electrical LAND ROVER DISCOVERY 1995 Repair Manual

FRONT AXLE AND FINAL DRIVE
1
DESCRIPTION AND OPERATION DESCRIPTION
The welded steel front axle casing houses a separate
spiral bevel type differential unit, which is off set to the
right of the vehicle centre line. The differential unit
drives the front wheels via the axle shafts and
constant velocity joints which are totally enclosed in
the spherical and swivel housings.
The front axles fitted with ABS brakes or non ABS
brakes are of the same construction except for
different top swivel pins in the swivel housing and a
sensor on the constant velocity joint.
Front axle - ABS
The front wheels are pivoted on taper roller bearings
19 at the bottom of the swivel housing and a 'Rialco
bush' 25 at the top. The top swivel pin also houses the
ABS pickup (electrical connection) as shown in the
main illustration, J5367.
Front axle - non ABS
The front wheels are pivoted on tape roller bearings at
the top (see insert) and bottom of the swivel housing.
The wheel hubs on all axles are supported by two
taper bearings and driven by drive flanges which are
splined to the one piece, stub shaft/constant velocity
joint.
Lubrication
The differential, swivel pin housing and wheel hubs
are indiviudally lubricated and separated by oil seals 7
and 8 to prevent oil transfer across the axle when the
vehicle is traversing steep inclines. The wheel
bearings are lubricated with grease and the swivel
housing and differential with oil.
Ventilation
Ventilation of the differential is through a plastic pipe 2
which terminates at a high level in the vehicle on both
ABS and non ABS axles. The swivel housings
ventilate through axle shaft oil seals 8 into the
differential and the hub bearings vent via the oil seals
into swivel housing.

54FRONT AXLE AND FINAL DRIVE
2
DESCRIPTION AND OPERATION
Front axle
1. Axle casing
2. Ventilation pipe
3. Axle shaft
4. Wheel studs and hub
5. Stub axle
6. Wheel bearings (2)
7. Inner and outer hub seals
8. Axle shaft seal
9. Hub lock plate, thrust washer and nuts (2)
10. Brake disc
11. Drive flange
12. Shim washer and circlip
13. Dust cap14. Constant velocity joint/shaft
15. Thrust collar for CV joint
16. Roller bearing
17. Spacer
18. Circlip
19. Bottom swivel taper bearing
20. Top and bottom swivel pins
21. Spherical housing, seal and retainer
22. Swivel housing
23. Constant velocity shaft seal
24. ABS pickup (electrical connection)
25. 'Rialco' bush ABS

BRAKES
3
DESCRIPTION AND OPERATION Description of components
1. ABS Modulator unit
To provide the ABS function a Modulator is positioned
within the system between the master cylinder and the
calipers. On both LHD and RHD vehicles it is sited on
the left inner wing [fender]. The Modulator has 8
solenoid valves, 2 for each wheel, 2 expanders and a
recirculation pump. It is non serviceable.
2. Servo/master cylinder
Actuation of the system is provided by a combined
master cylinder and servo assembly attached to the
pedal box, this provides pressure to opposed piston
calipers at each brake pad Twin piston at the front
axle, single piston at the rear.
3. Pressure reducing valve
To maintain the braking balance, pressure to the rear
axle is regulated by a Pressure Reducing Valve (PRV)
This PRV is of the failure bypass type, allowing full
system pressure to the rear axle in the event of a front
circuit failure. It is sited on the left inner wing [fender].
4. Electronic control unit - ECU
ABS control is provided by an electronic control unit
which is positioned on the passenger side of the
vehicle behind the dash panel/glove box.
The ECU, which is non-serviceable, is connected to
the ABS harness by a 35 way connector. non
serviceable.
The ECU continually monitors the brake system,
providing diagnostics in the event of a system
malfunction. Details of how to access the ECU
diagnostics are provided in the Electrical
Troubleshooting Manual.
5.& 6. Front and rear sensors/exciter rings - 4 off
A sensor is sited at each wheel, sensing a 60 tooth
exciter ring. When vehicle is in motion inductive
sensors send signals to ECU. Front exciter ring is
fitted to outside diameter of constant velocity joint
inside each front hub assembly. The rear exciter ring
is bolted to the rear of each brake disc bell.7. Diagnostic plug connection
A diagnostic plug is located behind the dash. To the
left of the steering column on LHD vehicles. To the
right of the steering column on RHD vehicles. It is a 5
way blue connector.
The location and identification of ABS electrical relays
are given in the Electrical Troubleshooting Manual.
For location and identification of ABS electrical fuses.
See ELECTRICAL, Repair, Fuse Box - Interioror.
See ELECTRICAL, Repair, Fuse Box - Engine
Compartment
ANTI-LOCK BRAKE SYSTEM - ABS
Manufactured by WABCO
Introduction
The purpose of ABS is to prevent vehicle wheels
locking during brake application, thus maintaining
vehicle steerability and stability. This allows vehicle to
be steered whilst brakes are applied, even under
emergency conditions, and to avoid obstacles where
there is sufficient space to redirect the vehicle.
WARNING: ABS is an aid to retaining
steering control and stability while
braking.
·ABS cannot defy the natural laws of physics
acting on the vehicle.
·ABS will not prevent accidents resulting from
excessive cornering speeds, following
another vehicle too closely or aquaplaning,
i.e. where a layer of water prevents adequate
contact between tyre and road surface.
·The additional control provided by ABS must
never be exploited in a dangerous or
reckless manner which could jeopardise the
safety of driver or other road users.
·The fitting of ABS does not imply that the
vehicle will always stop in a shorter stopping
distance.

