length after you make sure the pitman arm Shaft timing marks are aligned the gear is at its center position and the road wheels are straight ahead Figure 13 1 Test 14 Poppet Setting Procedure 1 If you are working on a newly installed TAS steering gear refer to the service manual to correctly set the poppets If you are working on a steering gear other than a TAS series refer to the OEM s service manual for correct poppet setting instructions 2 To set poppets on a TAS series gear using the adjustable service kit refer to your steering gear service manual Figure 13 1 29 Test 15 Lash in Steering System Two people are needed for this test One person will slowly
10. EST 19 Power Steering Pump TEST 5 COMMENT Steering too Tight TEST 16 Miter Box TEST 20 Firewall Boot Interference Restricted Line TEST 10 QD i Call technical service Yes Yes END NON RECOVERY 14 Shimmy Mechanical Looseness TEST 15 TEST 22 Yes ore No Tire Wheel Balance and Runout COMMENT G Yes one No Air in System TEST 9 COMMENT H Yes ne No Call technical service END SHIMMY 15 OISE NOTE Less than 25 in 6 35 mm at 18 in 547 mm Yes at steering wheel rim is normal Is noise associated with the steering column Is noise mechanical in nature Occurs only when vehicle is stationary Yes Yes No Occurs when vehicle is moving Yes No Occurs only when steering Yes Check if wheel moves side to side relative to column See NOTE Check if shaft is moving in the bearing Location of Shaft in Column TEST 28 Check for loose steering wheel Rubbing or squeaking sound No Is a rattle sound present No and or column mounting Tighten if necessary Hood No Is the related noise originating from under hood or within the cab Cab Call technical service Torque steering gear mounting bolts to OEM Restricted Line TEST 10 specifications on Yes No Low fluid level or loose inlet
11. ation at the steering wheel if the u joints are not in phase with each other Figure 17 1 17 2 f asteering column assembly with multiple u joints is taken apart it must be reinstalled with the timing marks for slip mechanisms aligned This is true for both the cross type and the splined type two piece intermediate shaft Test 18 Steering Column Interference Position steering wheel at the location where steering wheel interference is noticed and look for something interfering or rubbing on the rotating column assembly such as brackets bolts floorboard boot etc Test 19 Intermediate Column Interference 1 Check the slip column by looking to make sure there is proper travel allowance when in use Figure 19 1 2 Look for wear or galling Figure 19 2 3 Check slip column for too much slip force Figure 19 2 31 Test 20 Miter Box Misadjusted if equipped Check and adjust per manufacturer s instructions Figure 20 1 Test 21 Vehicle Alignment Check alignment of steered axle and rear drive axles and trailer axles if problem only exists with trailer Figure 21 1 Test 22 W heel Bearing Adjustment Verify that adjustment is made according to manufacturer s Specification Figure 22 1 Test 23 Air Suspension Adjustment Check and set to manufacturer s specifications Figure 21 1 Test 24 Gear Imbalance 1 Install a low pressure gauge 200 300 psi 14 21 bar maximum with approximately 10 psi 70 ba
12. e COMMENT A TEST 10 Check for these Conditions Cold start only No 1 Binding at input side of gear a U joint rubbing TEST 17 b Intermediate shaft binding TEST 19 2 Firewall boot interference cab mount drop TEST 18 3 Gear to frame interfernce TEST 4 4 Binding at king pins steer axle linkage TEST 3 Power Steering Pump TEST 5 Are any numbers Yes input on chart below Replace Pump specifications Verify problem has been corrected No Chart Steering too Fast COMMENT B TRW Steering Gear Flow Requirements Restricted Line TEST 10 Air in System Yes one TEST 9 No COMMENT H No Check if correct pump has been Internal Leak installed for your TEST 7 application and consult your OEM truck representative END HARD STEERING Reduced Wheelcut Begin Set Axle Stops to OEM Specifications TEST 11 Yes one No Pitman Arm Output Shaft TEST 12 Timing Mark Diagram Figure 12 1 Yes one No Are poppets set correctly on gear Misadjusted Draglink TEST 13 Draglink Diagram Figure 13 1 No Poppet Setting TEST 14 END REDUCED WHEELCUT Steering Wheel Kick 10 Air in System TEST 9 COMMENT H Looseness in Mechanical System TEST 15 TEST 16 Power Steering Pump TEST 5 Shock Absorbers Worn or missing shocks Linkage Geometry COMMENT C Flow Control Response TEST 6
