wheel LAND ROVER DISCOVERY 1999 Workshop Manual

BRAKES
DESCRIPTION AND OPERATION 70-19
ABS sensors
The ABS sensors supply the SLABS ECU with a sinusoidal speed signal from each wheel. An inductive sensor,
installed in the hub bearing of each wheel, senses off a 60 tooth exciter ring integrated into the inner race of the hub
bearing. Each ABS sensor has a fly-lead connecting it to the vehicle wiring.
HDC switch
The HDC switch is a latching push switch installed on the fascia, in the switchpack inboard of the steering wheel.
When pushed in, the switch connects an ignition supply to the SLABS ECU to initiate HDC.
Warning indications
The SLABS ECU operates audible and visual warnings to convey brake system status.
Audible warning
A repetitive chime, at a frequency of 2 Hz, draws attention to warning lamp indications. The chime is produced on the
speaker in the instrument pack.
Warning lamps
1ABS warning lamp
2HDC fault warning lamp
3ETC warning lamp4HDC information warning lamp
5Brake warning lamp (all except NAS)
6Brake warning lamp (NAS only)
The following brake system warning lamps can be found in the instrument pack:
lA red brake graphic (all except NAS vehicles) or red BRAKE legend (NAS vehicles), to warn of low brake fluid
level, handbrake on and brake control system failure affecting EBD.
lAn amber ABS graphic, to warn of brake control system failure affecting the ABS function.
lAn amber TC graphic, to warn of brake control system failure affecting the ETC function.
lTwo inclined vehicle graphics, one amber (fault) and one green (information), to indicate operating status of HDC
and to warn of brake control system failure affecting the HDC function.
Each warning lamp is illuminated by a separate LED. The ABS, brake and ETC warning lamps are continuously on
while illuminated; the two HDC warning lamps are either continuously on or flash at a frequency of 2 Hz while
illuminated.

BRAKES
70-20 DESCRIPTION AND OPERATION
Operation
Refer to illustration.

+ BRAKES, DESCRIPTION AND OPERATION, Brake system control diagram.
When the ignition is switched on, the SLABS ECU performs a check of the brake related warning lamps as part of the
power up procedure. The warning lamps are illuminated for approximately 3 seconds and then extinguished. If a fault
warning lamp remains illuminated after the lamp check, a fault has been detected and repair action is required.
ABS
The ABS function prevents the road wheels locking during brake application, thus maintaining vehicle stability even
under emergency conditions.
WARNING: ABS is an aid to retaining steering control and stability while braking:
lABS cannot defy the natural laws of physics acting on the vehicle.
lABS will not prevent accidents resulting from excessive cornering speeds, following another vehicle too
closely, aquaplaning, etc.
lThe 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.
lThe fitting of ABS does not imply that the vehicle will always stop in a shorter distance.
NOTE: 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 anti-lock braking operation the driver will experience feedback in the form of a pulsating
brake pedal and solenoid/pump motor noise from the ABS modulator.
The anti-lock braking function is automatically enabled whenever the ABS modulator is in the normal braking mode.
While the anti-lock braking function is enabled, if the SLABS ECU detects a wheel decelerating faster than the
average and at the calibrated wheel slip limit for ABS operation, it operates the ABS modulator in the ABS braking
mode for the affected wheel.
EBD
The EBD function optimises the distribution of hydraulic pressure between the front and rear axles, under all vehicle
load configurations and road conditions, to maintain vehicle stability during braking. EBD operates in forward and
reverse and is automatically enabled whenever the ABS modulator is in the normal braking mode at vehicle
deceleration rates of 0.3 g and above (i.e. medium to high brake pedal loads). EBD operation is similar to that of ABS,
but is calibrated to intervene at lower wheel slip limits and operates the brakes in axle pairs instead of individually.
During braking, if the SLABS ECU detects the wheels of one axle going slower than those of the other axle, i.e. a
potential wheel slip situation, it signals the ABS modulator to close the inlet solenoid valve for the brakes of the slower
wheels. This prevents any further increase in hydraulic pressure to those brakes, while allowing the hydraulic pressure
to the brakes on the other axle to increase and so maximise the overall braking effort. If the wheel speeds of the axle
being subjected to EBD control return within the calibrated wheel slip limits, the SLABS ECU signals a stepped
opening of the inlet solenoid valves, which allows a progressive increase of hydraulic pressure to the related brakes.
Operation of EBD is detectable from a stiffening of brake pedal movement as the inlet solenoid valves close and a
slight pulsing of the brake pedal as the inlet solenoid valves open. EBD operation ceases immediately the brake pedal
is released.
The wheel slip limit for EBD operation varies with vehicle speed. During normal operation, the inlet solenoid valves
always operate in axle pairs, with only one axle pair closed at any one time. Since the most lightly loaded wheel during
a braking manoeuvre will usually be the first to reach the slip limit, under most vehicle load configurations and road
conditions EBD control occurs on the trailing axle. However, EBD control can occur on the leading axle or switch
between axles during the braking manoeuvre.

