Defender 90 NAS. Instruction - page 53
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 damper
STEERING 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.
57
STEERING
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 GENERAL SPECIFICATION DATA,
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 symptom Insufficient
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
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 [sway] bar
See FRONT SUSPENSION, Repair, Panhard
Rod, See FRONT SUSPENSION, Repair,
Radius Arm, See FRONT SUSPENSION,
Repair, Anti-Roll Bar Assembly, See FRONT
SUSPENSION, Repair, Front Shock
Absorber.
6. Fit new radius arm bushes using NTC 6860. Fit
new nuts, bolts and washers.
7. If problem persists fit damper kit STC 241 (2 off
front) and STC 1474 (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
INTRODUCTION, Information, Steering.
57
STEERING
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 - Go to 6.
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 .