1994 JAGUAR XJ6 wheel

Brakes
The pressure at the inlet valves corresponds to the opening pressure of the relief valve (item 15) incorporated in the
isolation valve. Excess brake fluid is drained to the suction side of the pump via the relief valve and returns either to
the TMC secondary circuit and on to the
fluid reservoir, or is directly drawn on by the pump.
As soon as the spinning wheel has been braked down into the normal range of wheel spin, the NO valves (items
16 or 17) close to prevent any further increase in brake pressure. Depending upon the acceleration of the wheel, the NC
valve (item
20 or 21) may open to decrease thesecondary circuit brake pressure. NCvalves (item 17 or 18) may remain
closed in orderto achieve a brake pressure holding phase. If the pressure in the secondarycircuit needs to be increased
again, the NC valve closes again (if open) and the NO valve opens, diverting the necessary volume flow. This control
action, keeps the wheel in the range of optimum slip until the spinning tendency ceases.
The NO isolation valve
(14) remains closed throughout the traction control cycle.
An actuation of the brake, sensed by the control module, causes the traction control mode to be terminated and the
isolation valve (item
14) to be opened. The TMC pressure simultaneously closes the hydraulic inlet valve (item 13) so that the pump can no longer draw fluid from it. The ABS / TC CM now operates in normal ABS mode.
m: When traction control is initiated, speed control is deactivated (if in operation) and requires re-setting after
the traction control mode has terminated. Gear shift is inhibited on automatic transmission vehicles; no down- shifts are allowed and upshifts occur at 4800 RPM.
X300 VSM 15 Issue 1 August 1994

12.2 FAULT DIAGNOSIS AND TESTING
rrouble
-ong brake pedal
dibration during braking
'oor braking performance
3rakes pull to one side
3rakes do not release
ixcessive pedal travel
Cause
Brake caliper piston or caliper guide
pins sticking
Worn
I damaged brake pads
Worn
1 damaged brake pads
Loose caliper mounting bolts
Insufficient grease on sliding parts
Foreign material
or scratches on
brake rotor contact surface
Damaged brake rotor contact surface
Leak
in hydraulic system
Air
in system
Worn
I damaged brake pads
Foreign material on brake pads
Brake caliper piston malfunction
Tandem master cylinder malfunction
Vacuum booster fault
Disconnected
or damaged vacuum
hose
Low brake
fluid level
Worn
I damaged brake pads
Foreign material on brake pad
Failing valves
in ABS valve block
Abnormal wear or distortion on front
brake rotor
Incorrect wheel alignment
Incorrect tire pressure
No brake pedal free play
Vacuum booster
binding
Tandem master cylinder return port faulty
Faulty valve
in ABS valve block
Leak
in hydraulic system
Air
in system
Remedy
Service or renew caliper or caliper
guide pins
Renew brake pads
Renew brake pads
Tighten caliper mounting bolts
Apply grease where necessary
Clean brake rotor contact surface
Renew brake
rotor
Repair leak. Check all pipework con-
nections. Refill and bleed the system
Check the system
for leaks and bleed
brakes
Renew brake pads
Examine brake pads and clean
or
renew as necessary
Renew faulty brake caliper piston
Service
or renew tandem master cyl- inder
Renew vacuum booster
Renew vacuum hose
Check for leaks, refill and bleed the
system
Renew brake pads
Examine brake pads and clean
or renew as necessary
Renew valve block
Examine front brake
rotor and service
or renew as necessary
Carry out wheel alignment. Refer to
Section
11, iv Service Data
Inflate tire
to correct pressure
Adjust brake pedal free play
Renew vacuum booster
Clean return
port on tandem master cy I i nder
Renew valve block
Repair leak. Check all pipework con
- nections. Refill and bleed the system
Check the system
for leaks and bleed
brakes
0
0
0
Issue 1 August 1994 16 X300 VSM

