Land Rover Defender 300tdi Workshop 3rd Edition Rover Manual
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57STEERING 4 DESCRIPTION AND OPERATION Rotary valve misaligned Demand for assistance (Valve misaligned) When the steering wheel and input shaft is turned, steering resistance transmitted to the worm causes the torsion bar to be twisted and the valve ports to be misaligned for a right or left turn. The misalignment of the valve ports directs all fluid pressure A to one side of the piston only and allows displaced fluid B on the other side. When demanding maximum assistance, any excessive fluid output from the pump due to high pump speed, will circulate through the regulator valve located in the pump unit, causing the temperature of the fluid and the pump to rise rapidly.CAUTION: To avoid excessive fluid temperatures which could damage the oil seals, the steering must not be held on full lock for more than 30 seconds in one minute. Only when the steering wheel, and the demand for assistance, is released, will the torsion bar return the valve to neutral, allowing the fluid to circulate through the reservoir where it is cooled. In the unlikely event of mechanical failure of the torsion bar, a coarse splined connection (7) between the input shaft and worm, ensures steering control is maintained sufficient to allow the vehicle to be recovered.
STEERING 5 DESCRIPTION AND OPERATION Pump and regulator valve operation The pump which is belt driven from the engine is an eccentric roller type and also houses the pressure regulator and flow control valve. The pressure is controlled by a spring loaded ball valve (3) which is housed inside the flow control valve piston (4). No demand for assistance High flow through box - Low pressure With no demand for assistance the rotary valve in the steering box acts as a pressure relief valve, allowing fluid (A) to flow freely through the steering box and back to the reservoir and pump inlet (B). No demand for assistance 1.Reservoir 2.Pump 3.Pressure control ball valve and spring 4.Flow control valve and spring 5.Press fit plug (ball bearing) 6.Restrictor The ball plug (5) is pressed into the valve (4) during manufacture and determines the opening pressure of pressure relief valve (3).No flow, through box - High pressure When the steering is turned, the rotary valve effectively stops all fluid flow through the steering box, thus causing an increase in pressure (A). This increase in pressure is felt in the flow control valve spring chamber where, at a pre-determined pressure the relief valve (3) will open and allow the pressure to escape. The fall in pressure in the flow control spring chamber, allows the flow control valve to move to the right, which in turn allows pump output (A) to escape directly into the pump inlet (B). Assistance demanded As soon as the steering wheel is released after making a turn, the system reverts to the condition seen in J6292 and the road wheels are returned to the straight ahead position by the mechanical steering geometry. In the event of any hydraulic failure, steering control, though heavy, will be maintained through the mechanical components in the steering box.
STEERING 1 FAULT DIAGNOSIS INSUFFICIENT POWER ASSISTANCE 1.Is fluid level correct? YES - go to 3. NO - Fill/bleed sytem 2.Is problem a leak? YES - Diagnose See Power Steering Fluid Leaks . NO - continue 3.Is drive belt tension correct? YES - go to 5. NO - Is drive belt worn or contaminated with oil? See ELECTRICAL, Repair, Auxiliary drive belt . 4.Is problem resolved? YES - end NO - continue 5.Carry out pressure test at idle and 1000 rev/min. See Power Steering System - Test. 6.Is correct pressure achieved? YES - steering box defective Not at any speed go to 9. Not at idle go to 7. 7.Is idle speed correct? YES-Goto8. NO - Correct idle speed - See ENGINE TUNING DATA, Information, 300 Tdi Engine . 8.Is problem resolved? YES - end NO - go to 9. 9.Bypass steering box using adaptor tap LRT-57-001 10.Is correct pressure obtained? YES - defective steering box NO - defective steering pump CAUTION: Do not hold steering wheel on full lock for more than 30 seconds in any one minute to avoid overheating fluid and possibly damaging seals. NOTE: 1. Excessive pressure in the system is almost always caused by a faulty relief valve in the PAS pump. NOTE: 2. Insufficient pressure in the system is usually caused by low fluid level or PAS pump drive belt slip, or one of the following: PAS system leaks, faulty PAS pump relief valve, fault in steering box valve and worm assembly, leak at piston in steering box, worn components in PAS pump or box.
