steering wheel LAND ROVER DISCOVERY 1999 Owner's Manual

STEERING
DESCRIPTION AND OPERATION 57-3
1Air bag module
2Steering wheel and nut
3Horn switch 2 off
4Radio remote control switch (if fitted)
5Column switches
6Lower nacelle
7Column tilt adjustment lever
8Steering column lock
9Ignition switch and harness
10Upper column assembly
11Lower column
12Universal joint 13Bolt
14Bolt
15Intermediate shaft assembly
16Decouple joint
17Rubber coupling and heat shield
18Bolt
19Universal joint
20Shear bolt 2 off
21Rotary coupler
22Upper nacelle
23Cruise control switch (if fitted)

STEERING
DESCRIPTION AND OPERATION 57-5
Description
General
The major steering components comprise an impact absorbing telescopic steering column, a Power Assisted Steering
(PAS) box, a PAS pump, and fluid reservoir. Hydraulic fluid from the fluid reservoir is filtered and then supplied
through the suction line to the inlet on the PAS pump. The PAS pump supplies fluid to the steering box through a
pressure line routed above the front cross member. Fluid returns to the reservoir along the same route through a
return line. On LH drive vehicles the pipe route above the front cross member is still used, the length of pipe acting
as an oil cooler.
To minimise driver's injury in the event of an accident the steering system has a number of safety features including
a collapsible steering column. An additional safety feature is an air bag located in the steering wheel.

+ RESTRAINT SYSTEMS, DESCRIPTION AND OPERATION, Description - SRS.
Steering column assembly and intermediate shaft
The steering column central shaft comprises of two shafts, the upper shaft is splined to accept the steering wheel and
located in bearings in the column tube. A universal joint is located on the bottom of the upper shaft, the joint allows
for angular movement between the upper and lower shafts. The lower shaft is made in two parts, the top section of
the lower shaft is located outside of the lower section. The two sections of the lower shaft are connected by two nylon
injection moulded shear pins. The lower shaft goes through a lower bearing attached to the bulkhead, the lower shaft
is connected by a universal joint to the intermediate shaft in the engine compartment.
Steering column
An upper column tube provides for the location of the steering lock and ignition switch and also the steering switch
gear and a rotary coupler. The rotary coupler provides the electrical connection for the steering wheel mounted airbag,
switches and horn. The upper mounting bracket has two slots, a slotted metal bracket is held in each slot by four resin
shear pins.
The column is mounted on four captive studs which are located on a column mounting bracket. The captive studs
pass through the metal brackets, locknuts secure the steering column to the bulkhead. The two lower mountings are
fixed and cannot move when loads are applied to them. The upper mounting is designed to disengage or deform when
a load is applied, allowing the column to collapse in the event of an accident. The steering column must be replaced
as a complete assembly if necessary.
When an axial load is applied to the upper column tube, energy absorption is achieved by the following mechanism:
lthe mounting bracket deforms,
lthe resin shear pins holding the slotted metal brackets shear,
lthe top mounting bracket slides out of the slotted metal brackets.
The slotted metal brackets remain on the captive studs on the bulkhead. If the column mounting moves, injection
moulded shear pins retaining the two sections of the lower column shaft will shear. This allows the two sections of the
lower shaft to 'telescope' together.
In the event of a collision where the steering box itself moves, two universal joints in the column allow the intermediate
shaft to articulate, minimising movement of the column towards the driver. If movement continues energy absorption
is achieved by the following mechanism:
lthe decouple joint in the intermediate shaft will disengage,
lthe lower section of the steering column shaft will move through the lower bearing,
lthe injection moulded shear pins retaining the two sections of the lower column shaft will shear.
This allows the two sections of the lower shaft to 'telescope' together reducing further column intrusion. Protection to
the drivers face and upper torso is provided by an SRS airbag module located in the centre of the steering wheel.

+ RESTRAINT SYSTEMS, DESCRIPTION AND OPERATION, Description - SRS.

