wheel LAND ROVER DEFENDER 1996 Repair Manual

STEERING
3
DESCRIPTION AND OPERATION Rotary valve operation
Rotary valve at neutral
The rotary valve assembly comprises a worm (1),
valve sleeve (2), input shaft (4) and torsion bar (5).
The valve sleeve is retained inside the worm by a trim
screw (3), and incorporates valve ports in its inner
bore. The input shaft is attached to the steering wheel
via a steering shaft and steering column and
incorporates valve ports in its outer diameter to align
with those in the sleeve.
The torsion bar, which is secured to the worm and
input shaft with pins (6) at each end, holds the valve
ports in neutral alignment when there is no demand
for assistance.No demand for assistance (Valve at neutral)
When there is no demand for assistance the torsion
bar holds the input shaft and sleeve valve ports in
neutral relationship to one another, allowing equal
pump pressure (A) to both sides of the piston/rack (9).
Any excess fluid flow from the pump returns to the
reservoir via (B).

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
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 Owner's 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.

57STEERING
10
FAULT DIAGNOSISREV: 05/99 VISUAL AND SAFETY CHECKS
WARNING: Before taking vehicle out on
the public highway for road test, it is
important that the following basic visual
checks are carried out to ensure that the vehicle
complies with legal requirements.
Tyres and wheel rims
1.Check and adjust tyre pressures
See
GENERAL SPECIFICATION DATA,
Information, Tyre Pressures
.
Note that this information refers to standard tyres
fitted as original equipment.
2.Check condition of tyres. Inspect for signs of
uneven wear, damage and feathering. Check
tread depth.
3.Ensure that the tyre make, type and general
condition are common across each axle.
4.Check wheel rims for signs of damage and
excessive run out.
5.Carry out road test
See Road Test Procedure
.
ROAD TEST PROCEDURE
General steering/handling problems can usually be
classified into one of the categories listed and ARE
GENERALLY RELATED TO THE AGE, CONDITION
AND USE OF THE VEHICLE.
WARNING: Ensure that all road tests are
conducted by suitably qualified drivers in
a safe and legal manner, and where local
traffic conditions allow.
1.Carry out visual and safety checks
See Visual
and Safety Checks
.
Confirm general nature of complaint with customer,
simulating where possible the conditions under which
the problem occurs. Carry out following road test
procedure to establish the problem.2.Steering load assessment - drive at 16 km/h (10
mph). Put 90°turn input into steering wheel,
check self centering. The self centering should
be equal on each lock but not necessarily return
to exactly straight ahead without assistance from
the driver.
3.Steering assessment - drive at 64 km/h (40 mph)
on a staight FLAT road (no camber), check for
steering veer. The vehicle should follow a
straight path with NO tendency to follow a
curved path. If vehicle veers towards the kerb,
vehicle may be 'camber sensitive'. A small
amount of veer in direction of camber is
acceptable.
4.Directional stability assessment - drive at 112
km/h (70 mph) or maximum legal speed on a
straight flat road. Carry out a normal lane
change. Vehicle should quickly settle into a new
straight path.
5.Braking assessment (medium effort) - drive at 96
km/h (60 mph) on a straight flat road. Apply
steady medium braking effort, noting any
tendency to veer. Carry out brake test three
times, if a veer is consistently noted carry out a
braking efficiency test on a rolling road.
6.Braking assessment (full effort) - drive at 96
km/h (60 mph) on a straight flat road. Apply full
braking effort, noting any tendency to veer. Carry
out brake test three times, if a veer is
consistently noted carry out a braking efficiency
test on a rolling road.
If the symptom described by the customer is stiff
steering or steering niggle, carry out stiff steering
procedure
See Stiff Steering Checklist.
If not, proceed with basic checks and adjustments
See Visual Check and Basic Adjustments.