VIN JAGUAR XJ6 1997 2.G Repair Manual

e) The silicone boot must be installed in the
correct position to prevent the boot from
being melted and to allow the sensor to
operate properly.
Check
13Locate the oxygen sensor electrical
connector and inspect the oxygen sensor
heater. Disconnect the oxygen sensor
electrical connector and connect an
ohmmeter between the two terminals (see
illustration). It should be around 5 to 6 ohms.
14Also, check for proper supply voltage to
the oxygen sensor heater. Measure the voltage
with the electrical connector connected. Insert
a long pin into the backside of the electrical
connector on the correct wire. With the ignition
key ON (engine not running), check for voltage.
There should be approximately 12 volts.
Note:Battery voltage to the heater is supplied
by the main relay (1988 to 1990) or the oxygen
sensor relay (1991 to 1994). Check the
oxygen sensor relay and the wiring harness if
battery voltage is not available to the heater.
Refer to the wiring diagrams at the end of
Chapter 12 and the relay locator schematics
also in Chapter 12.
15Next, check for a millivolt signal from the
oxygen sensor. Locate the oxygen sensor
electrical connector and insert a long pin into
the oxygen sensor signal wire terminal (see
illustration). The SIGNAL wire is the single wire
with the rubber sheath covering its terminal.
16Monitor the voltage signal (millivolts) as
the engine goes from cold to warm.
17The oxygen sensor will produce a steady
voltage signal at first (open loop) of
approximately 0.1 to 0.2 volts with the engine
cold. After a period of approximately two
minutes, the engine will reach operating
temperature and the oxygen sensor will startto fluctuate between 0.1 to 0.9 volts (closed
loop). If the oxygen sensor fails to reach the
closed loop mode or there is a very long
period of time until it does switch into closed
loop mode, or if the voltage doesn’t fluctuate
well (indicating a “lazy” sensor), renew the
oxygen sensor with a new part.
Renewal
Note:Because it is installed in the exhaust
manifold or pipe, which contracts when cool,
the oxygen sensor may be very difficult to
loosen when the engine is cold. Rather than
risk damage to the sensor (assuming you are
planning to reuse it in another manifold or
pipe), start and run the engine for a minute or
two, then shut it off. Be careful not to burn
yourself during the following procedure.
18Disconnect the cable from the negative
terminal of the battery.
Caution: If the stereo in your vehicle is
equipped with an anti-theft system, make
sure you have the correct activation code
before disconnecting the battery.
19Raise the vehicle and place it securely on
axle stands.
20Disconnect the electrical connectors from
the sensor pigtail lead.
21Unscrew the oxygen sensor from the
exhaust system (see illustration).
Caution: Excessive force may damage the
threads.
22Anti-seize compound must be used on
the threads of the sensor to facilitate future
removal. The threads of new sensors will
already be coated with this compound, but if
an old sensor is removed and reinstalled,
recoat the threads.
23Refit the sensor and tighten it securely.
24Reconnect the electrical connectors to
the main engine wiring harness.25Lower the vehicle and reconnect the cable
to the negative terminal of the battery.
Throttle potentiometer
General description
26The throttle potentiometer is located on
the end of the throttle shaft on the bottom
section of the throttle body. By monitoring the
output voltage from the throttle
potentiometer, the ECU can alter fuel delivery
based on throttle valve angle (driver demand).
A broken or loose throttle potentiometer will
cause bursts of fuel from the injectors and an
unstable idle because the ECU thinks the
throttle is moving. Throttle body removal
procedures are covered in Chapter 4.
Check
27Check for the proper reference voltage to
the throttle potentiometer. Carefully back-
probe the throttle potentiometer electrical
connector using a pin on the reference voltage
wire and ground (see illustration). With the
ignition key ON (engine not running) the
reference voltage should be about 5.0 volts.
Emissions and engine control systems 6•5
6
4.21 Unscrew the oxygen sensor from the
exhaust system
3261 Jaguar XJ6 4.13 To test the oxygen sensor heater, disconnect the electrical
connector, and working on the sensor side, check the resistance
across the two terminals. Heater resistance should be 5 to 6 ohms
4.15 Refit a pin into the backside of the oxygen sensor connector
into the correct terminal and check for a millivolt output signal
generated by the sensor as it warms up. The SIGNAL wire is easily
recognised by the rubber sheath covering the terminal (arrowed)

42Also, check the reference voltage to the
MAF sensor from the computer. Backprobe
terminal number 6 and make sure that
approximately 5 volts is present.