12.2 (continued)
rrouble
Excessive pedal travel (Cont'd)
Brakes grab
Brakes drag
Hard brake pedal when pressed
Excessive brake noise
Cause
Worn tandem master cylinder piston
seals or scored cylinder bore
'knock back'. Excessive brake rotor
run
-out or loose wheel bearings
Brake pads contaminated by grease
or brake fluid
Brake pads distorted, cracked or
loose
Loose caliper mounting bolts or
guide pins
Seized or incorrectly adjusted parking
brake or cable
Broken or weak parking brake return
springs
Caliper pistons seized
Brake pedal binding
at pivot points
Vacuum booster binding
Tandem master cylinder faulty
Lack of vacuum
at the vacuum
booster
Tandem master cylinder
pushrod
binding
Frozen tandem master cylinder pis
-
ton
Brake caliper piston or caliper guide
pins seized
Worn brake pads
Bent or cracked parking brake shoes
Foreign objects in brake pads or
park- ing brake shoes
Broken
/ loose parking brake hold
down springs or return springs
Loose caliper mounting bolts
Remedy
Renew tandem master cylinder
Check brake rotor run
-out and renew
as necessary. Adjust wheel bearing
Renew brake pads. Check
pipework for leaks
Renew brake pads
Check caliper and repair
/ renew as
necessary
Examine parking brake and repair
/
renew as necessary
Renew parking brake return springs
Examine calipers and repair
/ renew
as necessary
Examine brake pedal bushings and
repair
/ renew as necessary
Renew vacuum booster
Examine tandem master cylinder and
repair
/ renew as necessary
Check vacuum hose. Repair or renew
as necessary
Renew tandem master cylinder
Renew tandem master cylinder
Examine caliper and renew/ repair as
necessary
Renew brake pads
Renew parking brake shoes
Examine brake pads and and parking
brake shoes. Clean or renew as
necessary
Examine parking brake assembly.
Re- pair or renew as necessary
Re
-torque caliper mounting bolts

12.6 REAR WHEEL SPEED SENSOR - RENEW
SRO
70.60.04
. Drive the vehicle onto a ramp or raise the back and support
on two stands.
. Cut and remove the ratchet strap securing the speed sen- sor harness to the brake hose.
. Undo and remove the speed sensor to hub carrier secur- ing bolt (Fig. 1).
Remove the speed sensor from the hub carrier and allow
it to hang free, forward of the 'A' frame.
Open both rear doors and displace the rear seat cushion
from the seat pan brackets. Reposition the rear seat
cushion forwards.
9 Push the seat belts/ buckles through the seat cushion slots
and remove the rear seat cushion from the vehicle.
. Displace the RH side of the seat pan sound proofing (1 Fig. 2) to gain access to the speed sensor harness (2 Fig. 2).
9 Displace the speed sensor harness grommet (3 Fig. 2) from the seat pan aperture.
. Feed the speed sensor harness through the seat pan aper- ture and disconnect the multi-plug (4 Fig. 2).
9 Position the new speed sensor harness and connect the
multi-plug.
. Feed the speed sensor harness through the seat pan aper- ture to hang free below the vehicle.
. Refit and fully seat the speed sensor harness grommet to
the seat pan aperture.
Reposition theseat pan sound proofing to its original posi- tion.
Position the rear seat cushion and feed the seat belt / buckles through the slots.
Locate the rear seat cushion into the seat pan brackets (5 Fig. 2).
. Stow the seat belts / buckles.
. Position the speed sensor harness rearwards over the 'A'
Fit and tighten the speed sensor to hub carrier securing
Secure the speed sensor harness to the brake hose using
frame
and locate into the hub carrier.
bolt.
a ratchet strap. Trim the ratchet strap. Fig.
1
Fig. 2
Issue 1 August 1994 22 X300 VSM
0
0
0

