Ref 1 JAGUAR XJ6 1997 2.G Workshop Manual

obstructions to ensure complete recirculation
of gasses from the crankcase back into the
intake manifold. In the event of clogging, the
pressure will increase causing blow-by and oil
leaks through seals and gaskets.
6Check the operation of the heating element.
Check for battery voltage to the element while
the engine is cold. If no voltage is available
to the heating element, check the circuit from
the windscreen washer jet temperature
sensor.
Renewal
7Disconnect the electrical connector from
the heating element (see illustration).
8Remove the clamps from the hoses and
separate the heating element from the engine.
9Remove the hoses from the intake
manifold. These crankcase ventilation hoses
are specially formed and must be replaced
with special factory parts from Jaguar.
10Refitting is the reverse of removal.
9 Catalytic converter
General description
1To reduce hydrocarbon, carbon monoxide
and oxides of nitrogen emissions, all vehicles
are equipped with a three-way catalyst
system which oxidises and reduces these
chemicals, converting them into harmless
nitrogen, carbon dioxide and water.
2The catalytic converter fits into the exhaust
system much like a silencer. Note:The
exhaust system configuration changes withlater model updates. Older models (1988 and
1989) are equipped with a pre-catalytic
converter near the exhaust manifold
incorporating a single exhaust pipe to the
silencer. Later models are equipped with dual
exhaust pipes, dual catalytic converters and
dual silencers.
Check
3Periodically inspect the catalytic converter-
to-exhaust pipe mating flanges and bolts.
Make sure that there are no loose bolts and
no leaks between the flanges.
4Look for dents in or damage to the catalytic
converter protector. If any part of the
protector is damaged or dented enough to
touch the converter, repair or renew it.
5Inspect the heat insulator for damage.
Make sure there is enough clearance between
the heat insulator and the catalytic converter.
Renewal
6To renew the catalytic converter, refer to
Chapter 4. It is recommended that catalytic
converters be renewed at a qualified silencer
workshop because of the numerous tack
welds on the exhaust pipes.
6•12 Emissions and engine control systems
3261 Jaguar XJ6
8.7 Disconnect the electrical connector
from the electronic heating element

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.

Test the brakes at various speeds with both
light and heavy pedal pressure. The vehicle
should stop evenly without pulling to one side
or the other. Avoid locking the brakes,
because this slides the tyres and diminishes
braking efficiency and control of the vehicle.
Tyres, vehicle load and wheel alignment are
factors which also affect braking performance.
2 Anti-lock Brake system
(ABS)- general information
The Anti-lock Brake System is designed to
maintain vehicle steerability, directional stability
and optimum deceleration under severe
braking conditions on most road surfaces. It
does so by monitoring the rotational speed of
each wheel and controlling the brake line
pressure to each wheel during braking. This
prevents the wheels from locking up.
The ABS system has three main units - the
wheel speed sensors, the electronic control unit
and the modulator (hydraulic control unit). The
sensors - one at each wheel - send a variable
voltage signal to the electronic control unit,
which monitors these signals, compares them
to its program and determines whether a wheel
is about to lock up. When a wheel is about to
lock up, the control unit signals the hydraulic
unit to reduce hydraulic pressure (or not
increase it further) at that wheel’s brake caliper.
Pressure modulation is handled by three
electrically-operated solenoid valves - one for
each front wheel and one for the rear wheels -
inside the modulator.
If a problem develops within the system, an
“ABS” warning light will glow on the dashboard.
Sometimes, a visual inspection of the ABS
system can help you locate the problem.
Carefully inspect the ABS wiring harness. Pay
particularly close attention to the harness and
connections near each wheel. Look for signs of
chafing and other damage caused by
incorrectly routed wires. If a wheel sensor
harness is damaged, the sensor should be
replaced (the harness and sensor are integral).
Warning: Do NOT try to repair an
ABS wiring harness. The ABS
system is sensitive to even thesmallest changes in resistance. Repairing
the harness could alter resistance values
and cause the system to malfunction. If the
ABS wiring harness is damaged in any way,
it must be replaced.
Caution: Make sure the ignition is turned
off before unplugging or reattaching any
electrical connections.
Diagnosis and repair
If a dashboard warning light comes on and
stays on while the vehicle is in operation, the
ABS system requires attention. Although
special electronic ABS diagnostic testing tools
are necessary to properly diagnose the system,
you can perform a few preliminary checks
before taking the vehicle to a dealer service
department or other qualified repair workshop.
a) Check the brake fluid level in the master
cylinder reservoir.
b) Verify that all ABS system electrical
connectors in the engine compartment
are plugged in.
c) Check the fuses.
d) Follow the wiring harness to each front
wheel and to the differential sensor and
verify that all connections are secure and
that the wiring is undamaged.
If the above preliminary checks do not
rectify the problem, the vehicle should be
diagnosed by a dealer service department.
Due to the complex nature of this system, all
actual repair work must be done by a dealer
service department or other qualified repair
workshop.
3 Disc brake pads- renewal
2
Warning: Disc brake pads must
be replaced on both front wheels
or both rear wheels at the same
time - never renew the pads on
only one wheel. Also, the 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:The following procedure applies to both
the front and rear brake pads.
1Remove the cap from the brake fluid
reservoir and siphon off about two-thirds of
the fluid from the reservoir. Failing to do this
could result in fluid overflowing when the
caliper pistons are pressed into their bores.
2Loosen the wheel nuts, raise the front of the
vehicle and support it securely on axle stands.
3Remove the front wheels. Work on one
brake assembly at a time, using the
assembled brake for reference if necessary.
4Inspect the brake disc (see Section 5).
5Follow the accompanying photos,
beginning with illustration 3.5a, for the pad
removal procedure. Be sure to stay in order
and read the caption under each illustration.
9•2 Braking system
3.5a Before starting, wash down the
caliper and disc with brake cleaner
3.5b Attach a hose to the bleed screw,
open the bleed screw slightly and depress
the piston into the caliper. Tighten the
bleed screw when the piston bottoms
3.5c Remove the caliper mounting bolts
(upper bolt arrowed); use another spanner
to hold the flats of the caliper guide pins
while you back out the caliper bolts3.5d Remove the caliper . . .3.5e . . . and suspend it out of the way
with a piece of wire
3261 Jaguar XJ6