Renewal
43Disconnect the electrical connector from
the MAF sensor.
44Remove the air cleaner assembly (see
Chapter 4).
45Remove the four bolts and separate the
MAF sensor from the air intake duct.
46Refitting is the reverse of removal.
Intake air temperature
(IAT) sensor
General description
47The intake air temperature sensor is
located inside the air intake duct. This sensor
acts as a resistor which changes value
according to the temperature of the air entering
the engine. Low temperatures produce a high
resistance value (for example, at 68° F the
value is 2.0 to 2.6 k-ohms) while high
temperatures produce low resistance values (at
176° F the resistance is 260 to 330 ohms. The
ECU supplies around 5 volts (reference
voltage) to the air temperature sensor.
The voltage will change according to the
temperature of the incoming air. The voltage
will be high when the air temperature is cold
and low when the air temperature is warm. Any
problems with the air temperature sensor
will usually set a code 8 (1988 and 1989) or
code 16 (1990 to 1994).
Check
48To check the air temperature sensor,
disconnect the two prong electrical connector
and turn the ignition key ON but do not start
the engine.
49Measure the voltage (reference voltage),
which should be approximately 5 volts.
50If the voltage signal is not correct, havethe ECU diagnosed by a dealer service
department or other repair workshop.
51Measure the resistance across the air
temperature sensor terminals (see illustration).
The resistance should be HIGH when the air
temperature is LOW. Next, start the engine and
let it idle. Wait awhile and let the engine reach
operating temperature. Turn the ignition OFF,
disconnect the air temperature sensor and
measure the resistance across the terminals.
The resistance should be LOW when the air
temperature is HIGH. If the sensor does not
exhibit this change in resistance, renew it with a
new part.
EGR gas temperature sensor
(1991 to 1994 models)
General description
52The EGR gas temperature sensor is
mounted in the exhaust gas transfer pipe. This
sensor detects the temperature of the exhaust
moving through the EGR valve. The information
is sent to the ECU so the EGR on/off time is
regulated precisely and efficiently.
Check
53Disconnect the harness connector for the
EGR gas temperature sensor and measure
the resistance of the sensor at the various
temperatures. Refer to the Specifications
listed in this Chapter for a list of the
temperatures and the resistance values.
Removal and refitting
54Disconnect the harness connector for the
EGR gas temperature sensor and using an
open-end spanner, remove the sensor from
the EGR adapter under the intake manifold.
55Refitting is the reverse of removal.
Speed sensor
General description
56The speed sensor is mounted on thedifferential housing and monitors vehicle
speed by sensing the rotational speed of the
rear axle. A problem with this sensor or circuit
will set a code 68 and may also be the cause
of an inoperative speedometer. If the
speedometer doesn’t work, the problem lies
in the speed sensor, the instrument cluster,
the ECU or the wiring in between. For further
diagnosis, take the vehicle to a dealer service
department or other suitably-equipped and
qualified repair workshop.
Crankshaft position sensor
57The crankshaft position sensor is located
in the front timing cover near the crankshaft
pulley (see illustration). The crankshaft
position sensor relays a signal to the ECU to
indicate the exact position (angle) of the
crankshaft.
Check
58The crankshaft sensor cannot be
diagnosed without the proper tools. The
Jaguar dealer uses a diagnostic scope/
computer called the JDS. Have the crankshaft
sensor diagnosed by the dealer service
department or other qualified repair workshop.
Renewal
59To renew the sensor, disconnect the
electrical connector and remove the bolt from
the crankshaft position sensor. Refitting is the
reverse of removal.
60To renew the crankshaft sensor gear,
remove the front pulley (refer to Chapter 2A).
61Be sure there is a small gap between the
crankshaft sensor and the teeth on the gear. It
should be between 0.46 to 1.07 mm (0.018 to
0.042 inch).
62Refitting is the reverse of removal. Tighten
the crankshaft sensor bolt to the torque listed
in this Chapter’s Specifications.
Emissions and engine control systems 6•7
6
3261 Jaguar XJ6 4.51 The air intake temperature sensor resistance will DECREASE
when the temperature of the air INCREASES
4.57 Location of the crankshaft position sensor

5 Air Injector Reactor
(AIR) system
General information
1The air injection reactor system reduces
carbon monoxide and hydrocarbon content
in the exhaust gases by injecting fresh air into
the hot exhaust gases leaving the exhaust
ports. When fresh air is mixed with hot
exhaust gases, oxidation is increased,
reducing the concentration of hydrocarbons
and carbon monoxide and converting them
into harmless carbon dioxide and water.