Brakes
12.7 HYDRAULICCONTROL MODULE- RENEW
SRO 70.60.18
70.60.1
9
Refer to Section 12.4, Brake System Bleeding before carrying out this procedure. Pay particular attention to the warn- ings and cautions relating to brake fluid, cleanliness and cleaning materials.
W: The illustration shows the hydraulic control module of a 6 cyl. vehicle with traction control. Hydraulic control
modules on non-traction control vehicles have only three outlet ports. Apart from this, the removal procedure
is the same for all vehicles.
. Raise the vehicle.
Displace the bleeder screw dust cap of the front LH caliper.
The dust cap will remain captive
on the bleed screw.
. Connect a bleeder tube and bottle to the bleeder screw (1
Fig. 1) and open the bleeder screw.
. Fit a brake pedal hold-down tool (JDS-9013) between the
brake pedal and the steering wheel. Adjust the tool to op
- erate the brake pedal 60mm down. This operation is
necessary to prevent fluid loss from the reservoirthrough
. Re-tighten the front LH caliper bleeder screw. Disconnect
the bleeder tube from the bleeder screw and remove the
tube and bottle. Refit the bleeder screw dust cap.
Undo the securing bolt of the multi-plug connector (1 Fig. 2). The bolt will remain captive. Disconnect the multi-plug
connector and reposition safely.
. Place absorbent material underneath the hydraulic con-
trol module to absorb any spillages.
Undo the tandem master cylinder CTMC) brake pipe gland
nuts (2 Fig.2) and disconnect the brake pipes.
. Fit plugs immediately to the brake pipes and the hydraulic
control module to prevent fluid
loss.
. Undo the rear brake pipe gland nuts (3 Fig. 2) at the pres- sure conscious reducing valves (PCRVs) (4 Fig. 2). Remove
the rear brake pipes.
disconnected brake pipes.
Note: Take necessary steps to prevent rotation of the
PCRVs when removing the rear brake pipes.
Fit plugs immediately to the brake pipes and the PCRVs to
. Undo and remove the PCRVs. Fit plugs immediately to the
Place PCRVs aside to be fitted later to the new hydraulic
. Undo the front brake pipe gland nuts (5 Fig. 2) and remove
. Fit plugs immediately to the brake pipes and the hydraulic
. Undo and remove the three securing nuts (6 Fig. 2) and re-
0 prevent fluid loss.
PCRVs and the hydraulic control module.
control module.
the front brake pipes.
control module to prevent fluid
loss.
move the hydraulic control module. Fia.
1
3 1 J70 296
Fia. 2
Issue 1 August 1994 X300 VSM 23

Brakes
12.8
SRO 70.60.21
PRESSURE CONSCIOUS REDUCING VALVES - RENEW
Refer to Section 12.4, Brake System Bleeding before carrying out this procedure. Pay particular attention to the warn- ings and cautions relating to brake fluid, cleanliness and cleaning materials.
Note: The illustration shows the hydraulic control module of a 6 cyl. vehicle with traction control. Hydraulic control
modules on non-traction control vehicles have only three outlet ports. Apart from this, the removal procedure
is the same for all vehicles.
. Raise the vehicle.
Displace the bleeder screw dust cap of the front LH caliper.
The dust cap will remain captive on the bleed screw.
rn Connect a bleeder tube and bottle to the bleeder screw (1 Fig. 1) and open the bleeder screw.
Fit a brake pedal hold-down tool (JDS-9013) between the
brake pedal and the steering wheel. Adjust the tool to op- erate the brake pedal 60mm down. This operation is
necessary to prevent fluid
loss from the reservoir through
disconnected brake pipes.
. Re-tighten the front LH caliper bleeder screw. Disconnect
the bleeder tube from the bleeder screw and remove the
tube and bottle. Refit the bleeder screw dust cap.
rn Place absorbent material underneath the hydraulic con- trol module to absorb any spillages.
. Undo the rear brake pipe gland nuts (1 Fig. 2) at the pres- sure conscious reducing valves (PCRVs) (2 Fig. 2). Remove
the rear brake pipes.
m: Take necessary steps to prevent rotation of the
PCRVs when removing the rear brake pipes.
Fit plugs immediately to the brake pipes and the PCRVs to
Undo and remove the PCRVs. Fit plugs immediately to the
. Clean the surrounding area.
. Fit new PCRVs to the hydraulic control module, removing
plugs immediately priorto connection. Tighten the PCRVs.
. Connect the rear hydraulic brake pipes to the PCRVs, re- moving the plugs immediately prior to connection.
Tighten the gland nuts.
prevent
fluid loss.
PCRVs
and the hydraulic control module.
0
Note: Take necessary steps to prevent rotation of the
PCRVs when fitting the rear brake pipes.
. Removethe absorbent material and clean the surrounding
. Ensure that all fixings are torque tightened to specified tol-
Release the brake pedal hold-down tool and remove.
. Bleed the brake system (refer to sub-section 12.4.4).
. Examine the hydraulic control module for leaks.
area.
erances. Fia.
1
Fia. 2
X300 VSM 25 Issue 1 August 1994