13. econdary couple that side loads the input shaft also in creases with increased u joint angles U joint operating angles of 15 degrees or less will minimize the torque variation felt at the steering wheel Comment E Deflections in the suspension and linkage front and rear due to high engine generated torque levels can cause a steering effect This most often occurs at lower vehicle speeds while accelerating Comment F The location of the axle arm ball center is important during spring wind up conditions such as severe braking A steering arm different from that specified by the manufacturer could cause a steering effect while braking CommentG Soft or loosely supported rear Suspensions may allow the rear driving axles to become non square with the centerline of the chassis during load shifting or trailer roll which will tend to produce a steering effect Comment H Power steering pump cavitation Pump cavitation is defined as a wining or noisy power steering pump Usually pump cavitation is most noticed during engine start up at low temperature extremes However other conditions can cause the power steering pump to continually cavitate and cause intemal pump damage and ultimately failure These conditions are 1 Twisted loose or cracked inlet line 2 Inlet line blockage due to a Contamination dirt and foreign material b Damaged filters c Reservoir components d Inner hose liner separation 3 Displaced improper or improper
14. elief 3 Idle Pump Relief 3 Table 6 0 Test 6 1 40 Minute Pump Flow Control Response Test Start 10 Minutes 20 M inutes 40 M inutes Unit of Measure F or C Unitof Measure PSI or BAR Unit of Measure Pump Relief 1 Idle Pump Relief 1 Pump Relief 2 Idle Pump Relief 2 1500 RPM Pump Relief 3 Idle Table 6 1 1500 RPM 1500 RPM 1500 RPM 1500 RPM Pump Relief 3 1500 RPM PSI or BAR PSI or BAR 41 Test 10 0 Restricted Hydraulic Line Test 42 With PSSA 125 135 F 52 57 C GPM or LPM W ith pressure gauge at pressure line to steering gear at pump end GPM or LPM Remove pressure and return lines and measure pressure with gauge at pump outlet PSI or BAR Table 10 0 Steering Gear Flow Requirements Single Gear TALA 76 oa CN Dual Gear seswa so far 43 Pump Part Number Reference Guide Check the part number on your TRW power steering pump and note the pump relief setting shown in the example below See illustration on where to find the pump part number If the values that you have recorded are within 100 psi 7 bar your pump Is functioning properly If the values recorded are below the negative tolerance your pump is malfunctioning and should be replaced For TRW power steering pumps the relief setting will be the 5th and 6th numbers in the pump part number EV 18 12 15 R 1 01 00 Family designation TJ PS PS P
15. er other components may be required to hold filter element in place inside the reservoir 7 Clean the inside of the reservoir 8 Tum steering wheel from full left to full right 3 4 times This will purge the oil from the steering gear 9 Reconnect pressure and retum lines to the steering gear and tighten 10 Install new filter element into the reservoir 11 Clean reservoir filler cap with an approved solvent Inspect gasket and replace if necessary 12 Fill reservoir with approved replacement fluid and reinstall the filler cap 13 Start engine for 10 seconds stop and check reservoir fluid level and top off if necessary You may need to repeat this procedure 3 or 4 times 14 Upon completion of filling the reservoir start the engine and let it idle At engine idle steer full right and full left once and retum to straight ahead Stop engine and check power steering reservoir level and top off if required 15 Restart engine and steer full turns each direction 3 or 4 times 16 Stop engine and recheck reservoir fluid level and adjust to correct level if needed 17 Inspect system for leaks and correct if necessary 18 Bleed air from the system if required Refer to your steering gear service manual for recommended air bleeding procedures 19 Remove drip pan and lower vehicle Remove blocks from wheels and release vehicle for normal service Comment K Identifying Bumt Oil Sometimes the power steering reservoir oil supply wil