2The air injection system is composed of an
air pump, diverter valve (bypass), check valve,
air injection manifold, vacuum delay valve,
vacuum control solenoid, air pump magnetic
clutch, air pump clutch relay and hoses (see
illustration). The air pump is driven by a belt
from the crankshaft and supplies compressed
air to the exhaust manifold(s). The check valve
prevents the reverse flow of exhaust gases into
the system. The vacuum-operated (early
models) or electrically-operated (later models)air cut-off valve prevents air from being drawn
into the exhaust when the air pump is switched
off. System vacuum to the air cut-off valve is
controlled by the solenoid vacuum valve in
parallel circuit with the air pump. A delay valve
prevents vacuum loss to the solenoid valve
during wide open throttle operation.
3Injected air is controlled by the computer,
the air pump clutch and the air pump clutch
relay. The AIR system is used during warm-up
(58 to 83° F) to control emissions while the
engine is running rich. The oxygen sensor
feedback system cannot function while the AIR
system is operating. The computer controls
both systems during warm-up and operating
temperatures. If problems occur with the
AIR system relay or circuit, the on-board
diagnosis system will set a code 66.
Check
4Check the condition of the air pump
drivebelt, the injection hoses and the injection
manifold. Make sure that all components are
intact and there are no leaks.
5Check the operation of the air pump clutch
relay (see illustration)and the air pump
clutch. First remove the relay and check forbattery voltage to the relay. Also, check the
relay itself. Refer to the relay checking
procedure in Chapter 12. Extract codes from
the self-diagnosis system (see Section 3) and
check for a code 66, AIR relay malfunction.
6Make sure the electrical connector is
securely fastened to the diverter valve (see
illustration). If everything appears OK but a
fault code still sets, have the system
diagnosed by a dealer service department or
other qualified repair workshop.
Air pump renewal
7Disconnect the cable from the negative
terminal of the battery.
Caution: If the stereo in your vehicle is
equipped with an anti-theft system, make
sure you have the correct activation code
before disconnecting the battery.
8Disconnect the electrical connector from
the air pump clutch.
9Loosen the clips from the air inlet and outlet
hose and separate them from the air injection
pump.
10Loosen the adjuster and pivot bolts (see
illustration)and nuts but do not remove them
from the air injection pump brackets.
6•8 Emissions and engine control systems
3261 Jaguar XJ6 5.2 Schematic of the Air Injection Reactor (AIR) system
5.6 Location of the AIR diverter valve on a 1992 model - check the
hoses for cracking and the electrical connector for security5.10 Loosen the pivot bolt and then the adjustment nut to remove
the drivebelt from the air pump. The adjustment nut has a lock bolt
that must be loosened before the pump will move down the adjuster
5.5 Location of the AIR pump relay on a 1992 model

11Swing the pump toward the engine and
remove the drivebelt from the pump.
12Remove the link arm through-bolt.
13Remove the pivot bolt and front spacer,
rear cone and air injection pump from the
engine compartment.
14Remove the nut securing the front pulley
on the air injection pump.
15Remove the clutch snap-ring and the
clutch.
16Refitting is the reverse of removal.
6 Exhaust Gas Recirculation
(EGR) system
Note 1: Some 1990 models have the EGR
vacuum hose routed incorrectly through the
bulkhead securing straps, thereby restricting
the vacuum signal to the EGR valve. Remove
the EGR vacuum hose from the bulkhead
harness and refit a new hose. Secure it to the
engine compartment using tie-wraps and do
not allow any restrictions in the hose.Note 2: Some models have copper sealing
washers that soften and leak around the EGR
valve causing engine performance and
starting problems. Refit steel washers and
pipe adapters into the EGR system. Contact a
Jaguar dealer for the VIN numbers and years
of the models that are affected by this defect.
1To reduce oxides of nitrogen emissions,
some of the exhaust gases are recirculated
through the EGR valve to the intake manifold
to lower combustion temperatures.
2The EGR system consists of the EGR valve,
an EGR solenoid, an EGR gas temperature
sensor and the transfer pipe (see illustration).
Check
EGR valve
3Start the engine and allow it to idle.