STEERING
57-6 DESCRIPTION AND OPERATION
Tilt adjustment
The column tilt adjuster lever mechanism is located on the LH side of the steering column and allows the upper column
tube, nacelle and steering wheel assemblies to be tilted up or down a maximum of 7.5° or 47 mm (NAS vehicles have
a smaller range of movement than the ROW vehicles).
The pawl of the mechanism is attached to the lower column and is allowed to pivot, a toothed quadrant is fixed to the
upper column tube.
When the lever on the LH side of the steering column is raised the mechanism releases the pawl from the toothed
quadrant, this allows the column to be moved. When the lever is released two return springs pull the pawl into
engagement with the toothed quadrant.
Steering column lock (All except NAS)
The steering column lock houses the ignition switch, ignition illumination light ring, key lock barrel and the alarm
passive coil. The steering lock is attached to the upper column with two shear bolts. The bolts are tightened to a
torque which shears off the heads of the bolts preventing easy removal of the steering lock.
The steering lock operates by a bolt, which emerges when the ignition key is turned to position 'O' and the ignition key
removed. The bolt engages in a lock collar located on the upper shaft in the upper column tube. The lock collar is
attached to the upper shaft by a 'wave form' interference ring. If a high torque is applied via the steering wheel with
the lock engaged, the lock collar will slip on the upper shaft. This prevents damage to the steering lock, yet still
prevents the vehicle from being driven.
Steering column lock (NAS only)
The steering column lock houses the ignition switch, ignition illumination light ring, key lock barrel and the alarm
passive coil. The steering lock is attached to the upper column with two shear bolts. The bolts are tightened to a
torque which shears off the heads of the bolts preventing easy removal of the steering lock.
The steering column lock operates by a bolt, which emerges when the ignition key is turned to position 'O' and the
ignition key removed. The bolt engages in a groove machined into the upper shaft in the column tube.
Steering wheel
The steering wheel comprises a cast centre and wire frame onto which the soft polyurethane foam is moulded. The
steering wheel is located on the upper column shaft by a spline and is secured with a nut. A remote radio control switch
(if fitted) is located on the LH side of the steering wheel, a cruise control switch may be located on the RH side. Horn
switches are located on each side of the centre of the steering wheel and protrude through the airbag module cover.
Both switches are connected by wires to the rotary coupler connector.
Intermediate shaft
One end of the intermediate shaft is attached to the steering column lower shaft by a splined universal joint and a bolt,
the universal joint is part of a rubber coupling assembly. The rubber coupling assembly is covered by a heat shield
and connects to the lower section of the intermediate shaft via a decouple joint. The rubber coupling reduces the
shocks felt by the driver through the steering wheel. A second universal joint on the other end of the intermediate shaft
is held in by a bolt. The universal joint is splined and engages with the splined rotor (input) shaft of the steering box.
The decouple joint consists of a metal plate that has open ended slots, the plate is bolted through the slots into the
other half of the decouple joint. The top half of the decouple joint has a slot that accepts the lower section of the
intermediate shaft. The slotted metal plate clamps the lower section of the intermediate shaft to the top section. An
indicator clip is installed between the slotted metal plate and the top half of the decouple joint.
If the intermediate shaft is compressed in an accident, the slotted metal plate in the decouple joint will disengage if
sufficient force is applied to the front end of the shaft. If the forces involved do not disengage the shaft, the red
indicator clip located in the decouple joint will break off if the shaft moves. The intermediate shaft cannot be repaired
and must be replaced as an assembly if accident damage occurs.

STEERING
57-8 DESCRIPTION AND OPERATION
Steering box
The steering box is located behind the first cross member of the chassis and is secured to the chassis rail with four
bolts. The steering box is of the worm and roller type and has a rotary control valve. The steering box is connected to
the steering knuckles of the front road wheels by the drop arm, drag link and track rod. The steering box is lubricated
by the hydraulic fluid in the housing. The input shaft is attached to the steering wheel via the intermediate shaft and
steering column. The drop arm is secured to the output shaft with a nut and tab washer. A ball joint allows movement
between drop arm and drag link, the ball joint is secured with a locknut. The steering box requries approximately 3.5
turns from lock to lock.
As a maintenance aid, an alignment bolt can be used to lock the drop arm at the steering box centre position. The bolt
fits in a groove in the rear face of the drop arm and screws in to a threaded hole on the bottom of the steering box
housing.
Cross section through steering box
1Relief valve stop 2 off
2Relief valve 2 off
3Piston
4Rack
5Housing
6Output shaft
7Roller
8Valve rotor9Torsion bar
10Input shaft
11Pin
12Valve sleeve
13Course spline
14Worm gear
15Spline (worm gear to torsion bar)

STEERING
DESCRIPTION AND OPERATION 57-11
Rotary control valve in demand mode
1Worm gear
2Torsion bar
3Valve sleeve
4Pin5Input shaft and valve rotor
6Piston/rack
7Coarse spline
8Spline (torque shaft to worm gear)
When the steering wheel and input shaft is turned steering resistance transmitted to the worm causes the torsion bar
to be wound up and the valve ports in the valve rotor and valve sleeve to be aligned for a right or left turn. The
alignment of the valve ports directs fluid pressure 'A' from the PAS pump to one side of the piston/rack . The other
side of the piston/rack is now connected to return 'B' (due the valves port alignment) and displaced fluid returns to the
reservoir. The pressure difference in the cylinder on each side of the piston gives the power assistance to move the
rack and so turn the steering.
The greater the resistance of the road wheels to the steering rotary movement, the greater torque acting on the torsion
bar and input shaft causing greater changes of alignment of the ports in the valve. As the change of alignment
becomes greater, the fluid pressure passing to the applicable side of the piston/rack increases.
Only when the steering wheel stops turning and the torsion bar has unwound, will the valve rotor return to the neutral
position. In the neutral position the fluid circulates through the ports in the valve rotor and valve sleeve and back to
the reservoir where it is cooled.