16. gauge in the power steering reservoir MNU Do not allow system pressure to exceed the rating 28 of the gauge during the following procedure or damage to the gauge will result Extremely high restrictions may be indicated with the PSSA gauge as installed with load valve fully open Be sure that the steering gear input shaft is not being restrained from recentering because this will cause a false steering gear pressure drop If there is any question conduct this test with the steering column removed Bring the power steering fluid temperature to 125 135 F 52 57 C at engine idle with no steering force applied to the steering wheel Figure 10 4 At the test engine speed selected from step 2 above measure and record the gauge reading and shut off the engine This measures total system pressure Remove the pressure and retum lines from the steering gear and connect them together with a fitting that will not restrict the flow Figure 10 5 Start the engine and run at the RPM identified in step 2 with the fluid temperature between 125 135 F 52 57 C Measure and record gauge reading and shut off engine This is hydraulic line reservoir pressure The difference between the total system pressure gauge reading and the hydraulic line reservoir pressure gauge reading is the steering gear pressure drop For a TRW steering gear at a flow of 3 4 5 or 6 gpm 11 15 19 or 23 lpm the drop should not be greater than 30 40 5
17. king or accelerating Ye Unequal Braking Force TEST 25 Accelerating COMMENT F Preliminary checklist 1 Vehicle pre alignment TEST 21 2 Wheel bearing adjustment TEST 22 3 Air suspension adjustment TEST 23 4 Steer tires a Swap tires b Belt tread mismatched 5 Vehicle loading Overloaded Unbalanced Gear TEST 24 Power Steering Pump TEST 5 Call technical service Yes Yes END DIRECTONAL PULL 0a Wheel Bearing Adjustment TEST 22 Torque Steer COMMENT E Preliminary checklist 1 Vehicle pre alignment TEST 21 2 Steer tires a Swap tires b Belt tread mismatched 8 Fifth wheel properly greased TEST 2 Yes No Torgue steering gear mounting bolts to OEM specifications Yes No Mechanical Looseness TEST 415 TEST 16 TEST 20 O Yes No Rear Steer Condition COMMENT G Katy Yes No Call technical service END ROAD WANDER d Wander Loose Steering 15 Non Recovery Preliminary Checklist 1 Tire pressure values Entire vehicle TEST 1 2 Fifth wheel properly greased TEST 2 3 Vehicle pre alignment TEST 21 4 Verify caster angle Binding in Steer Axle Linkage or King Pins TEST 3 Gear Column Binding TEST 8 Binding Yi isolated to ee Steering Gear gear or column Gear to Frame Interference TEST 4 Column Checks TEST 18 Driveline Slip Joint Travel and U joint Seizure TEST 17 T
18. l become hotter than the normal operating temperature and overheat This condition may result in an intermittent loss of power assist and also cause deterioration of the power steering hoses and component seals TRW recommends that the power steering hoses be examined for deterioration due to overheated oil which can be identified by wet hoses and determine the condition of the reservoir fluid by looking for signs of bumt oil 37 This page intentionally left blank 38 Section 5 Test Results Test 5 Power Steering Pump Test ees ees ee EE 40 Test 5 1 40 Minute Power Steering Pump Test 40 Test 6 Flow Control Response Test 41 Test 6 1 40 Minute Flow Control Response Test 41 Test 10 Restricted Hydraulic Line Test 42 Steering Gear Flow Requirements ccccssseessseeeeeeeeeeees 43 Pump Part Number Reference Guide 0nnnnnunea 44 39 Test 5 0 Power Steering Pump Test Relief Pressure PSI BAR Engine RPM 1000PS Table 5 0 Test 5 1 40 Minute Power Steering Pump Test 10 Minutes 20 Minutes 30 M inutes 40 M inutes Unit of Measure F or C Relief Pressure PSI BAR Engine RPM 1000P S Table 5 1 40 Test 6 0 Pump Flow Control Response Test Unit of Measure PSI or BAR Unit of Measure Pump Relief 1 Idle Pump Relief 1 Pump Relief 2 Idle Pump Relief 2 Pump R
19. line Yes o Plugged reservoir vent or debris in reservoir Clean and Flush Steering System COMMENT J O Yes No Improperly installed filter in reservoir Yes o No Call technical service 16 Lash in System TEST 15 Is noise due to pump relief valve belt squeal No Yes Is steering wheel touching the column Yes Yes Correct the source of the problem No Lubricate Horn Contact TEST 27 Yes Yes Check I Shaft TEST 29 No Call technical service Yes Call technical service Some noises are normal Inspect to make sure a more serious condition does not exist Yes Call technical service Externa Yes Correct the problem causing the leak and verify it has been Occurs in only one direction fixed No KEN Check the following Loose Defective Overtightened Damaged sealing surface Mismatched fitting Hose connection O ring fitting hardened Hoses Check the following Clamps loose Heat or age cracked Twisting or abrasion wear Misassembled end Loose fitting connection Wet or signs of weeping Test 5 1 ee i Check the following Broken or cracked brackets filler tops connector dipstick Plugged vent hole in filler cap Improper oil level in reservoir Foaming due to filter element being improperly installed Drive shaft seal Cooler Steering Gear Check the following Poppe