4Detach the vacuum hose from the EGR
valve and attach a hand vacuum pump in its
place (see illustration).
5Apply vacuum to the EGR valve. Vacuum
should remain steady and the engine should
run poorly. Note:This action will raise the
pintle and allow exhaust gases to recirculateinto the intake system and cause rough
running condition at idle.Double-check the
movement of the pintle by checking the
diaphragm using the tip of your finger (see
illustration). If the EGR diaphragm moves
smoothly and holds steady when vacuum is
applied, the EGR valve is working properly.
Warning: Don’t burn yourself. If
the EGR valve is hot, wear a
glove or wait until it cools.
a) If the vacuum doesn’t remain steady and
the engine doesn’t run poorly, renew the
EGR valve and recheck it.
b) If the vacuum remains steady but the
engine doesn’t run poorly, remove the
EGR valve and check the valve and the
intake manifold for blockage. Clean or
renew parts as necessary and recheck.EGR system
6Disconnect the hose from the EGR valve,
refit a vacuum gauge and check for vacuum
to the EGR valve. There should be vacuum
present with the engine warmed to operating
temperature (above 140° F) and between
1000 and 4000 rpm (see illustration).
Emissions and engine control systems 6•9
6
3261 Jaguar XJ6 6.2 Schematic of the EGR system
6.4 Apply vacuum to the EGR valve and confirm that the valve
opens and allows exhaust gases to circulate. Once it is activated,
the EGR valve should hold steady (no loss in vacuum)
6.5 Use a fingertip to move the diaphragm inside the EGR valve6.6 Check for vacuum to the EGR valve from the throttle body

3261 Jaguar XJ6
9
Chapter 9
Braking system
General
Brake fluid type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 1
Minimum brake pad thickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 1
Brake disc minimum permissible thickness . . . . . . . . . . . . . . . . . . . . . . Cast into disc
Parallelism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.013 mm (0.0005 inch) maximum
Runout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.102 mm (0.004 inch) maximum
Torque wrench settingsNm lbf ft
Brake servo mounting nuts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 7
Caliper bolts (front and rear) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 to 40 23 to 29
Caliper bracket bolts
Front bracket . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 to 128 75 to 94
Rear bracket . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 to 62 40 to 45
Master cylinder-to-brake servo nuts . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 to 28 16 to 20
Wheel nuts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 1 Specifications Anti-lock Brake System (ABS) - general information . . . . . . . . . . . . . 2
Brake check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 1
Brake disc - inspection, removal and refitting . . . . . . . . . . . . . . . . . . 5
Brake fluid level check . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 1
Brake hoses and lines - inspection and renewal . . . . . . . . . . . . . . . . 8
Brake hydraulic system - bleeding . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Brake light switch - check and renewal . . . . . . . . . . . . . . . . . . . . . . . 13
Brake servo - general information, removal and refitting . . . . . . . . . 7Disc brake caliper - removal, overhaul and refitting . . . . . . . . . . . . . 4
Disc brake pads - renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
General information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Handbrake cable - adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Handbrake cables - renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Handbrake shoes - check and renewal . . . . . . . . . . . . . . . . . . . . . . 12
Master cylinder - removal, overhaul and refitting . . . . . . . . . . . . . . . 6
9•1
Specifications Contents
Easy,suitable for
novice with little
experienceFairly easy,suitable
for beginner with
some experienceFairly difficult,
suitable for competent
DIY mechanic
Difficult,suitable for
experienced DIY
mechanicVery difficult,
suitable for expert DIY
or professional
Degrees of difficulty
54321
1 General information
All models covered by this manual are
equipped with hydraulically operated front
and rear disc brake systems. Both front and
rear brakes are self adjusting.
Hydraulic system
The hydraulic system is divided into
two separate circuits. The master cylinder has
separate reservoirs for the two circuits, and, in
the event of a leak or failure in one hydraulic
circuit, the other circuit will remain operative.
All models are equipped with an Anti-lock
Braking System (ABS).
Brake servo
A hydraulic brake servo system is used on
all models covered by this manual. Thissystem uses hydraulic pressure from an
engine-driven pump on models equipped with
a power hydraulic system, and an electric
pump on models without the power hydraulic
system.
Handbrake
The handbrake lever operates the rear
brakes through cable actuation. It’s activated
by a lever mounted in the centre console. The
handbrake assembly uses a pair of brake
shoes located inside the rear hub/brake disc.
