Defender 300Tdi (1996+). Manual - part 55

STEERING

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. Hose LRT-57-030.
E. Test adaptor LRT-57-001.
F. Pressure gauge LRT-57-005.
G. Thread adaptor LRT-57-004.
H. Thread adaptor LRT-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

. The maximum

power steering system pressure is 77 kgf/cm

2. Under certain fault conditions of the hydraulic

pump it is possible to obtain pressures up to 105
kgf/cm

. 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

(B) Steering wheel held on full lock and engine
idling, 28 kgf/cm

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

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

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 .

STEERING

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 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

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 INTRODUCTION, 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 .

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