20. ly installed filters 4 Reservoir cap vent plugged 36 Comment Excessive Flow TRW steering gears are rated for 8 gom maximum power steering pump flow Although the gears have the capability to handle this maximum flow it is not always a system need or requirement When using combinations of dual gears or a single gear with a hydraulic linear cylinder supply flows for both components should be considered See Steering Gear Flow Requirements Single gear applications have a recommended flow at engine idle For acceptable steering Speed performance again refer to the Steering Gear Flow Requirements Increasing the engine idle flow by more than 50 of the recommended flow can cause power steering system overheating vehicle directional control prob lems Darting and steer axle returnability Non recovery If you measure idle flows above the 50 limit consult your OEM for guidance and recommendations Comment Flushing and Air Bleeding the System IMPORTANT Clean the area around the reservoir steering gear and pump thoroughly before beginning this procedure Set parking brake on vehicle and block rear wheels Raise the front end off the ground Take vehicle out of gear and put into neutral position Raise hood and place a drip pan under the steering gear Remove both the pressure and return lines from the steering gear Remove filter from the power steering fluid reservoir and discard OMA DB IMPORTANT Discard only the filt
21. mplete the tests in order and follow the flow of the chart Locate correct test number in the TEST PROCEDURES section and follow the test procedure When you are done with the test note the results and correct the root cause If condition still exists keep going through the chart if necessary to correct the problem The results of some tests will need to be recorded Use the TEST RESULTS section to record these values If you identify a problem through a test procedure it is important that you retest the vehicle to make sure the condition has been corrected Warranty If you have identified that a steering component on your vehicle needs to be replaced this does not always mean it is warrantable Please read your manufacturer s warranty carefully before submitting a steering component for warranty consideration Definitions 1 Hard Steering Hard Steering is when steering effort at the steering wheel is more than 200 inch pounds typically 18 22 Ibs at the rim of the steering wheel Steering is still possible but there is not enough power assist Common phrases used e Won t turn e Hangs up e Locks up e No assist e Shuts down e Won t tum unless moving Turns hard 2 Reduced Wheelcut Common phrases used e Too great of tuming radius required e Wheelcut restricted e Not enough turns lock to lock 3 Steering Wheel Kick Steering Wheel Kick is when the road wheels hit a bump that the steering wheel reacts to The kick is
22. n the full tum position for longer than 5 to 10 seconds at a time to avoid damaging the pump ya Te KEEP YOUR FINGERS CLEAR OF THE AXLE STOPS AND SPACER BLOCK DURING THIS TEST MAKE SURE THAT THE SPACER BLOCK CONTACTS THE AXLE STOP SQUARELY CONTACT THAT IS NOT SQUARE COULD BREAK THE AXLE STOPS OR DANGEROUSLY THROW OR EJ ECT THE SPACER BLOCK 3 With the fluid temperature between 125 135 F 52 57 C tum the steering wheel until the axle stop bolt contacts the spacer block 4 Apply 20 pounds of force to the rim of the steering wheel during this test to be sure that the steering gear control valve is fully closed Figure 7 5 The pressure gauge should now read pump relief pressure as noted during the Flow Control Response Test Test 46 You can now read steering gear internal leakage on the flow meter 5 Repeat this test for the opposite direction of tum 6 If internal leakage is greater than 1 gpm 3 8 lpm and there is no auxiliary hydraulic linear or rotary cylinder in the system repair or replace the gear If the internal leakage is greater than 2 gpm 7 6 lom and there is an auxiliary hydraulic linear or rotary cylinder in the system controlled by the gear isolate the auxiliary cylinder from the system by disconnecting the auxiliary cylinder hydraulic 26 Figure 7 5 lines at the gear auxiliary ports Plug the steering gear ports with Suitable steel or high pressure plugs or caps In the event that a rotar