Brake pad wear warning system
The brake pad wear warning system turns
on a red light in the instrument cluster when
the brake pads have worn down to the point
at which they must be replaced. Do NOT
ignore this reminder. If you don’t renew the
pads shortly after the brake pad wear warning
light comes on, the brake discs will be
damaged.The wear sensors are attached to the brake
pads. Once the pads wear down to the point
at which they’re flush with the sensor, the disc
grinds away the side of the sensor facing the
disc, the wire inside the sensor is broken, the
circuit is opened and the red light on the
instrument panel comes on.
Always check the sensor(s) when replacing
the pads. If you change the pads before the
warning light comes on, the sensor(s) may still
be good; once the light has come on, renew
the sensor.
Service
After completing any operation involving
dismantling of any part of the brake system,
always test drive the vehicle to check for
proper braking performance before resuming
normal driving. When testing the brakes,
perform the tests on a clean, dry, flat surface.
Conditions other than these can lead to
inaccurate test results.

6Be sure to buy new pads with wear
sensors. Pattern pads may not have wear
sensors; refitting pads without wear sensors
will cause the dash warning light to come on.
7To refit the new pads, reverse the removal
procedure. When refitting the caliper, be sure
to tighten the mounting bolts to the torque
listed in this Chapter’s Specifications.
8After the job is completed, depress the
brake pedal a few times to bring the pads into
contact with the discs. The pedal should be at
normal height above the floorpan and firm.
Check the brake fluid level and add enough to
top it up (see Chapter 1). Inspect carefully for
leaks and check the operation of the brakes
before placing the vehicle into normal service.
9Tighten the wheel nuts to the specified
torque.
4 Disc brake caliper- removal,
overhaul and refitting
3
Warning: Dust created by the
brake system may contain
asbestos, which is harmful to
your health. Never blow it out
with compressed air and don’t inhale any
of it. An approved filtering mask should be
worn when working on the brakes. Do not,
under any circumstances, use petroleum-
based solvents to clean brake parts. Use
brake system cleaner only!
Note 1:The following procedure applies to
both front and rear calipers.
Note 2:If an overhaul is indicated, explore all
options before beginning the job. New andfactory rebuilt calipers are available on an
exchange basis, which makes this job quite
easy. If you decide to rebuild the calipers,
make sure a rebuild kit is available before
proceeding. Always rebuild the calipers in
pairs - never rebuild just one of them.
Removal
1Loosen the wheel nuts, raise the front or
rear of the vehicle and place it securely on
axle stands. Remove the wheel.
2If you’re just removing the caliper for
access to other components, it isn’t
Braking system 9•3
9
3.5f Remove the outer brake pad3.5g Remove the inner brake pad
3.5h Pull out the wear sensor, trace the
sensor lead back to its plug, detach the
lead from the suspension, and discard it
3.5i Remove the caliper guide pins and
boots (lower pin and boot shown) . . .
3.5j . . . clean them off, inspect the pin and
boot for damage, renew as necessary,
then lubricate the pins with brake grease
and refit them in the caliper bracket
3.5k Apply anti-squeal compound to the
new brake pads
3261 Jaguar XJ6
3.5l Insert the new wear sensor into the
inner pad as shown . . .
3.5n Refit the outer pad
3.5m . . . then refit the inner pad onto the
caliper bracket
3.5o Refit the caliper, then tighten the
mounting bolts to the specified torque

necessary to detach the brake line. If you’re
removing the caliper for overhaul, detach the
hose from the metal line at the frame bracket
(see Section 8), then disconnect the brake line
from the caliper with a flare-nut spanner to
protect the fitting (see illustration). Plug the
metal line to keep contaminants out of the
brake system and to prevent losing brake
fluid.
3Refer to illustration 3.5c and unbolt the
front or rear caliper.
Overhaul
4Before you remove the piston, place a
wood block between the piston and caliper to
prevent damage as it is removed.
5To remove the piston from the caliper,
apply compressed air to the brake fluid hose
connection on the caliper body (see
illustration). Use only enough pressure to
ease the piston out of its bore. Remove the
dust boot.
Warning: Be careful not to place
your fingers between the piston
and the caliper as the piston
may come out with some force.
Be sure to wear eye protection when using
compressed air.
6Inspect the mating surfaces of the piston
and caliper bore wall. If there is any scoring,
rust, pitting or bright areas, renew the
complete caliper unit with a new one.