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

Braking system 9•7
9
6.7d Pry off the end cap6.7e Locate the stopper pin (arrowed)
inside the forward grommet hole . . .6.7f . . . insert a punch into the pocket of
the primary piston, place the master
cylinder vertically as shown, push down
on the master cylinder to depress the
pistons and pull out the stopper pin
with a magnet
6.7g Remove the primary piston6.7h Remove the secondary piston6.7i If the secondary piston is stuck, rap
the master cylinder on a wood block to
dislodge it
3261 Jaguar XJ6
6.7j Remove the seals and cups from the
pistons - be very careful not to scratch the
piston surface - then wash the secondary
piston with clean brake fluid and inspect it;
if the secondary piston is damaged, you
must renew the master cylinder with a new
or rebuilt unit (a new primary piston is
included with the rebuild kit)6.7l The master cylinder assembly
1 Roll pin
2 Reservoir
3 Grommets
4 End plate
5 Primary piston
6 Secondary piston stopper pin
7 Secondary piston6.7k Refit the new O-ring seals and cups
as shown; make sure the cups on the
primary piston (the one on the left) face
forward as shown (toward the spring), and
the cups on the secondary piston (the one
on the right) face out, away from the piston
(the one on the left faces toward the
primary piston, the one on the right faces
toward the spring)

will be necessary to apply pressure to the
master cylinder piston and, at the same time,
control flow from the brake line outlets, it is
recommended that the master cylinder be
mounted in a vice. Use caution not to clamp
the vice too tightly, or the master cylinder
body might crack.
10Insert threaded plugs into the brake line
outlet holes and snug them down so that
there will be no air leakage past them, but not
so tight that they cannot be easily loosened.
11Fill the reservoir with brake fluid of the
recommended type (see Recommended
lubricants and fluidsin Chapter 1).
12Remove one plug and push the piston
assembly into the master cylinder bore to
expel the air from the master cylinder. A large
Phillips screwdriver can be used to push on
the piston assembly.
13To prevent air from being drawn back into
the master cylinder, the plug must be
replaced and tightened before releasing the
pressure on the piston assembly.
14Repeat the procedure until only brake
fluid is expelled from the brake line outlet
hole. When only brake fluid is expelled, repeat
the procedure with the other outlet hole and
plug. Be sure to keep the master cylinder
reservoir filled with brake fluid to prevent the
introduction of air into the system.
15Since high pressure is not involved in the
bench bleeding procedure, an alternative to
the removal and renewal of the plugs witheach stroke of the piston assembly is
available. Before pushing in on the piston
assembly, remove the plug as described inStep 12. Before releasing the piston, however,
instead of replacing the plug, simply put your
finger tightly over the hole to keep air from
9•8 Braking system
6.7m Apply some clean brake fluid to the
secondary piston and refit it with the slot
oriented with the stopper pin hole, so that
the stopper pin will go through the slot6.7n Apply a coat of clean brake fluid to
the primary piston and refit it into the bore6.7o Using the same technique as in
illustration 6.7f, depress the pistons and
refit the stopper pin
6.7p Refit the end plate as shown, with the
bend in the plate flange aligned with the
groove in the master cylinder flange6.7q Using a hammer and punch, stake
the end plate as shown (there’s a dimple in
the side of the plate for this purpose)6.7r Refit the grommets
3261 Jaguar XJ6
6.7s Align the reservoir pipes with the
grommets as shown . . .
6.7u Refit the reservoir roll pin . . .6.7v . . . and tap it into place
6.7t . . . and squeeze the reservoir and
master cylinder together; make sure the
reservoir is fully seated

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