70BRAKES
4
DESCRIPTION AND OPERATION System description
The brake system consists of dual hydraulic circuits in
a front - rear split. That is individual circuits to front
and rear axles.
Wheelspeed signals are provided by the fitting of
exciter rings to axles and speed sensors.
An ABS stop light switch is fitted to provide a braking
signal to the ECU as well as operate the stop lights.
Electrical wiring is provided as necessary with system
relays and fuses. Discovery Electrical Troubleshooting
Manual gives the location and wiring circuits of these
components.
Visual warning of system malfunction is provided via a
warning light in the instrument panel.
Hydraulic circuit ABS
Key
A = Primary hydraulic circuit
B = Secondary hydraulic circuit
C = Pressure reducing valve
D = ABS ModulatorABS System operation
During normal braking the feel of the brake pedal on
vehicles equipped with ABS will be the same as that
on non ABS vehicles. During ABS cycling the driver
will experience feedback in the form of a pulsating
brake pedal and solenoid/pump motor noise from the
Modulator.
The system is fully automatic in operation both on and
off road, and will only act when the ECU detects that
ABS cycling is necessary. The ECU continually
monitors the operation of the system.
When starting the ABS system will go through a series
of self checks, including a check of the solenoid
valves/pump motor.
WARNING LIGHT
The warning light will be on during the self check
(1.3-2 secs). If no faults are stored in the memory the
light goes out for 0.5sec,then comes on again. It will
then remain on until the vehicle is driven faster than 7
kph/5mph. This is the only time that the light will be on
without indicating a problem.
Any faults detected by the ECU will cause the warning
light to illuminate indicating that the vehicle may not
have full ABS control.

BRAKES
5
DESCRIPTION AND OPERATION BRAKE PIPE LAYOUT ABS
Left hand drive shown. On right hand drive vehicles the master cylinder and servo unit only move
position.
KEY
1. Connector double elbow
2. Rear left brake
3. Modulator to rear left brake
4. Modulator to master cylinder
5. Modulator to pressure reducing valve upper
6. Electrical connection
7. Modulator unit
8. Nut, mounting bush and cup
9. Modulator to front left brake
10. Front left brake
11. Electrical connection12. Modulator to front right brake
13. Modulator to pressure reducing valve lower
14. Master cylinder to pressure reducing valve lower
15. Front right brake
16. Bolt
17. Pressure reducing valve
18. Modulator to pressure reducing valve upper
19. Master cylinder
20. Servo unit
21. Modulator to rear right brake
22. Rear right brake

BRAKES
1
FAULT DIAGNOSIS ABS FAULT DIAGNOSIS
If a fault has occurred, or has been identified by ECU
self diagnostic function and ABS warning light is
illuminated. The system and components must be
checked to locate and rectify fault, using Testbook
diagnostics.
NOTE: If warning lamp has indicated a
fault in system, and no fault code has been
stored in memory, cause of fault is:
a) Failure in electrical supply
b) Bad ECU ground
c) Faulty warning light relay
d) ECU not connected
Before commencing fault diagnosis procedure
following items must be checked:
1.Inspect all exposed cables for damage or
abrasion.
2.Check ground on ABS system.
3.Battery - state of charge.
4.Check hub end-float.
5.All ABS fuses and electrical connections.
Fault rectification
1.Complete harness should be replaced if faults
are found in wiring harness.
2.DO NOT use unspecified cables or connectors,
as this could jeopardise safe function of ABS.
3.DO NOT attempt to open sealed 35 way
connector to ECU.FAULT DIAGNOSIS PROCEDURE
NOTE: If ABS warning light illuminates due
to large sensor air gap, fault will be
retained by the ECU memory. Where wheel
sensors have been pushed fully home prior to
test, The ECU will indicate a fault that has been
rectified.
NOTE: After any steering adjustment,
bearing replacement/adjustment, brake
disc replacement: Check hub end-float and
sensor clearance.
RELAYS AND FUSES ABS
The location and identification of ABS electrical relays
are given in the Electrical Troubleshooting Manual
For location and identification of ABS electrical fuses.
See ELECTRICAL, Repair, Fuse Box - Interioror.
See ELECTRICAL, Repair, Fuse Box - Engine
Compartment