7If these components are in good condition,
remove the piston seal from the caliper bore
using a wooden or plastic tool (see
illustration). Metal tools may damage the
cylinder bore.
8Remove the caliper guide pins and the
rubber dust boots from the caliper bracket.
9Wash all the components in brake system
cleaner.
10Using the correct rebuild kit for your
vehicle, reassemble the caliper as follows.11Submerge the new rubber seal in clean
brake fluid and refit it in the lower groove in
the caliper bore, making sure it isn’t twisted.
12Coat the piston with clean brake fluid and
stretch the new dust boot over the bottom of
the piston. Hold the piston over the caliper
bore and insert the rubber flange of the dust
boot into the upper groove in the bore. Start
with the side farthest from you and work your
way around toward the front until it is
completely seated. Push the piston into the
caliper bore until it is bottomed in the bore,
then seat the top of the dust boot in the
groove in the piston.
13Lubricate the sliding surfaces of the guide
pins with silicone-based grease (usually
supplied in the kit), then refit the new dust
boots and pins into the caliper bracket.
Refitting
14Refit the caliper by reversing the removal
procedure (see Section 3).
15If the brake hose was disconnected from
the caliper, bleed the brake system (see
Section 9).
5 Brake disc- inspection,
removal and refitting
2
Note:The following procedure applies to both
the front and rear brake discs.
Inspection
1Loosen the wheel nuts, raise the vehicle
and support it securely on axle stands.
Remove the wheel and refit three nuts to hold
the disc in place. If the rear brake disc is being
worked on, release the handbrake.
2Remove the brake caliper as outlined in
Section 4. It is not necessary to disconnect
the brake hose. After removing the caliper,
suspend it out of the way with a piece of wire.
3Visually inspect the disc surface for scoring
or damage. Light scratches and shallow
grooves are normal after use and may not
always be detrimental to brake operation, but
deep scoring - over 0.015 inch - requires disc
removal and refinishing by an automotive
machine shop. Be sure to check both sides of
the disc (see illustration). If pulsating has
9•4 Braking system
4.7 Remove the piston seal from the
caliper bore using a wooden or plastic tool
(metal tools may damage the
cylinder bore)5.3 The brake pads on this vehicle were
obviously neglected, as they wore down to
the rivets and cut deep grooves into the
disc - this disc must be replaced
3261 Jaguar XJ6 4.2 Use a flare-nut spanner to protect the brake hose fitting when
unscrewing it from the caliper
4.5 With the caliper padded to catch the piston, use compressed
air to force the piston out of its bore - make sure your fingers are
not between the piston and the caliper

been noticed during application of the brakes,
suspect disc runout.
4To check disc runout, place a dial indicator
at a point about 1/2-inch from the outer edge
of the disc (see illustration). Set the indicator
to zero and turn the disc. The indicator
reading should not exceed the specified
allowable runout limit. If it does, the disc
should be refinished by an automotive
machine workshop. Note:It is recommended
that the discs be resurfaced regardless of the
dial indicator reading, as this will impart a
smooth finish and ensure a perfectly flat
surface, eliminating any brake pedal pulsation
or other undesirable symptoms related to
questionable discs. At the very least, if you
elect not to have the discs resurfaced, removethe glazing from the surface with emery cloth
or sandpaper using a swirling motion (see
illustration).
5It is absolutely critical that the disc not be
machined to a thickness under the specified
minimum allowable thickness. The disc
thickness can be checked with a micrometer
(see illustration). Then compare your
measurement to the minimum wear (or discard)
thickness stamped into the hub of the disc
after the disc is removed (see illustration).
Removal
6Cut the safety wire from the caliper bracket
mounting bolts (see illustration). On front
caliper brackets, remove the ABS wheelspeed sensor (see illustration), then remove
the caliper bracket bolts and remove the
bracket.
7Remove the disc retaining screw (see
illustration) and remove the disc from the
hub. If the disc sticks, give it a few sharp raps
with a hammer (see illustration). If the disc is
stuck to the hub, spray a generous amount of
penetrant onto the area between the hub and
the disc and allow the penetrant a few
minutes to loosen the rust between the two
components. If a rear disc still sticks, insert a
thin, flat-bladed screwdriver or brake
adjusting tool through the hub flange, rotate
the star wheel on the handbrake adjusting
screw and contract the handbrake shoes (see
illustration).