Body Components & Trim ~
issue 1 August 1994 X300 VSM 21
13.3.17 Fascia Board, Renew
SRO 76.46.01
. Remove
the battery cover and disconnect the battery.
Remove the drivers side and passenger side underscuttle
pads, see sub
-sections 13.3.19 and 13.3.20.
. Remove the drivers airbag module, see section 15.5.
Remove the steering wheel, section 10.
Remove the drivers side and passenger side fascia closing
. Remove the fascia center veneer panel, see subsection
Remove the fascia board for access, see subsection
. Disconnect the air conditioning differential potentiometer
Remove the differential potentiometer assembly.
. Displace and reposition the through panel connectors
from the fascia assembly.
. Displace the fascia vent motor / gearbox assemblies har- ness multi-plug from the mounting bracket.
. Disconnect and reposition the fascia harness to console
harness
multi-plug from the mounting bracket.
. Disconnect the BPU harness multi-plugs.
Remove the tiestraps securing the harness to the fascia.
. Reposition the fascia on a bench.
= Displace and reposition the solar sensor assembly from
Disconnect the solar sensor harness multi-plug.
Remove the solar sensor assembly.
= Undo and remove the defrost vents securing screws.
Displace and reposition the defrost vent assemblies.
. Disconnect the tweeter speaker harness multi-plugs.
. Remove the defrost vent assemblies.
. Displace the fascia harness grommet from the fascia.
. Route the harness through the aperture.
Remove the fascia harness assembly.
. Undo and remove passenger airbag deployment door to
fascia securing bolts ( one bolt is removed with the fascia).
. Displace and remove the deployment door assembly.
. Undo and remove the passenger airbag module to fascia
. Displace and remove the airbag module assembly.
. Undo and remove the airbag module I BPU mounting
bracket assembly to fascia securing nuts 1 bolts.
= Displace and remove the mounting bracket assembly.
. Retrieve the spacing washers.
. Displace and remove the side vent outlets from the fascia.
. Displace and remove the side vent ducts securing clips.
. Displace and remove the side vent ducts.
. Undo and remove the center vent flap assembly to fascia
. Displace and remove the center vent flap assembly.
Undo and remove fascia location bracket securing nuts.
Displace and remove the location bracket.
panels, see
sub
-sections 13.3.22 and 13.3.21.
13.3.23. 13.3.17.
harness multi
-plug.
the fascia.
securing bolts.
securing nuts.

Body Components & Trim
. Reposition and fit the motor/gearbox assemblies harness
. Fully seat the through panel connectors to the fascia.
. Place the air conditioning differential potentiometer to the
fascia and route the differential potentiometer harness
through the vent aperture.
. Reconnect the differential potentiometer harness multi-
Plug.
Refit the fascia board.
. Refit the center veneer panel.
. Refit the fascia closing panels.
. Refit the steering wheel.
. Refit the drivers airbag module.
. Refit the underscuttle pads.
. Reconnect the battery and refit the battery cover.
multi
-plug
to the mounting bracket.
X300 VSM 23 Issue 1 August 1994