23. ng system TRW recom mends that you DO NOT BEGIN TROUBLESHOOTING A STEERING SYSTEM WITHOUT THE USE OF A PSSA If you are not sure how to use a PSSA you may refer to the video available through our website at www trucksteering com This video compliments the tests in this book which require the use of the PSSA A WARNING Throughout this troubleshooting guide test procedures are recommended to help locate the cause of each complaint While performing these tests TRW advises that you TAKE NECESSARY PRECAUTIONS when working with internal vehicle components and hot hydraulic fluids TRW Inc 2002 This page intentionally left blank Table of Contents Ii MR EE RE EE EE 3 Flow Chart Diagrams MANA ANA NAAN 7 Test Procedures AN NADAAN EG GE 19 COME ER ER AR e oon 10 35 TERRE ME AA AA AP 39 This page intentionally left blank Section l Preface Introduction ccccccacaccececscucucucuauauauausueuceeueaeauavauauausesenesenans 3 Understanding the Complaint Reading the Flow Charts Warranty DEFINITIONS Ee ee ee ee ee ee ee ee ee ee ee ee ee 4 5 Hard Steering Reduced Wheelcut Steering Wheel Kick Binding Darting and Oversteer Directional Pull Road Wander Loose Steering Non Recovery Shimmy Noise External Leakage This page intentionally left blank Introduction Understanding the Complaint Steering systems for heavy duty trucks are made up of many components from the steering wheel to the road wheel The pur
24. ou measured to gear and pump specifications 7 If the minimum measured pump flow is less than the minimum recommended flow for the steering gear used See Steering Gear Flow Requirements chart the pump may not be putting out enough flow for an adequate steering speed If the maximum system pressure is lower than that specified for the pump check your manual it may not be developing enough pressure to steer If either case exists the pump needs to be repaired or replaced When hydraulic tests are completed and fluid lines are reconnected check fluid level and bleed the air from the hydraulic system 22 Figure 5 5 Test 1 40 Minute Power Steering Pump Test IMPORTANT Read the following instructions below before completing Table 5 1 in the Test Results section Verify Engine Idle speed per your OEM specifications 1 Install temperature gauge in reservoir Figure 5 1 Install PSSA in pressure line with shut off valve fully open Figure 5 2 Park the vehicle outside Record ambient temperature Run the engine at governed RPM for 40 minutes to bring the fluid up to an elevated testing temperature Measure and record the fluid temperature at the start and at 10 20 30 and 40 minutes Do not allow the temperature to exceed 250 F 121 C If the temperature goes over 250 F 121 C or 150 F 66 C above the surrounding temperature ambient at any time during the test stop the test This temperature level
25. pose of the steering system Is to give the driver directional control of the vehicle When a driver feels the steering control over his her vehicle is not like it should be it is up to you to determine if there is a problem and if so figure out what is causing it It is always easier to fix something if you really understand the complaint Some ways you could do this are e Talk to the driver and ask a lot of questions like what when where and how e Make sure you can feel or see the problem Have the driver show you exactly what he she means e Walk around the truck looking for anything that may be an obvious cause of the problem To make your job easier and faster this manual has both the flow charts and test procedures comments each in their own section Once you have a good understanding of what the complaint is choose the flow chart that best matches the symptoms described to you Because there are different ways to say the same thing we have provided our definitions of the 10 most common complaints in this book Use these to determine which section of the manual would be helpful to begin diagnosing the steering system Reading the flow charts Start the chart at the BEGIN box Follow the lines to the next box answer the question or perform the test to verify the cause of the complaint then proceed to the next step These boxes are arranged in order of likelihood of being the cause of the driver s complaint It is important to co