57STEERING 2 FAULT DIAGNOSIS POWER STEERING SYSTEM - TEST NOTE: If steering lacks power assistance. Check pressure of hydraulic pump before fitting new components. Use fault diagnosis chart to assist in tracing faults. A. Steering box. B. Steering pump. C. Existing hose, steering box to pump. D. HoseLRT-57-030. E. Test adaptorLRT-57-001. F. Pressure gaugeLRT-57-005. G. Thread adaptorLRT-57-004. H. Thread adaptorLRT-57-022.Procedure 1.A hydraulic pressure gauge and test adaptor is used to test power steering system. This gauge is able to measure 140 kgf/cm 2. The maximum power steering system pressure is 77 kgf/cm2. 2.Under certain fault conditions of the hydraulic pump it is possible to obtain pressures up to 105 kgf/cm 2. It is important to realise that pressure on gauge is same pressure being exerted upon steering wheel. When testing, turn steering wheel gradually while reading pressure gauge. 3.Check and maintain maximum fluid level of reservoir. 4.Examine power steering units and connections for leaks. All leaks must be rectified before attempting to test the system. 5.Check steering pump drive belt tension and renew belt if necessary, See ELECTRICAL, Repair, Auxiliary drive Belt . 6.Assemble test equipment and fit to vehicle, as shown in RR3959M. 7.Open tap of adaptor. 8.Bleed system, take care not to overload pressure gauge. 9.With system in good condition, pressures should be: (A) Steering wheel held on full lock and engine running at 1,000 rev/min, 70 to 77 kgf/cm 2. (B) Steering wheel held on full lock and engine idling, 28 kgf/cm 2. Checks should be carried out on both full lock positions. CAUTION: Do not maintain this pressure for more than 30 seconds in any one minute to avoid overheating fluid and possibly damaging seals. 10.Release steering wheel and with engine idling. Pressure should read below 7 kgf/cm 2. 11.If pressures differ to those given a fault exists. 12.To determine if fault is steering box or pump. Close adaptor tap for a maximum five seconds. 13.If gauge does not register specified pressure, pump is faulty. 14.Fit a new pump, bleed system and repeat test. If low pressure or a substantial imbalance exists, fault is in steering box valve and worm assembly.
STEERING 3 FAULT DIAGNOSIS STEERING DAMPER The power steering system, as well as reducing the effort required to manoeuvre the vehicle when parking, also helps to dampen any deflections of the road wheels, being transmitted back to the steering wheel. When operating the vehicle off road, the road wheels are often deflected by ruts and boulders causing the steering wheel to turn left and right. This phenomenon is known as steering kickback. To subdue the effects of steering kickback, a hydraulic damper is fitted in the steering linkage between the track rod and the differential casing. The damper, which offers the same resistance in extension and compression, is sealed for life. Steering damper check Check the condition operation of the hydraulic steering damper as follows: Check procedure 1.Inspect damper for casing damage or leaks. 2.Clamp one end of the damper horizontally in a vice using soft jaws. Compress and extend the unit by hand. Resistance should be equal in both directions. 3.If it is felt that the unit is outside acceptable limits, fit a new steering damperSTEERING FAULTS Symptom:- Excessive kickback through steering wheel - when driven on rough terrain. 1.Is the steering damper in good working order? See Steering Damper. NO - Renew unit See Repair, Steering Damper . YES - Continue. 2.Is there any looseness or free play in the steering ball joints and linkage? YES - See Steering Linkage Inspect. NO - Continue. 3.Is there any looseness or worn bushes in front suspension? YES - See FRONT SUSPENSION, Repair, Radius Arm . NOTE: When replacing suspension bushes ALL bushes and fixings must be replaced. NO - Continue. 4.Is the steering exceptionally light/sensitive when driven on good road surface? YES - See fault symptom -Steering excessively light/sensitive and freeplay at steering wheel. NO - Suspect axle swivel resistance. 5.Check the resistance of the axle swivels See FRONT AXLE AND FINAL DRIVE, Overhaul, Front Stub Axle, Constant Velocity Joint and Swivel Pin Housing .
