1998 JAGUAR X308 Workshop Manual

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Page 425 of 2490

JAGUAR X308 1998 2.G Workshop Manual Power Brake Actuatio
n - Brake Boos
ter and Brake Master Cylinder
Re
moval and Installation
Remov

al
• C
AUTIONS:
Replacement of nuts and bolts: Various thread-locking de vices are used on nut

Page 426 of 2490

JAGUAR X308 1998 2.G Workshop Manual In
stallation

11.
Remove brake
booster
from pedal housing.
Remo
ve nut.
Remove brake
booster
from pedal housing.
Remove brake
pedal
from pedal housing.

12 . Remove a

Page 427 of 2490

JAGUAR X308 1998 2.G Workshop Manual Apply grease to
brake pedal pivots.
Position brake pedal.

3. Install brake pedal hou
s
ing to brake booster.
Wh
en installing brake booster,
make sure push-rod locates
inside br

Page 428 of 2490

JAGUAR X308 1998 2.G Workshop Manual
9.
Reconn
ect battery ground cable (IMPORTANT, see operation
86.15.15 for further information).
10. Bleed brake system. Refer to operation 70.25.03.
11. Remove paint-work protection covers

Page 429 of 2490

JAGUAR X308 1998 2.G Workshop Manual Anti-Lock Control -
Lubri
cants, Fluids, Sealants and Adhesives
Torques
Brake Tube, Hoses and Bracket Torques
CAUTI
ON: Replacement of
nuts and bolts: Various thread-locking devices are used on

Page 430 of 2490

JAGUAR X308 1998 2.G Workshop Manual Anti-Lock Control - Anti-Lock Control
Description and Operation

Wheel Spe
ed Sensors
Each
wheel is monitored by a wheel speed se n
sor, to detect the speed of movement of
a toothed gear tha

Page 431 of 2490

JAGUAR X308 1998 2.G Workshop Manual
The brake
control modulator comprises:
a A

BS/TCCM
a h

ydraulic control unit,
an electrically driven hydrau

lic pump,
two low pressure accumulato

rs and damping chambers.

The brake
control modulator comprises:
a A

BS/TCCM
a h

ydraulic control unit,
an electrically driven hydrau

lic pump,
two low pressure accumulato

rs and damping chambers.
ABS/TCCM

The AB
S/TCCM is integrated with the hydrau
lic control unit. It houses the solenoids that operate the hydraulic control unit's
input and return valves; the valve stems locate into the ABS/TCCM's solenoids. There is no electrical connection between
the ABS/TCCM and the hydraulic control unit.
The ABS/TCCM constantly monitors the brake electronic system by passing self-checking electrical pulses around the circuit.
The self check procedures carried-out by the ABS/TCCM are listed below:
1. 1. Monitoring of the operating voltage: the control mo dule will shut-down should the voltages not be
(approximately) in the range of 9 to 19V.
2. 2. The pump is monitored for volt age supply and voltage feedback.
3. 3. Monitoring for disturbance, where a failure may be caus ed by external radio frequency interference, internal
leakage current, defective valve transistor or a faulty valve.
4. 4. Internal controller failure, de tected by a RAM and ROM test.
5. 5. The controller area network (CAN) micr o-controller checks for correct operation of the communication network
and performs a RAM self-check.
CAUTION: Disconnection of ABS/TCCM connectors may introduce other fault codes. Following rectification and
reconnection, ensure that no induced codes exist.
5.
Signals processed by the ABS/TCCM are also sent to the CAN for vehicle use, such as the instrument cluster speed display,
cruise control and stability/traction control.
Hydraulic Control Unit

Control of
the fluid pressure to
the front and rear brakes is by means of the valves contained in the hydraulic control unit.
The valves are operated by solenoids housed in the ABS/TCCM.
Hydraulic Pump
The
hydraulic pump is integrated
with the hydraulic control unit.

Bra
ke Control Modulator

Page 432 of 2490

JAGUAR X308 1998 2.G Workshop Manual It is a reciprocating two
-circuit pu
mp in which one brake circuit is as signed to each pump circuit.
It supplies th
e fluid pressure and vo
lume to supply the brake circuits under ABS and

It is a reciprocating two
-circuit pu
mp in which one brake circuit is as signed to each pump circuit.
It supplies th
e fluid pressure and vo
lume to supply the brake circuits under ABS and Traction control.
The pump is driven by an electri
c motor, with the pump
housing incorporating two lo w pressure accumulators and
damping chambers for each brake circuit.
The ac cu
mulator stores the pressure and smooths out the output pu
lses from the pump.
ABS Warning Lamp
The sys
tem will be set in a fail-safe mode if a problem is de
tected; a warning lamp on the instrument panel will notify the
driver there is a problem.
Anti-Lock Braking Sy
stem (ABS)
The AB
S components are combined with
an hydraulic booster and a tandem master cylinder to provide a two circuit braking
system. The system comprises, four wheel speed sensor s, a brake control modulator and an ABS warning lamp.
Should a wheel start to lock-up during braking a signal tr ansmitted from the wheel speed sensor to the brake control
modulator will start the hydraulic pump. The brake control modula tor will close the input valve of the line connected to the
locked-wheel to stop any increase in fluid pressure to the br ake caliper. If this fails to prevent the wheel locking, the
pressure in the caliper will be decreased by opening the return valve until th e wheel starts accelerating again. The fluid
pressure from the return va lve is directed into the low pressure accumulator, housed in the pump.
From the low pressure accumulator, fl uid is pumped through the damping cham ber to the brake master cylinder. The
pressure to the brake caliper will then be increased in small steps to maintain maximum adhesion between the tire and road
surface. This is achieved by closing the return valve, and opening the input valve and using the hydraulic pump to increase
the pressure.
Although the system senses all four wheels independently, the rear wheels are regulated as a pair. If a sensor on a rear
wheel detects a wheel decelerating rapidly, then the fluid pressure to both wheels is reduced. The fluid pressure is then
dictated by the wheel having the lowe st adhesion with the road surface.
The ABS system will be set in a fail-safe mode if a problem is detected; a warn ing lamp on the instrument panel will notify
the driver there is a problem. The brake system will still operate conventionally and with the same standard of performance
as a vehicle not equipped with ABS.
Automa tic Stability Control (ASC)

Th
e ASC utilizes the ABS sensing arrangement to provide the maximum traction force to propel the vehicle.
The ASC is switched on when the engine is started. The system can be switched off by pressing the 'ASC OFF' (the switched
is marked 'TRAC OFF' on vehicles fitted with traction control). The switch, which is situated in the center console switchpack,
lights up to warn that the system is sw itched off. An 'ASC' amber warning light flashes on the instrument panel when the
system detects a spinning wheel.
The ASC system uses engine intervention to reduce the torque delivered to the drive wheels to prevent them spinning.
Engine torque is re duced in three ways:
The
throttle is moved towards the closed position.
The ignition is retarded. F
u
el is cut-off at the cylinder injectors.
Wheel spin is detected by the wheel sp eed sensors and communicated to the AB S/TCCM. The ABS/TCCM uses information
from the controller area network (CAN) to calculate the torque that the engine should produce to stop the wheel spinning.
Torque reductions are then requested from the engine control module (ECM ) through the CAN. The throttle is then
positioned to provide the target torque, which has been calculated to prevent wheel spin. During the transient phase of
torque reduction the fuel is cut-off and th e ignition retarded Both the fuel cut-off an d ignition retard will be restored to
normal when the throttle is set to its new position.
The ASC uses a brake control modulator with six solenoid va lves: three normally open inlet valves and three normally

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