Braking system 9•5
9
5.4a To check disc runout, mount a dial
indicator as shown and rotate the disc5.4b Using a swirling motion, remove the
glaze from the disc surface with
sandpaper or emery cloth5.5a The disc thickness can be checked
with a micrometer
5.5b Compare your measurement with the
minimum thickness stamped into the disc5.6a Before you can remove the caliper
mounting bracket bolts (arrowed) and the
bracket, you’ll have to cut the safety wire
between them with a pair of diagonal
cutters (rear bracket shown)5.6b On front caliper brackets, remove the
ABS wheel speed sensor bolt (centre
arrow) and pull out the sensor before
removing the bracket bolts (upper and
lower arrows) and bracket
3261 Jaguar XJ6
5.7a Using an impact driver, if necessary,
remove the disc retaining screw, then
remove the disc from the hub5.7c If a rear disc is stuck to the hub,
insert a suitable tool through the hub
flange and retract the handbrake shoes5.7b If the disc is stuck to the hub, give it
a few sharp raps with a hammer

Refitting
8Place the disc on the hub and refit the disc
retaining screw. Tighten the screw securely.
9Refit the caliper mounting bracket, using a
new safety wire on the mounting bolts.
10Refit the brake pads and caliper (see
Section 3). Tighten all fasteners to the torque
listed in this Chapter’s Specifications.
11Refit the wheel and wheel nuts, then lower
the vehicle to the ground. Tighten the wheel
nuts to the specified torque (see Chapter 1
Specifications). Depress the brake pedal a
few times to bring the brake pads into contact
with the disc.
12Adjust the handbrake shoes, if necessary.
13Check the operation of the brakes
carefully, if possible before driving the vehicle
on public roads.
6 Master cylinder- removal,
overhaul and refitting
3
Note:Although master cylinder parts and
rebuild kits are available for most models, we
recommend replacing the master cylinder with
a new or remanufactured unit, if possible.
Removal
1The master cylinder is connected to the
brake servo, which is attached to the pedal
box, in front of the bulkhead on the driver’s
side of the engine compartment.
2Remove as much fluid as you can from the
reservoir with a syringe.
3Place rags under the line fittings and
prepare caps or plastic bags to cover the
ends of the lines once they are disconnected.
Caution: Brake fluid will damage paint.
Cover all body parts and be careful not to
spill fluid during this procedure.
4Disconnect the electrical connector for the
low fluid level warning light (see illustration).
5Loosen the brake line fittings at the mastercylinder (see illustration). Use a flare-nut
spanner to prevent rounding off the nuts. Pull
the brake lines away from the master cylinder
slightly and plug the ends to prevent
contamination.
6Remove the nuts attaching the master
cylinder to the servo (see illustration). Pull
the master cylinder off the studs and lift it out
of the engine compartment. Again, be careful
not to spill fluid as this is done.
Overhaul
7Follow the accompanying photo sequence,
beginning with illustration 6.7a. Stay in order,don’t skip steps, read each caption and study
the photo carefully.
8Once you have dismantled the master
cylinder, clean everything thoroughly, blow
the parts dry with compressed air and
carefully inspect the secondary piston and the
bore of the master cylinder with a bright light.
If the secondary piston or the master cylinder
bore is damaged or worn, renew the master
cylinder with a new or rebuilt unit.
Bench bleeding procedure
9Before refitting a new or rebuilt master
cylinder it should be bench bled. Because it
9•6 Braking system
6.7a Knock out the roll pin that secures
the reservoir to the master cylinder
6.7b Carefully pry off the reservoir by
inserting a screwdriver between the
reservoir and each grommet; this takes
firm pressure, so don’t slip and damage
the reservoir or the master cylinder
6.7c Remove the grommets, noting the
position of each one
6.6 Remove the two master cylinder
mounting nuts
3261 Jaguar XJ6 6.4 Trace the electrical lead back from the reservoir cap and
disconnect the low fluid level sensor
6.5 Loosen the hydraulic brake line fittings with a flare-nut
spanner to protect the corners of the nuts

being drawn back into the master cylinder.
Wait several seconds for brake fluid to be
drawn from the reservoir into the piston bore,
then depress the piston again, removing your
finger as brake fluid is expelled. Be sure to put
your finger back over the hole each time
before releasing the piston, and when the
bleeding procedure is complete for that outlet,
renew the plug and snug it up before going on
to the other port.