57STEERING 4 FAULT DIAGNOSIS Symptom:- Fluid leaks from steering box seals. CAUTION: The steering wheel must not be held on full lock for more than 30 seconds in one minute, as this may overheat the fluid and cause damage to the oil seals. 1.Check fluid level See Repair, Power Steering Fluid Reservoir . Check fluid pressure See Power Steering System - Test . 2.Is pressure high? YES - Renew pump See Repair, Power steering Pump . If oil seal leaks persist after renewing the pump See Overhaul, Power Steering Box. NO - See Overhaul, Power Steering Box. Symptom:- Insufficient power assistance - castor return action normal. 1.Are tyres correct type and pressure? NO - See GENERAL SPECIFICATION DATA, Information, Wheels and Tyres . YES - Continue. 2.Is fluid level correct? NO - Check fluid level See Repair, Power Steering Fluid Reservoir . YES - Check system for air locks See Repair, Power Steering System - Bleed . 3.Is pressure correct? NO - Check fluid pressure See Power Steering System - Test . If pressure is not correct after bleeding the system, renew pump See Repair, Power Steering Pump . YES - See Overhaul, Power Steering Box.Symptom:- Steering heavy - stiff, poor castor return action. 1.Are tyres correct type and pressure? NO - See INTRODUCTION, Information, Wheels and Tyres . YES - Check universal joints for seizure and correct alignment See Repair, Lower Steering Shaft and Universal Joints . Check power steering box adjustments See Overhaul, Power Steering Box . 2.Is the power assistance satisfactory? NO - See fault symptomInsufficient assistance, (castor return action normal). YES - Disconnect drag link from drop arm and check steering column and box for stiffness See Repair, Drag Link and Drag Link Ends . 3.Is the steering stiff with the drag link disconnected? NO - Check steering ball joints for seizure and axle swivels lubrication and resistance See Repair, Drag Link and Drag Link Ends ,See FRONT AXLE AND FINAL DRIVE, Overhaul, Front Stub Axle, Constant Velocity Joint and Swivel Pin Housing . YES - Disconnect the lower steering shaft and check the column and box for stiffness See Repair, Lower Steering Shaft and Universal Joints . 4.Is the steering column stiff to turn when disconnected from the box? NO - Remove and overhaul box See Overhaul, Power Steering Box . YES - Adjust steering column See Stiff Steering Checklist .
STEERING 5 FAULT DIAGNOSIS REV: 05/99 Symptom :- Steering excessively light/sensitive. Excessive freeplay at steering wheel. 1.Are steering box adjustments correct? NO - See Adjustment, Power Steering Box. WARNING: Adjustments of steering box should not be required while in warranty period. If box is within warranty, it must be returned to manufacturer. No attempt must be made to introduce backlash. YES - Suspect worn panhard rod or radius arm bushes. Check condition of ball joints and the lower steering column shaft universal joints for wear See Repair, Lower Steering Shaft and Universal Joints . Symptom :- Steering vibration, road wheel shimmy - wobble. Vibration through the steering linkage powerful enough to induce high frequency oscillation of the steering wheel, is generally caused by out of balance road wheels. However there are a number of other possible causes of this symptom which if severe, may be described as shimmy or wobble. Regardless of the terminology used by the owner/driver to describe the symptoms, the following diagnostic checks should be carried out in the order presented. 1.Check the tyres and balance of the road wheels See GENERAL SPECIFICATION DATA, Information, Wheels and Tyres ,See WHEELS AND TYRES, Fault diagnosis, Fault - Symptoms See WHEELS AND TYRES, Repair, Wheel Balancing . 2.Check the steering hydraulic damper function See Steering Damper. 3.Check steering column universal joints for wear and correct alignment See Repair, Lower Steering Shaft and Universal Joints .4.Check steering linkage ball joints for wear, correct alignment and security, including steering box and tie rod See Steering Linkage Inspect . 5.Check all front suspension rubbers for wear. Check all fixing torques, including radius arm bushes, panhard rod and anti-roll bar See FRONT SUSPENSION, Repair, Panhard Rod , See FRONT SUSPENSION, Repair, Radius Arm ,See FRONT SUSPENSION, Repair, Anti-Roll Bar ,See FRONT SUSPENSION, Repair, Front Shock Absorber . 6.Fit new radius arm bushes using NTC 6781. Fit new nuts, bolts and washers. 7.If problem persists fit damper kit STC 288 - 90, STC 290 - 110/130 (2 off front) and STC 289 - 90, STC 291 - 110 levelled, STC 292 - 110 unlevelled, STC 293 - 130 (2 off rear). Road test vehicle. 8.Check the power steering box adjustments and operation See Overhaul, Power Steering Box. 9.Check the hub bearing end floats and determine the condition of the hub bearings as applicable See FRONT AXLE AND FINAL DRIVE, Repair, Front Hub Assembly . 10.Check the resistance and condition of the swivels See FRONT AXLE AND FINAL DRIVE, Description and operation, Description . If problem is not diagnosed: Repeat checks starting at 1. 11.Carry out a full steering geometry check See GENERAL SPECIFICATION DATA, Information, Steering .