BRAKES
DESCRIPTION AND OPERATION 70-21
ETC
The ETC function uses brake intervention to prevent wheel spin and maintain even torque distribution to the wheels.
ETC is automatically enabled while the brakes are off at speeds up to 62.5 mph (100 km/h), and operates the brakes
either individually or in axle pairs:
lAt speeds up to 31.3 mph (50 km/h), ETC uses individual brake intervention to maintain even torque distribution
between wheels on the same axle.
lVehicles up to 03 model year – At speeds between 0 and 62.5 mph (0 and 100 km/h), ETC also uses brake
intervention in axle pairs to maintain even torque distribution between the front and rear axles. In effect, this mode
of operation replaces the centre differential lock of the transfer box which, although still incorporated, is non
operational under normal driving conditions.

+ TRANSFER BOX - LT230SE, DESCRIPTION AND OPERATION, Description. If the centre differential
lock is in the locked condition, the SLABS ECU illuminates the ABS and ETC warning lamps and inhibits the ETC
function (the ABS, EBD and HDC functions are retained, but at degraded performance levels).
lVehicles from 03 model year (with differential lock fitted) – At speeds between 0 and 62.5 mph (0 and 100
km/h), ETC uses brake intervention in axle pairs to maintain even torque distribution between the front and rear
axles. If the centre differential lock is in the locked condition, the differential lock warning lamp in the instrument
pack is illuminated. The ABS, EBD, ETC and HDC functions are retained, but with revised parameters to suit the
locked differential.
While the ETC function is enabled, if the SLABS ECU detects a wheel accelerating faster than the average, indicating
loss of traction, it operates the ABS modulator in the active braking mode. Depending on the vehicle speed, active
braking is employed for either the brake of the affected wheel or for both brakes on the affected axle, until all four
wheels are driven at approximately the same speed again. During active braking the SLABS ECU also illuminates the
ETC warning lamp, for a minimum of 2 seconds or for the duration that ETC is active. ETC operation is desensitised
during 'hard' cornering.
HDC
HDC uses brake intervention to provide a controlled descent ability in off road conditions when engine braking is
insufficient to maintain a comfortable speed. This allows the driver to leave HDC selected and to control the vehicle's
descent speed, down to the system's minimum target speed, using only the accelerator pedal. The HDC function is
selected on/off by a switch on the fascia. When selected on, HDC is enabled in all forward gears and reverse provided:
lVehicle speed is below 31.3 mph (50 km/h).
lThe transfer box is in low range.
lOn manual gearbox vehicles, the clutch is engaged.
When HDC is enabled, the HDC information warning lamp illuminates. If HDC is selected outside the above
conditions, the HDC information warning lamp flashes and the audible warning sounds continuously.
When HDC is enabled, the SLABS ECU calculates a target speed from the throttle position element of the engine data
input, and compares this with actual speed. If the actual speed is higher than the target speed, the SLABS ECU
operates the ABS modulator in the active braking mode to slow the vehicle down to the target speed. While the braking
force is being applied, the SLABS ECU also energizes the brake lamp relay to put the brake lamps on. Active braking
is discontinued while vehicle speed is below the target speed or if the foot brakes are applied. Applying the foot brakes
during active braking may result in a pulse through the brake pedal, which is normal.
During active braking, the brakes are operated predominantly on the wheels of the leading axle, but if that is not
sufficient to achieve the required deceleration the brakes of the trailing axle are also applied. The deceleration rate is
dependent on the speed differential between initial vehicle speed and the target speed. The deceleration rates are
relatively low at higher speed differentials, then progressively increase as vehicle speed approaches the target speed.
Anti-lock braking is also enabled during active braking, but at very low speeds some wheel lock can occur.
The target speed increases as the accelerator pedal is pressed, from a programmed minimum with the accelerator
pedal released, up to a maximum of 31.3 mph (50 km/h). For any given accelerator pedal position, while travelling
uphill or on level ground the target speed is always greater than the corresponding vehicle speed, which allows the
vehicle to be driven normally without HDC intervention. However, when travelling downhill, the gravitational effect on
the vehicle means that for any given accelerator pedal position the target speed is less than the corresponding vehicle
speed, and HDC intervenes to limit vehicle speed to the target speed.