26. problem is likely in steer axle king pin bushings bearings or linkage Figure 3 2 20 Test 4 Steering Gear Mounting 1 Look for anything between the steering gear and frame that could cause a binding problem For example hoses or brackets that have been routed or are interfering between the steering gear and frame frame flanges or spring mounting points Figure 4 1 Mounting pads lower than steering gear housing lack of clearance between frame and steering gear valve housing adapter sector Shaft adjusting screw and nut contact with access adjustment hole in frame If interference is found correct the problem 2 If the steering gear has been mounted to the frame in a way that causes the gear to distort not be flat it may cause a steering problem Figure 4 2 Checking to see if distortion is present on the vehicle may require the following test 3 With vehicle parked and engine running steer the wheel slowly checking for a binding type of feel at the steering wheel When binding is felt stop engine loosen one mounting bolt restart engine and steer the vehicle again Continue to loosen one mounting bolt at a time shutting off engine each time and check for improvement in the binding condition If improvement is made by loosening the bolts determine by inspection the condition causing the gear to distort and correct the problem Distortion of 030 80 mm or less is acceptable If greater than 030 80 mm surface fla
27. r per division in the pressure line from pump to gear Figure 24 1 Md Do not allow system pressure to exceed the rating of the gauge in the following procedure or damage to the gauge will result 2 Atengine idle slightly tum the steering wheel one direction until a pressure rise is observed at the gauge Figure 24 2 3 Stop steering and gently allow the steering wheel to recenter 4 Next slightly tum the steering wheel the opposite direction while observing the gauge and determine if pressure initially rises or falls with initiation of a tum 5 Repeat test a few times in each direction 6 If aconsistent fall in pressure is associated with the initiation of a tum in one direction the steering gear s control valve is unbal anced and needs to be replaced Test 25 Unequal Brake Force Visually inspect brake assemblies for oil grease on braking sur faces and overall condition of brake surfaces Adjust or replace brakes if necessary 32 Figure 24 2 Test 26 Tire Balance Runout Have wheel assemblies balanced and checked for lateral and radial run out per manufacturer s specifications Preferred method for checking balance is with wheels still on the vehicle Balance includes total rotating assembly TEST 27 Steering Column Noise If column does not include a clockspring remove steering wheel and add dielectric grease to the hom contact The grease TRW uses is Model No K 5 X Semifluid CA product code
28. t screw or sealing nut loose Input Output shaft seals Valve housing sealing areas Side cover seal vent plug bolts side cover gasket Porosity in housing side cover or valve housing END EXTERNAL LEAKAGE Leakage 17 This page intentionally left blank Section 3 Test Procedures Test 1 l4 enn Test 15 LO vo aaa Test 17 HAGI EE EER asana Test 0 72 HAMMAS Test 26 429 ee 19 Test 1 Steer Tire Check 1 Look for Tire damage Uneven or extreme tread wear mis matched tires or other wear indicators that would cause the problem Figure 1 1 2 Check tire pressures on steer axle tires Figure 1 2 Test 2 Fifth Wheel and Trailer Plate 1 Look for dry fifth wheel or trailer plate Figure 2 1 2 Look for damage to fifth wheel or trailer plate Figure 2 2 3 Inspect fifth wheel for looseness Test 3 Steer Axle and Linkage Binding 1 With vehicle steer tires on radius plates turntables or equivalent disconnect the drag link or pitman arm from the steering gear and linkage from assist cylinder if there is one on the vehicle Figure 3 1 HUU Do not steer the gear with linkage removed as misadjustment of automatic poppets may result 2 By hand pull the tire to one axle stop and release engine off The tire should self return to near straight ahead Figure 3 2 3 Repeat the test in the opposite direction 4 If tire does not self retum to near straight ahead a
