Jaguar XK. Service manual - part 41

167

Brakes

PRINCIPLE OF OPERATION

Brake pads

Brake pads require a period of bedding in
when new. Drive with extra caution for the
first 800 km (500 miles) to avoid the need
for heavy braking.

Wet conditions

Driving through heavy rain or water can
have an adverse effect on braking
efficiency. Under those circumstances, it
is recommended that you lightly apply the
brakes intermittently to dry the brakes.

Anti-lock Braking System (ABS)

This system helps to prevent the road
wheels from locking and skidding during
emergency braking, assisting the driver
to maintain full steering and directional
stability.

The factor controlling ultimate stopping
distance and cornering ability is tyre to
road adhesion.

ABS optimises tyre to road adhesion
under maximum braking conditions
though it cannot provide increased
cornering ability.

During normal braking the ABS will not be
activated. However, if the braking force
applied begins to exceed tyre to road
adhesion the ABS will automatically
activate, preventing the road wheels from
locking.

In these circumstances a pulsating effect
will be felt from the brake pedal indicating
that the system is functioning. The
pulsating effect is due to small
fluctuations in pressure supplied to the
brakes by the system to maintain full tyre
to road adhesion.

Under severe braking on some road
surfaces tyre noise may be apparent even
though the wheels will at no time become
locked.

ABS monitoring

If this warning indicator
illuminates, drive with extra
caution, avoid heavy braking

where possible, and seek qualified
assistance as soon as possible.

WARNINGS

It remains the driver’s
responsibility to drive safely
according to prevailing

conditions.

Do not rest your foot on the brake
pedal whilst the vehicle is in
motion. This may cause a light

application of the brakes, which can
result in overheating, reduced brake
performance, and excessive brake wear.

If the red brake warning indicator
illuminates, safely bring the
vehicle to a stop, as quickly as

possible. Seek qualified assistance
before proceeding.

Never place non-approved floor
matting or any other obstructions
under the brake pedal. This

restricts pedal travel and braking
efficiency.

Brakes

168

The ABS control module monitors the
ABS electrical system from ignition
system ON to ignition system OFF. Any
malfunction will be indicated by the
anti-lock warning indicator illuminating
and a message ABS FAULT will be
displayed by the message centre.

Should a fault develop in the ABS system,
the brake system will still operate
conventionally and with the same
standard of performance as vehicles not
equipped with ABS.

Emergency Brake Assist (EBA)

The EBA system measures the rate at
which the brake pressure increases. If the
system detects an emergency braking
situation, EBA automatically initiates the
full braking effect. This can reduce
stopping distances in critical situations,
which can help an inexperienced driver to
stop in the same distance as an
experienced driver.

Any malfunction will be indicated by the
message BRAKE ASSIST FAULT
displayed by the message centre.
Increased brake pedal effort may be
required to slow the vehicle. Seek
qualified assistance as soon as possible.

HINTS ON DRIVING WITH ABS

For optimum ABS performance these
instructions on braking techniques during
ABS operation should be followed:
• Do not release brake pressure when

the pulsating effect is felt. Maintain a
constant pressure until the
manoeuvre is completed.

• To familiarise yourself with the feel of

the brake pedal during ABS braking,
practise an emergency stop
procedure, always making sure it is
safe to do so. With the seat belts
fitted to all occupants, drive the
vehicle at 32 km/h (20 mph) and
brake sharply.

• ABS enables the driver to steer

around obstacles during emergency
braking. However, the consequences
of turning sharply at high speed
cannot be overcome by the ABS.

WARNING

The EBA system is an additional
safety system; it is not intended to
relieve the driver of his or her

responsibility for exercising due care and
attention when driving.

WARNINGS

ABS cannot overcome the
physical limitations of braking
distance. Nor can it overcome the

lack of grip on a road surface,
aquaplaning on water for example.

Braking distance is increased on a
slippery or wet surface. This
applies to all vehicles, even those

fitted with ABS.

The driver should not be tempted
to take risks when driving, in the
hope that ABS will correct errors

of judgement. In all cases, it remains the
driver's responsibility to drive with due
care and attention, paying particular
attention to the effects of speed,
weather, road conditions etc.

169

Brakes

• Do not attempt to pump the brakes to

avoid skidding as this can interfere
with the ABS operation. The ABS will
not allow the wheels to skid under
normal road conditions.

• The ABS will maintain to keep the

vehicle straight during braking.
Because braking distances may
increase under certain road
conditions, it is necessary to plan and
make turning manoeuvres as early as
possible.

ELECTRIC PARKING BRAKE
(EPB)

The switch which operates the park brake
is mounted on the centre console to the
rear of the gear selector.

To engage the park brake 1: Pull the
park brake switch upwards and release.
The switch will return to the neutral
position. The park brake warning and
brake fluid low warning indicator on the
instrument panel will illuminate.

The Drive Away Release feature allows
the park brake to release automatically as
the vehicle is driven away.

To disengage the park brake 2: With the
ignition system in the ON position or with
the engine running, apply the foot brake
and press the park brake switch down.

If the park brake is applied while the
vehicle is stationary and D or R is
selected, applying the throttle will
automatically release the park brake.

The park brake is also automatically
released when the gear selector is moved
from P position.

Inadvertent operation of the parkbrake
whilst the vehicle is in motion, above 3
km/h (1.8 mph), will cause the message
PARK BRAKE APPLIED to be displayed
on the message centre, the warning
indicator in the instrument panel will be
illuminated and a warning chime will
sound.

If the park brake is applied whilst the
vehicle is moving, releasing the switch
will disengage the park brake. The park
brake cannot be applied whilst the
vehicle is moving and the throttle
pressed.

Note: If the vehicle is in motion, the park
brake should only be used as an
emergency brake.

The warning indicator in the instrument
panel will remain on for a short time if the
park brake is applied when the ignition
system is reverted to the convenience
mode.

E91475

CAUTION

Take care that the vehicle is safely
parked to prevent it from rolling if
you wish to leave the park brake

off. However, it is advisable to always
use the park brake.

Brakes

170

If a fault in the system is detected, a
message PARK BRAKE FAULT or
CANNOT APPLY PARK BRAKE will be
displayed. Seek qualified assistance as
soon as possible.

If the battery has been discharged or
disconnected a message APPLY FOOT
AND PARK BRAKE will be displayed
when the ignition is next switched on.
Depress the footbrake and pull the park
brake switch up to apply the park brake.
This is required to reset the park brake
system. The park brake will now function
correctly.

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