1995 LAND ROVER DISCOVERY brake light

51REAR AXLE AND FINAL DRIVE
4
REPAIR Refit
10.Clean stub axle. Retract ABS sensor slightly
from sensor sleeve, if applicable
11.Fit hub assembly to stub axle.
12.Fit spacing washer.
13.Fit hub adjusting nut. Tighten to
61 Nm.
Back off adjusting nut 90°. Tighten to4 Nm.
This will give the required hub end float of
0,010mm
14.Fit a new lock washer.
15.Fit locknut. Tighten to61 Nm.
16.Tab over lock washer to secure adjusting nut
and locknut.
17.Using a new joint washer fit axle shaft to hub,
secure with five bolts. Tighten to
65 Nm.
18.Fit brake caliper. Tighten to82 Nm.
Secure brake pipes to axle casing.
19.If applicable, set ABS brakes sensor.
Push sensor in until it touches sensor ring then
rotate hub to set sensor.
20.Fit road wheel, remove axle stands and final
tighten road wheel nuts to
126 Nm.
21.Operate footbrake to locate brake pads before
driving vehicle.

BRAKES
1
DESCRIPTION AND OPERATION BRAKES
Discovery vehicles have servo assisted brake
systems and the option of an anti-lock brake system.
Information in this section refers to components
relevant to both brake systems. Where the system
components are different they are referred to as ABS
or NON ABS
BRAKE SYSTEM NON ABS
Description
The servo assisted hydraulic braking system is the
dual line type, incorporating primary and secondary
hydraulic circuits.
NOTE: References made to primary or
secondary do not imply main service
brakes or emergency brakes but denote
hydraulic line identification.
The brake pedal is connected to a vacuum assisted
mechanical servo which in turn operates a tandem
master cylinder. The front disc brake calipers each
house four pistons, these pistons are fed by the
secondary hydraulic circuit. The rear disc brake
calipers each house two pistons, these are fed by the
primary hydraulic circuit via a pressure reducing valve.
A brake fluid level switch is incorporated into the
reservoir cap assembly, the switch will immediately
illuminate a warning light in the instrument binnacle
indicating low fluid or sudden fluid loss.
The brake fluid reservoir is divided, the section closest
to the servo feeds the primary circuit and the section
furthest from the servo feeds the secondary circuit.
Under normal operating conditions both the primary
and secondary circuits operate simultaneously on
brake pedal application. In the event of a failure in the
primary circuit the secondary circuit will still function. If
the secondary circuit fails the primary circuit will still
function. The brake pedal travel will be longer in the
event of a half system failure.If the servo should fail, both hydraulic circuits will still
function but would require greater pedal effort due to
the lack of vacuum assistance. The hand operated
parking brake acts on a brake drum at the rear of the
transfer gearbox and is completely independent of the
hydraulic circuits.
Hydraulic circuit non ABS
Key
A = Primary hydraulic circuit
B = Secondary hydraulic circuit
C = Pressure reducing valve

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.

70BRAKES
8
DESCRIPTION AND OPERATION Brakes applied
When the brake pedal is depressed the pedal pushrod
operates valve C situated in the plastic diaphragm hub
9 and 10. Inital depression of the the brake pedal,
push rod 6 and plunger 7 compress a rubber pad 8.
This slight movement causes valve C to close port D
sealing off the vacuum to chambers 2/4 and allows
atmospheric pressure to enter the chambers through
the air filter E.
With depression in chambers 1/3 and air pressure in
chambers 2/4 the servo hub will apply the brakes via
the master cylinder push rod 13.Atmospheric pressure over the large area of the
diaphragms multiples the force applied to the master
cylinder piston, to provide the power assistance. If the
brake pedal is only partially depressed, the servo hub,
diaphragms and master cylinder push rod will stop
moving, when valve C comes to rest on the plunger 7.
At this point the valve will balance the pressure in all
the chambers, to the applied effort at the pedal and
provide proportional braking.
It is only when the brakes are fully applied that the
valve does not balance the pressures in all the
chambers, but ensures that maximum available
depression is in chambers 1/3 and full atmospheric
pressure enters chambers 2/4.
When the brake pedal is released, the pressure in all
chambers is equalised and the servo is returned to the
rest position by spring 12.

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
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.

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