29. tness condition must be corrected Figure 4 2 21 Test Power Steering Pump Test IMPORTANT Read the following instructions below before completing Table 5 located in the TEST RESULTS section Verify Engine Idle speed per your OEM specifications 1 Install temperature gauge in reservoir Figure 5 1 Install PSSA in pressure line with shut off valve fully open Figure 5 2 2 Runthe engine at 1000 rpm VANUNE When closing the PSSA shut off valve do so slowly and keep an eye on the pressure gauge Do not allow the system to exceed 3000 psi 207 bar for safety of personnel and to prevent damage to the vehicle NN Do not keep the load valve closed for more than 5 seconds at a time because damage to the system may result from excessive heat build up 3 Measure and record the following flow and pressure readings see chart by adjusting the load valve while listening for any unusual noises as the valve is being opened and closed Figures 5 3 5 7 4 Now with the load valve fully open increase the engine speed to governed RPM and measure and record the following flow and pressure readings by adjusting the load valve while listening for any unusual noises as the valve is being opened and closed 5 Determine the recommended flow range and maximum allowable system pressure for the steering system being used by referring to your service manual 6 Compare the minimum and maximum flows and the relief pressure y
30. tum the steering wheel back and forth one quarter turn each way from center with the engine idling The other person should check for looseness at each of the following areas from steering wheel to road wheels Figures 15 1 15 5 Steering wheel to steering column U joints or slip joint and or miter boxes Steering column to steering gear input shaft Steering gear input shaft to steering gear output shaft Pitman arm to output shaft Drag link to pitman arm connection Drag link ends Sockets and adjustable areas Axle arm to drag link connection King pin axle connections bushings Tie rod arms to tie rod connection Tie rod ends sockets and adjustable areas Steering spindle Wheel bearings Lug nuts Spring pin connectors Front axle u bolts Spring hanger brackets rear shackles Cracked or broken components can cause symptoms Similar to loose components but may be more difficult to find NOTE Be sure to check rear drive axles for any looseness and inspect tires for signs of abnormal wear Test 16 Steering Gear Adjustment Check and adjust according to the appropnate service manual for your steering gear if necessary A aa SE pas lt A 30 Figure 15 5 Test 17 U oint Phasing and Lubrication 1 Make sure u joints are properly lubricated 2 Steering column assemblies with more than one universal joint cardan type can cause a cyclic binding feel or torque vari
31. uid level increases when the vehicle is shut off there is an air pocket trapped in the steering gear The increase may not be noticeable depending on the size of the pocket Bleed the steering gear if there is a manual bleed screw at the top of the gear With system at normal operating temperature and engine at proper idle speed and running open the bleed screw and wait until clean clear oil begins to flow from the gear Close the bleed screw and steer the vehicle completely from stop to stop Repeat the bleeding operation three times and recheck oil level in reservoir to make sure there is enough oil for the system to operate properly Figure 9 1 Test 10 Restricted Hydraulic Line Read the following instructions below before completing Table 10 in the Test Results section Look at the supply line that goes to the pump to check for kinking or any other obstructions or irregularities on the inside of the hose Figure 10 1 Install PSSA with load valve fully open Figures 10 2 10 3 Insert temperature gauge into reservoir With oil between 125 135 F 52 57 C determine a test engine speed RPM that causes pump to deliver 3 4 5 or 6 gpm 11 15 19 or 23 lpm which ever is easier and note this speed Remove the PSSA and install a low pressure gauge 200 300 psi 14 21 bar maximum with approximately 10 psi 70 bar per division in the pressure line to the steering gear at the pump end Install a temperature
32. ump EV EV Pump Displacement per revolution 18 18 cc 1 10 cir 22 22 cc 1 34 cir 25 25 cc 1 53 cir 28 28 cc 1 71 cir Flow control 12 12 Ipm 3 17 gpm 14 14 Ipm 3 70 gpm 16 16 Ipm 4 23 gpm 20 20 Ipm 5 28 gpm 24 24 Ipm 6 34 gom Relief setting 09 90 bar 1305 psi 10 100 bar 1450 psi 12 120 bar 1740 psi 14 140 bar 2030 psi 15 150 bar 2175 psi 16 160 bar 2320 psi 17 170 bar 2465 psi 18 185 bar 2683 psi Direction of rotation R clockwise rotation L counterclockwise rotation Shaft type 1 11 tooth 16 32 spline 2 625 dia woodruf key Housing Varies between PS and EV Series pump Customer version 00 Standard 44 TRW Automotive Commercial Steering Systems 800 Heath Street Lafayette IN 47904 Tel 765 423 5377 Fax 765 429 1868 http ww w trucksteering com http trucksteering trw com TRW Inc 2002 TRW 1250 Rev 4 02