BRAKES
DESCRIPTION AND OPERATION 70-25
DESCRIPTION AND OPERAT ION
Handbrake component layout
1Warning switch
2Handbrake lever
3Cable
4Protective sleeve
5Drum brake6'C' clip
7Threaded sleeve
8Adjuster wheel
9Base plate
10Transmission tunnel

BRAKES
70-26 DESCRIPTION AND OPERATION
Description
General
The handbrake consists of a drum brake, installed on the rear of the transfer box, operated by a cable connected to
a handbrake lever between the front seats.
Handbrake lever
The handbrake lever is mounted on a base plate which attaches to the transmission tunnel. A conventional ratchet
and thumb operated release button are incorporated for locking and unlocking the lever. A warning switch on the base
of the lever operates the brake warning lamp in the instrument pack. While the handbrake is applied the warning
switch connects an earth to the instrument pack which, if the ignition is on, illuminates the brake warning lamp. In
some markets, the instrument pack performs a bulb check of the brake warning lamp each time the ignition is switched
on.
Cable
The handbrake cable consists of inner and outer cables installed between the handbrake lever and the drum brake.
A protective sleeve is installed on the cable to protect the cable from heat from the exhaust system. Handbrake
adjustment is provided by a threaded sleeve installed on the outer cable where it locates in the handbrake lever.
Turning an adjuster wheel, which is keyed to the threaded sleeve and secured by a 'C' clip, alters the effective length
of the outer sleeve and consequently changes the handbrake lever movement needed to apply the drum brake.

BRAKES
REPAIRS 70-33
REPAIRS
Brake disc - front
$% 70.12.10
Brake discs must be renewed in pairs, unless
one disc requires changing before 1000 miles
(1500 km) from new.
Remove
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 road wheel(s).
3.Remove 2 bolts securing brake caliper to
swivel hub.
4.Release caliper and tie aside clear of brake
disc.
CAUTION: Do not allow caliper to hang on
brake hose.
5.Remove screw securing disc to drive flange.
6.Remove brake disc from drive flange Refit
1.Clean mating faces of drive flange and new
disc.
2.Fit brake disc to drive flange, fit screw and
tighten to 13 Nm (10 lbf.ft).
3.Clean mating faces of caliper and hub.
4.Fit caliper, and tighten bolts to 175 Nm (129
lbf.ft).
5.Fit road wheel(s) and tighten nuts to 140 Nm
(103 lbf.ft).
6.Remove stand(s) and lower vehicle.

BRAKES
70-34 REPAIRS
Brake disc - rear
$% 70.12.33
Brake discs must be renewed in pairs, unless
one disc requires changing before 1000 miles
(1500 km) from new.
Remove
1.Raise rear 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 road wheel(s).
3.Remove 2 bolts securing brake caliper to rear
hub.
4.Release caliper and tie aside clear of brake
disc.
CAUTION: Do not allow caliper to hang on
brake hose.
5.Remove screw securing disc to drive flange.
6.Remove brake disc from drive flange. Refit
1.Clean mating faces of drive flange and new
disc.
2.Fit brake disc to drive flange, fit screw and
tighten to 13 Nm (10 lbf.ft).
3.Clean mating faces of caliper and hub.
4.Fit caliper and tighten bolts to 95 Nm (70 lbf.ft).
5.Fit road wheel(s) and tighten nuts to 140 Nm
(103 lbf.ft).
6.Remove stand(s) and lower vehicle.