57STEERING 6 FAULT DIAGNOSIS STEERING STABILITY AND VEER UNDER BRAKING Possible cause: Incorrectly set, swivel pin bearing preload. Remedy. 1.Follow instructions to overhaul front stub axle, constant velocity joint and swivel pin See FRONT AXLE AND FINAL DRIVE, Overhaul, Front Stub Axle, Constant Velocity Joint and Swivel Pin Housing .1. GENERAL STEERING 1.Carry out visual and safety checks See Visual and Safety Checks . 2.Road test vehicle See Road Test Procedure. 3.Is problem resolved? YES - end NO - continue 4.Is problem stiff steering? YES - See Stiff Steering Checklist. NO-Goto6. 5.Is problem resolved? YES - end NO - go to 8. 6.Is problem steering niggle ? YES - Replace radius arm bushes, arm and axle See FRONT SUSPENSION, Repair, Radius Arm . NO - go to 8. 7.Is problem resolved? YES - end NO - continue. 8.Centralise steering box See Adjustment, Centralise Steering Box . 9.Is problem resolved? YES - end NO - continue. 10.Check, adjust if necessary, steering geometry. 11.Is problem resolved? YES - end NO - continue. 12.Categorise the remaining problems into one or more of the following descriptions: See 2. Steering Veer. See 3. Veer Under Braking. See 4. Directional Stability.
STEERING 7 FAULT DIAGNOSIS 2. STEERING VEER From 1. GENERAL STEERING: 1.Vehicle veers, not under braking, swap front tyres side to side. 2.Is problem resolved? YES - end NO - continue. 3.Does vehicle now veer in other direction? YES - fit new tyres NO - continue. 4.Recentralise steering box See Adjustment, Centralise Steering Box. 5.Is problem resolved? YES - end NO - contact local technical office.3. VEER UNDER BRAKING From 1. GENERAL STEERING: 1.Vehicle veers under braking, bleed brake system. 2.Is problem resolved? YES - end NO - continue. 3.Check brake pads for glazing, and discs, axles etc for contamination. 4.Is problem resolved? YES - end NO - continue. 5.Check brake lines and hoses for deterioration. Replace as necessary. 6.Is problem resolved? YES - end NO - continue. 7.Contact local technical office.
57STEERING 8 FAULT DIAGNOSIS 4. DIRECTIONAL STABILITY From 1. GENERAL STEERING: 1.Is directional stability concern when vehicle is towing? YES - Check towing/vehicle loading parameters in Owners Handbook. NO - go to 3. 2.Is problem resolved? YES - end NO - continue. 3.Check condition of rear trailing link/chassis bushes. 4.Is problem resolved? YES - end NO - continue. 5.Check condition of front and rear shock absorbers. If necessary, change units in pairs, side to side. 6.Is problem resolved? YES - end NO - continue. 7.Check steering damper See Steering Damper . 8.Is problem resolved? YES - end NO - continue. 9.Check wheel balance 10.Is problem resolved? YES - end NO - contact local technical office.POWER STEERING FLUID LEAKS 1.Is fluid level correct? YES - go to 3. NO - Refill or drain to correct level. Bleed system, check for leaks See Repair, Power Steering System - Bleed. 2.Is problem resolved? YES - end NO - continue. 3.Are hoses or joints leaking? Check on full lock with engine at 2000 rev/min. YES - loosen and retorque joints. NO - go to 6. 4.Does leak remain? YES - change PAS pipe. NO - end. 5.Does leak remain? YES - suspect seal in component. Check and replace as necessary. NO - end. 6.Is oil escaping from filler cap? YES - bleed system See Repair, Power Steering System - Bleed. NO - go to 8. 7.Is oil still escaping from filler cap? YES - go back to 1. NO - end. 8.Is oil leaking from PAS pump? YES - go to 10. NO - continue. 9.Is oil leaking from PAS box? YES - go to 10. NO - end. 10.Clean unit, add tracer dye to system. Retest 11.Is oil still leaking? YES - establish leak point. Repair or replace unit as necessary. NO - end.