33. usually dampened out quickly Common phrases used e Kickback e Backlash e Bump steer 4 Binding Darting and Oversteer Binding is a change or increase in steering wheel effort Binding will usually not require the effort levels described in Hard Steering unless it is severe Darting and oversteer are words that mean the driver suddenly gets more tuming than he she wants 5 Directional Pull Common phrases used e Steering pulls to the right or left e Truck pulls to the right or left e A constant force is required to keep the truck going straight 10 Definitions Road Wander Loose Steering Common phrases used e Lash in steering e Lost motion in steering e Continual corrections are needed at the steering wheel to keep the vehicle from wandering Non Recovery Common phrases used e Wheels don t return to straight ahead Shimmy A severe Shimmy condition can be felt at the steering wheel Typically once something triggers a Shimmy condition to occur it is Sustained until the driver does something Such as slow down to dampen out the condition Common phrases used e Shake at steering wheel Noise Common phrases used e Steering is noisy e Clicking or clunking sound is heard when steering External Leakage Common phrases used Loss of steering fluid e Continual adding of fluid in reservoir required This page intentionally left blank Section 2 Flow Chart Diagrams Hard Steernng EE 8 Reduced Wheelcut
34. y cylinder is used in the system connect the disconnected lines together with a suitable union fitting In the case of a linear cylinder first plug the disconnected lines and then disconnect the cylinder from the steering linkage making Sure it will clear the steered axle Figures 7 6 7 7 Repeat the internal leakage test If the intemal leakage is less than 1 gom 3 8 lpm repair or replace the auxiliary cylinder If the internal leakage is greater than 1 gpm 3 8 lpm repair or replace the gear When hydraulic tests are completed and fluid lines are reconnected check fluid level and bleed the air from the hydraulic system Test 8 Steering Column Binding 1 With the vehicle parked the engine off and the steer axde jacked up slowly steer the vehicle until the binding position is located With the steering gear at this position remove the steering column assembly from the steering gear Note the correct position of the column and steering gear for reassembly after test Figure 8 1 Rotate the steering gear input shaft no more than 1 4 tum each direction and check if binding is still present Figure 8 2 If binding is not felt correct the steering column problem Test 9 Airin Hydraulic System 1 Inspect reservoir for foaming or air bubbles Figure 9 1 If foaming or bubbles are seen air is being sucked into the system through cracks or loose fittings Look for oil level changes engine off versus engine on if fl
35. y loss of power assist When hydraulic tests are completed and fluid lines are reconnected check fluid level and bleed the air from the hydraulic system 25 Test 7 Measured Internal Leakage 1 Install temperature gauge in reservoir Figure 7 1 Install PSSA in pressure line with shut off valve fully open Figure 7 2 PINANG THIS TEST CAN BE DANGEROUS IF NOT PER FORMED CORRECTLY KEEP YOUR FINGERS CLEAR OF THE AXLE STOPS AND SPACER BLOCK DURING THIS TEST MAKE SURE THAT THE SPACER BLOCK CONTACTS THE AXLE STOP SQUARELY CONTACT THAT IS NOT SQUARE COULD BREAK THE AXLE STOPS OR DANGER OUSLY THROW OR EJ ECT THE SPACER BLOCK 2 To test the steering gear for internal leakage you must first prevent operation of the gear s internal unloading poppet valves or relief valve or both in some gears This will allow full pump relief pressure to develop To prevent operation of the poppets place an unhardened steel spacer block about one inch thick and long enough to keep your fingers clear between the axle stop at one wheel Figures 7 3 7 4 To prevent operation of the relief valve remove the relief valve cap o ring and two piece relief valve if equipped from valve housing Install the relief valve plug special tool number J 37130 in its place NOTE Be sure you reinstall the relief valve and valve cap with new o ring back onto the gear after leakage test MNU When running this test do not hold the steering wheel i
Download Pdf Manuals
Related Search