1995 LAND ROVER DISCOVERY ECU

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
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

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.

70BRAKES
6
REPAIR
NOTE: The primary plunger assembly
cannot be broken down any further and is
serviced as a complete unit. Discard
assembly.
15.The secondary plunger assembly will remain at
bottom of master cylinder bore. Remove tapping
assembly on a piece of wood until plunger
appears at cylinder mouth, carefully pull plunger
out of master cylinder.
16.If swirl tube was not expelled at same time as
secondary plunger, repeat above operation to
remove it from bottom of master cylinder bore
and discard.
17.Clean all parts with unused brake fluid. Place
cleaned parts onto a clean sheet of paper.
Inspect cylinder bore and plungers for signs of
corrosion, ridges and score marks. Provided
working surfaces are in perfect condition, new
seals from a Girling Service repair kit may be
used.
Renewing secondary plunger seals
18.Remove following components from secondary
plunger and discard:
NOTE: A small screwdriver with end
rounded off and polished is required to
remove 'L' seal. DO NOT damage
secondary plunger.
(A) Springs
(B) Seal retainer
(C) Recuperating seal (primary cup)
(D) Washer
(E) 'L' seal

BRAKES
7
REPAIR 19.Coat new seals in unused brake fluid. Fit 'L' seal
to plunger.
20.Fit washer followed by recuperating seal. Fit seal
retainer and springs, ensure springs are
correctly seated.
Assembling master cylinder
CAUTION: It is important that following
instructions are carried out precisely,
otherwise damage could be caused to new
seals when inserting plungers into cylinder bore.
Generous amounts of new brake fluid should be
used to lubricate parts during assembly.
21.Fit new swirl tube to bottom of cylinder bore.
22.Lubricate secondary plunger and cylinder bore.
Offer plunger assembly to cylinder until
recuperation seal is resting centrally in mouth of
bore. Gently introduce plunger with a circular
rocking motion, as illustrated. Ensuring that seal
does not become trapped, ease seal into bore
and slowly push plunger down bore in one
continuous movement.
23.Fit new primary plunger assembly using same
method as for secondary plunger.
24.Fit original guide ring to support primary plunger.
25.Coat a new 'O' ring with brake fluid and fit to its
respective groove on outer location surface of
master cylinder.
CAUTION: Do not roll 'O' ring down outer
location surface of master cylinder. It
should be slightly stretched and eased
down cylinder and into its groove. Do not over
stretch seal.
26.Fit new retaining ring on outer surface of master
cylinder ensuring that serrations of ring are
facing mounting flange.
27.Fit two new reservoir seals in respective ports.
28.Fit a new vacuum seal to either primary plunger
or to bottom of transfer housing bore, open face
of seal towards primary plunger.
29.Lubricate vacuum seal with brake fluid. Fit
transfer housing to master cylinder, push
housing fully up to cylinder mounting flange, Do
not adjust transfer housing after fitting.
30.Lubricate new water ingress seal with brake
fluid, Slightly stretch seal and ease down
housing until it is in position between housing
and flange.
31.Roll reservoir into top of master cylinder,
reversing procedure described in instruction 10.
Refit
NOTE: Ensure O ring seal between master
cylinder and servo unit is fitted correctly.
32.Fit master cylinder to servo. Secure in position
with two nuts, plain and spring washers. Tighten
to
26 Nm.
33.Fit brake pipes to master cylinder. Tighten to
15Nm.
34.Top-up master cylinder with correct grade of
brake fluid.
See LUBRICANTS, FLUIDS AND
CAPACITIES, Information, Recommended
Lubricants and Fluids
35.Bleed system.See Brake System Bleed
36.Fit cap, reconnect electrical lead to fluid level
switch. Reconnect battery negative lead.

70BRAKES
8
REPAIR MASTER CYLINDER ASSEMBLY NON ABS
Key to master cylinder
1. Water ingress seal
2. Transfer housing
3. Vacuum seal
4. Guide ring
5. Retaining ring
6. 'O' ring seal7. Primary plunger assembly
8. 'L' seal
9. Secondary plunger
10. Washer
11. Recuperating seal (primary
cup)
12. Seal retainer13. Springs (2 off)
14. Swirl tube
15. Master cylinder body
16. Reservoir seals
17. Reservoir
18. Low fluid level switch and
cap
NOTE: Thoroughly check that no debris is lodged in fluid passageways and drillings. If debris is
found, carefully remove, re-clean cylinder and re-check.

BRAKES
9
REPAIR SERVO ASSEMBLY
Service repair no - 70.50.01
Remove
Before starting repair refer to general brake service
practice.
See General Brake Service Practice
NOTE: The filter, non-return valve and
grommet, are the only serviceable
components, in event of failure or damage
fit a new unit.
1.Disconnect battery negative lead.
2.Disconnect electrical plug to low fluid level
switch.
3.Thoroughly clean immediate area around all
master cylinder outlet ports. Remove each brake
pipe, sealing each pipe and outlet port to prevent
ingress of foreign matter.
4.Disconnect vacuum supply hose to servo.
5.Remove lower dash panel to gain access to
servo push rod to brake pedal.
6.Remove clevis pin securing servo push rod to
brake pedal.
7.Remove two nuts and plain washers securing
servo.
8.Remove servo and master cylinder assembly.
9.Drain brake fluid into a suitable container. (If
master cylinder is kept horizontal it is not
necessary to drain fluid).10.Detach spacer from pedal box mounting face of
servo.
NOTE: Retain spacer for reassembly. The
spacer ensures stringent pedal to servo
operating dimensions are maintained.
11.Remove master cylinder from existing servo and
refit to new servo, if fitting new unit.
Refit
12.Fit spacer to servo.
13.Fit servo to pedal box.
14.Lightly grease brake pedal around area servo
push rod pivots.
15.Fit push rod to lower hole of brake pedal. Fit
clevis pin and clip.
16.Secure servo with two nuts and plain washers.
Tighten nuts to
26 Nm.
17.Refit lower dash panel.
18.Fit master cylinder to servo, refit nuts, plain and
spring washers. Tighten nuts to
26 Nm.
19.Remove all sealing plugs. Refit brake pipes to
respective ports. Tighten brake pipes to
15 Nm.
20.Refit vacuum supply hose.
21.Fill master cylinder to correct level using correct
grade of brake fluid.
See LUBRICANTS,
FLUIDS AND CAPACITIES, Information,
Recommended Lubricants and Fluids
22.Bleed brake system.See Brake System Bleed