BRAKES
70-38 REPAIRS
Brake pads - front
$% 70.40.02
WARNING: Brake pads must be renewed in axle
sets only, otherwise braking efficiency may be
impaired.
Remove
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 road wheel(s).
3.Remove lower guide pin bolt from caliper and
pivot caliper housing upwards.
4.Remove 2 brake pads from caliper carrier.
Shims are part of the brake pads.Refit
1.Rotate disc by hand and scrape all scale and
rust from around edge of disc.
2.Scrape rust from pad locating surfaces on
caliper.
3.Clean dust from calipers using brake cleaning
fluid.
WARNING: Do not use compressed air to
clean brake components. Dust from friction
materials can be harmful if inhaled.
4.Using tool LRT-70-500, press caliper pistons
fully into bores. Ensure that displaced fluid
does not overflow from reservoir.
5.Fit brake pads with chamfer towards leading
edge of disc.
6.Lower caliper housing over pads.
7.Ensure flats on guide pins locate with lugs on
caliper housing. fit new pivot bolt and tighten to
30 Nm (22 lbf.ft).
8.Fit road wheel(s) and tighten nuts to 140 Nm
(103 lbf.ft).
9.Remove stand(s) and lower vehicle.
10.Depress brake several times to set pad to disc
clearance.
11.Check and top-up brake fluid.

BRAKES
REPAIRS 70-39
Brake pads - rear
$% 70.40.10
WARNING: Brake pads must be renewed in axle
sets only, otherwise braking efficiency may be
impaired.
Remove
1.Raise rear 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 road wheel(s).
3.Remove lower guide pin bolt from caliper and
pivot caliper housing upwards.
4.Remove 2 brake pads from caliper carrier.
Shims are part of the brake pads.Refit
1.Rotate disc by hand and scrape all scale and
rust from around edge of disc.
2.Scrape rust from pad locating surfaces on
caliper.
3.Clean dust from calipers using brake cleaning
fluid.
WARNING: Do not use compressed air to
clean brake components. Dust from friction
materials can be harmful if inhaled.
4.Using tool LRT-70-500, press caliper pistons
fully into bores. Ensure that displaced fluid
does not overflow from reservoir.
5.Fit pads to caliper carrier.
6.Lower caliper housing over pads.
7.Ensure flats on guide pins locate with lugs on
caliper housing. fit new pivot bolt and tighten to
30 Nm (22 lbf.ft).
8.Fit road wheel(s) and tighten nuts to 140 Nm
(103 lbf.ft).
9.Remove stand(s) and lower vehicle.
10.Depress brake several times to set pad to disc
clearance.
11.Check and top-up brake fluid.

BRAKES
REPAIRS 70-45
Housing - caliper - front
$% 70.55.24
Remove
1.Raise front of vehicle, one side.
WARNING: Do not work on or under a
vehicle supported only by a jack. Always
support the vehicle on safety stands.
2.Remove road wheel(s).
3.Clamp brake hose to prevent fluid loss.
4.Remove brake hose banjo bolt and discard
sealing washers.
CAUTION: Always fit plugs to open
connections to prevent contamination.
5.Remove 2 guide pin bolts and remove caliper
housing from carrier.
6.Remove 2 brake pads from caliper carrier. Refit
1.Rotate disc by hand and scrape all scale and
rust from around edge of disc. Clean location
surfaces on caliper bracket.
2.Clean dust from brake parts using brake
cleaning fluid.
WARNING: Do not use compressed air to
clean brake components. Dust from friction
materials can be harmful if inhaled.
3.Fit brake pads to caliper carrier.
4.Position caliper housing to carrier, align flats on
guide pins with caliper housing.
5.Fit guide pin bolts and tighten to 30 Nm (22
lbf.ft).
6.Clean banjo bolt and fit new sealing washers.
7.Position hose to caliper and tighten banjo bolt
to 32 Nm (24 lbf.ft).
8.Remove clamp from brake hose.
9.Bleed brake system.

+ BRAKES, ADJUSTMENTS, Brake
system bleeding.
10.Fit road wheel(s) and tighten nuts to 140 Nm
(103 lbf.ft).
11.Remove stand(s) and lower vehicle.