70BRAKES
2
FAULT DIAGNOSIS ABS FAULT AND REMEDY CHART
SYMPTOM POSSIBLE CAUSE CHECK REMEDY
ABS warning light on ABS electrical fault Check ABS electrical
circuit with Testbook
diagnostic equipmentChange component if
necessary
High sensor air gaps Push in sensors
Brake fluid warning light
ONFluid loss Check reservoir fluid level
and inspect system for
leaksRectify leakage, refill
reservoir
Reservoir fluid level
switch malfunctionCheck fluid level switch Change reservoir
cap/switch
Pedal travel increased,
foot pressure normalAir in system Rebleed brake system
Master cylinder
malfunctionChange master cylinder
Pedal can be moved
downwards under
constant pressureSeal leaking in master
cylinderInspect system for leaks Change master cylinder
Seal leaking in servo unit Change servo unit

BRAKES
1
REPAIR GENERAL BRAKE SERVICE PRACTICE
Brake fluid precautions
WARNING: Do not allow brake fluid to
come into contact with eyes or skin.
CAUTION: Brake fluid can damage
paintwork, if spilled wash off immediately
with plenty of clean water.
CAUTION: Use only correct grade of brake
fluid. If an assembly fluid is required use
ONLY brake fluid. Do NOT use mineral oil,
i.e. engine oil etc.
CAUTION: Thoroughly clean all brake
calipers, pipes and fittings before
commencing work on any part of the brake
system. Failure to do so could cause foreign
matter to enter the system and cause damage to
seals and pistons which will seriously impair the
efficiency of the brake system.
·To ensure the brake system efficiency is not
impaired the following warnings must be
adhered to :-
·DO NOT use any petroleum based cleaning
fluids or any proprietary fluids containing
petrol.
·DO NOT use brake fluid previously bled from
the system.
·DO NOT flush the brake system with any fluid
other than the recommended brake fluid.
The brake system should be drained and flushed
at the recommended service intervals.
Cover all electrical terminals carefully to make
absolutely certain that no fluid enters the
terminals and plugs.FLUID LEVEL CHECK / TOP UP
WARNING: Clean reservoir body and filler
cap before removing cap. Use only fluid
from a sealed container.
1.Park vehicle on level ground.
2.Check level is between 'MIN' and 'MAX' marks.
3.If level is below 'MIN' mark top up fluid level to
'MAX' mark on reservoir, using correct fluid.
See
LUBRICANTS, FLUIDS AND CAPACITIES,
Information, Recommended Lubricants and
Fluids
Do not fill reservoir above maximum line

BRAKES
3
REPAIR MASTER CYLINDER ABS
Service repair no - 70.30.08
- Lucas Girling - Type 25.4mm CV/CV
NOTE: This master cylinder is identified by
a 3rd plugged outlet port protruding down
from the master cylinder body.
Before starting repair refer to general brake service
practice.
See General Brake Service Practice
Remove
1.Disconnect battery negative lead.
2.Place a suitable container under master cylinder
to catch brake fluid from cylinder when brake
pipes are disconnected.
3.Thoroughly clean immediate area around all
outlet ports. Remove each brake pipe, sealing
each pipe and outlet port with suitable plugs to
prevent ingress of foreign matter.
4.Disconnect electrical plug from low fluid switch
on reservoir cap.
5.Remove two nuts securing master cylinder to
servo unit remove also spring and plain washers.
6.Detach master cylinder from servo, remove
reservoir cap and drain brake fluid into a
container.Refit
NOTE: Ensure O ring seal between master
cylinder and servo unit is fitted correctly.
7.Fit master cylinder to servo. Secure in position
with two nuts, plain and spring washers. Tighten
to
26 Nm.
8.Fit brake pipes to master cylinder. Tighten to
15Nm.
9.Top-up master cylinder with correct grade of
brake fluid.
See LUBRICANTS, FLUIDS AND
CAPACITIES, Information, Recommended
Lubricants and Fluids
10.Bleed system.See Brake System Bleed
11.Fit cap, reconnect electrical lead to fluid level
switch. Reconnect battery negative lead.

70BRAKES
4
REPAIR MASTER CYLINDER NON ABS
Service repair no - 70.30.08 - Remove
Service repair no - 70.30.09 - Repair
- Lucas Girling - Type 25.4mm AS/AS
WARNING: This master cylinder is not
suitable to be fitted on vehicles with
antilock brake systems.
Before starting repair refer to general brake service
practice.
See General Brake Service Practice
Remove
1.Disconnect battery negative lead.
2.Place a suitable container under master cylinder
to catch brake fluid from cylinder when brake
pipes are disconnected.
3.Thoroughly clean immediate area around all
outlet ports. Remove each brake pipe, sealing
each pipe and outlet port with suitable plugs to
prevent ingress of foreign matter.
4.Disconnect electrical plug from low fluid switch
on reservoir cap.
5.Remove two nuts securing master cylinder to
servo unit remove also spring and plain washers.
6.Detach master cylinder from servo, remove
reservoir cap and drain brake fluid into a suitable
container.Repair
7.Thoroughly clean master cylinder and inspect
outer surfaces for damage and condition, renew
complete assembly if necessary.
8.Using two soft jaws, clamp master cylinder
flange in a suitable vice. Remove water ingress
'O' ring seal from master cylinder to servo flange
and discard.
9.Grip outside of transfer housing with a suitable
pair of pliers, carefully pull, working pliers in a
backwards and forwards rocking motion to ease
housing off master cylinder. Discard housing and
vacuum seal.