STEERING
DESCRIPTION AND OPERATION 57-15
As the pump rotor rotates towards the pump inlet the volume between the roller vanes and the pump housing
increases, this action causes a depression in the chamber between the pump roller vanes and the housing. As the
rotation continues the chamber is opened to the pump inlet, and the depression in the chamber causes fluid to be
drawn in. The roller vanes continue past the inlet port, closing off the inlet port and trapping the fluid in the chamber
between the rollers and the pump housing.
The internal 'cam' shape of the pump housing causes the rollers to move closer together as the pump rotor rotates
towards the outlet port. The reduced volume of the chamber between the roller vanes causes the fluid to become
pressurised. When the chamber is opened to the outlet port of the pump the fluid escapes at high pressure. The roller
vanes continue turning and go past the outlet port, closing off the chamber between the two roller vanes.
As rotation continues the inlet sequence begins again. The inlet and pressurisation/outlet sequences continue as the
pump rotates, and is repeated between each two roller vanes. The pump is a positive displacement type and the
potential pump output increases with engine (drive pulley) speed. The pressure relief and flow control valve regulates
flow/pressure by diverting fluid back to the pump inlet through internal recirculation passages in the pump body.
Steering damper
The steering damper is located behind and just below the first cross member of the chassis. The ends of the steering
damper have steel 'eyes' welded on, rubber bushes are installed in each 'eye'. The steering damper is attached
between brackets on the chassis rail and the drag link. Each end of the steering damper is secured by a bolt and
locknut. The hydraulic damper absorbs shocks in the steering, caused by road wheel deflections when operating on
rough terrain.

STEERING
57-16 DESCRIPTION AND OPERATION
Operation
Hydraulic fluid is supplied to the PAS pump inlet from the PAS reservoir, the PAS pump draws in and pressurises the
fluid. The PAS pump self regulates internal flow rates and operating pressure, and supplies pressurised fluid from the
PAS pump outlet to a rotary control valve in the steering box. At neutral the fluid is circulated by the PAS pump and
flows around the system at a lower pressure and a constant flow rate. With most of the fluid being returned to the
reservoir the pressure inside the system remains very low. When a control input turns the rotary control valve in the
steering box, pressure in the system will rise as the control valve directs fluid to give power assistance.
The action of turning the steering wheel turns the steering column and intermediate shaft. The intermediate shaft turns
the input shaft of the steering box. The input shaft moves the rotary control valve in the steering box, the rotary valve
controls the pressure used inside the steering box for power assistance. The input shaft also turns a worm gear, the
worm gear acts on a roller attached to the output shaft. As the worm gear turns the roller, the roller travels along the
lands of the worm gear. As the roller is attached to the output shaft the output shaft turns.
As the output shaft of the steering box turns, hydraulic pressure is supplied via the rotary control valve to the steering
box. The hydraulic pressure acts on a rack that assists with the movement of the output shaft of the steering box. A
drop arm is attached to the output shaft of the steering box. The drop arm is connected to a drag link by a ball joint.
The drag link is connected via ball joints to one front steering knuckle and road wheel. A track rod connected to this
steering knuckle links the two steering knuckles together. As one steering knuckle and road wheel is turned by the
drag link, the other steering knuckle and wheel is moved by the track rod.

STEERING
ADJUSTMENTS 57-17
ADJUST ME NTS
Steering box - check and adjust
$% 57.10.13
Check
1.Raise front of vehicle.
WARNING: Do not work on or under a
vehicle supported only by a jack. Always
support the vehicle on safety stands.
2.Remove nut securing drag link to drop arm.
3.Using LRT-57-036, break taper joint and
release drag link.
4.Ensure steering is centralised.
5.With the drop arm held, check for rotational
movement at the intermediate shaft universal
joint. If any movement exists, the steering box
requires adjusting.Adjust
1.Loosen lock nut on steering box adjuster and
tighten adjuster until movement is removed at
universal joint.
CAUTION: Ensure that steering box is
centralised before adjustment. Never over
adjust, free play should just be eliminated.
2.When adjustment is correct, hold the adjuster
and tighten adjuster locknut.
3.Turn steering wheel from lock to lock and check
no tightness exists.
4.Fit drag link to drop arm, and tighten nut to 80
Nm (59 lbf.ft).
5.Remove stands and lower vehicle.