Refitting
16Refit the master cylinder over the studs on
the brake servo and tighten the mounting nuts
only finger tight at this time.
17Thread the brake line fittings into the
master cylinder. Since the master cylinder is
still a bit loose, it can be moved slightly to
allow the fitting threads to start easily. Do not
strip the threads as the fittings are tightened.
18Tighten the brake fittings securely and the
mounting nuts to the torque listed in this
Chapter’s Specifications.
19Fill the master cylinder reservoir with fluid,
then bleed the master cylinder and the brake
system (see Section 9).
20To bleed the master cylinder on the
vehicle, have an assistant pump the brake
pedal several times and then hold the pedal to
the floor. Loosen the fitting nut to allow air and
fluid to escape, then tighten the nut. Repeat
this procedure on both fittings until the fluid is
clear of air bubbles. Test the operation of the
brake system carefully before placing the
vehicle into service.
7 Brake servo-
general information,
removal and refitting
2
General information
1A hydraulic brake servo system assists
braking when the brake pedal is depressed.
The booster unit, located between the brake
pedal box and the master cylinder, is operated
by hydraulic pressure generated by an engine-
driven pump (on early models) or by an electric
pump (on later models). When the engine isrunning, the pump supplies hydraulic pressure
to an accumulator. The accumulator stores and
regulates the pressure to the hydraulic brake
servo. When you depress the brake pedal, the
pressure in the booster helps actuate the
master cylinder, reducing pedal effort.
2The hydraulic brake servo isn’t rebuildable;
if it fails, it must be replaced. Basic operation
can be checked (see Chapter 1, Section 15),
but in-depth testing of the system requires
special tools, so diagnosis is beyond the
scope of the home mechanic. If the system
fails, take it to a dealer service department or
other qualified repair workshop for repairs.
However, if the unit must be replaced, you
can do it yourself as follows.
Removal and refitting
3With the engine off, discharge the hydraulic
accumulator by depressing the brake pedal
several times until it feels hard to depress.
4Remove the master cylinder (see Section 6).
5Clean the area around the return and
supply tube nuts, then disconnect them with a
flare-nut spanner (see illustration). Plug the
lines to prevent dirt from entering the system.
Caution: Even a particle of dirt can damage
the servo system, so be extremely careful
to prevent dirt from entering the system
while the lines are disconnected.
6To disconnect the brake servo pushrod
from the brake pedal, remove the access
plugs from both sides of the pedal box (see
illustration), remove the clevis pin retaining
clip and drive out the clevis pin.
7Remove the four mounting nuts and
remove the brake servo (see illustration).
8Refitting is the reverse of removal. Tighten
the hydraulic line fittings securely.
9When you’re done, adjust the brake light
switch (see Section 13).
8 Brake hoses and lines-
inspection and renewal
4
Inspection
1About every six months, with the vehicleraised and placed securely on axle stands, the
flexible hoses which connect the steel brake
lines with the front and rear brake assemblies
should be inspected for cracks, chafing of the
outer cover, leaks, blisters and other damage.
These are important and vulnerable parts of
the brake system and inspection should be
complete. A light and mirror will prove helpful
for a thorough check. If a hose exhibits any of
the above conditions, renew it with a new one.
Flexible hose renewal
2Clean all dirt away from the ends of the
hose.
3To disconnect the hose at the frame end,
use a second spanner on the hex-shaped
fitting on the end of the flexible hose and
loosen the nut on the metal brake line (see
illustrations). If the nut is stuck, soak it with
penetrating oil. After the hose is disconnected
from the metal line, remove the nut right
above the bracket and detach the hose from
the bracket.
4To detach the flexible hose from the caliper,
simply unscrew it.
5Refitting is the reverse of the removal
procedure. Make sure the brackets are in
good condition and the locknuts are tightened
securely.
Braking system 9•9
9
7.5 Use a flare-nut spanner to loosen the
fittings, then pull the lines back from the
brake servo and plug them to prevent
contamination7.6 Pry off the two rubber caps from the
pedal box7.7 To detach the brake servo from the
pedal box, remove these four nuts
(arrowed) (lower right nut not visible
in this photo)
8.3a To remove a front flexible brake hose
from a metal brake line, use one spanner
to hold the hose fitting just below the
bracket (lower spanner), then break loose
the nut on the metal line (upper spanner);
to disconnect the flex hose from the
bracket, remove the centre nut (arrowed)
just above the bracket
3261 Jaguar XJ6