STEERING
57-18 ADJUSTMENTS
Hydraulic system - bleed
$% 57.15.02
Bleed
1.Clean PAS fluid reservoir around filler cap and
fluid level indicators.
2.Remove filler cap from PAS fluid reservoir. If
necessary, fill PAS fluid reservoir to upper level
indicator with recommended fluid.

+ CAPACITIES, FLUIDS,
LUBRICANTS AND SEALANTS, Fluids.
CAUTION: Ensure no dirt is allowed to enter
the steering reservoir when the cap is
removed.
3.Start engine and run to normal operating
temperature.
4.Position container to catch fluid spillage from
steering box.
5.With engine at idle speed, and an assistant
turning the steering from lock to lock, loosen
bleed screw on top of steering box. Keep PAS
fluid reservoir topped up and allow all air to
bleed from system. When fluid from bleed
screw is free of air, tighten bleed screw.
CAUTION: Do not hold steering at full lock
for longer than 10 seconds.
6.Stop engine.
7.Clean spilled PAS fluid from steering box and
surrounding area.
CAUTION: Power steering fluid will damage
paint finished surfaces. If spilled,
immediately remove fluid and clean area
with water.
8.Check fluid level in PAS fluid reservoir and fill to
upper level mark. If fluid is aerated, wait until
fluid is free from bubbles.
9.Fit PAS fluid reservoir filler cap.
Steering linkage - centralise
$% 57.35.05
The following procedure assumes that the front
wheel alignment is correctly adjusted.
Adjust
1.Raise front of vehicle, and position the road
wheels at straight ahead.
WARNING: Do not work on or under a
vehicle supported only by a jack. Always
support the vehicle on safety stands.
2.Remove nut securing drag link to drop arm.
Using tool LRT-57-036 break taper joint and
release drag link from drop arm.
3.Fit centralising bolt to steering box and ensure
that front road wheels are in the straight ahead
position.
4.Loosen clamp bolts on drag link.

STEERING
ADJUSTMENTS 57-19
5.Adjust drag link so that taper joint is centralised
in drop arm, then tighten drag link clamp bolts:
Tighten M8 bolts to 22 Nm (16 lbf.ft) and M10
bolts to 33 Nm (24 lbf.ft).
6.Connect drag link to drop arm and tighten nut to
80 Nm (59 lbf.ft).
7.Remove steering box centralising bolt.
8.Remove stand(s) and lower vehicle.
9.Road test the vehicle and check that the
steering wheel is centralised. If steering wheel
is not centralised, proceed as follows.
10.Slacken drag link adjuster clamp bolts.
11.Without disconnecting drag link from drop arm,
adjust the length of the drag link to bring the
steering wheel to the central position.
CAUTION: Repositioning the steering wheel
on its splines cannot correct small (less
than 5°) errors in steering wheel alignment.
Always rectify small errors in alignment by
adjusting the drag link as detailed above,
ensuring that steering box centralisation is
maintained.
12.Tighten drag link clamp bolts: Tighten M8 bolts
to 22 Nm (16 lbf.ft) and M10 bolts to 33 Nm (24
lbf.ft)
Wheel alignment - front
$% 57.65.01
The following is the only wheel alignment equipment
which has been approved.
lBeissbarth ML 4600 wheel alignment computer
(6 sensor).
lBeissbarth ML 4600-8 wheel alignment
computer (8 sensor).
lBeissbarth ML 4000 wheel alignment computer
(8 sensor wireless).
lHunter S411-14.
Check
1.Ensure tyre pressures are correct and vehicle
is at kerbside weight.
2.Roll vehicle backwards and forwards to relieve
stresses in steering and suspension.
3.Ensure road wheels are positioned straight
ahead.
4.Ensure that wheel alignment equipment is
properly calibrated.
5.Following the equipment manufacturer's
instructions, measure the front wheel
alignment. Compare with the figures given in
General Data.

+ GENERAL DATA, Steering.
Adjust
1.Loosen track rod and adjuster clamp bolts.
2.Rotate adjuster to obtain correct alignment.

+ GENERAL DATA, Steering.
3.Tighten track rod and adjuster clamp bolts:
Tighten M8 bolts to 22 Nm (16 lbf.ft) and M10
bolts to 33 Nm (24 lbf.ft).
4.Recheck front wheel alignment.