Volvo XC90 - Manual (Page 149)

06 Starting and driving
Brake system
06
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149
BRAKE Brake circuit malfunction
The brake system is a hydraulic system con-
sisting of two master cylinders and two sepa-
rate brake circuits. If a problem should occur in
one of these circuits, it is still possible to stop
the vehicle with the other brake circuit.
If the brake pedal must be depressed farther
than normal and requires greater foot pressure,
the stopping distance will be longer.
A warning light in the instrument panel will light
up to warn the driver that a fault has occurred.
If this light comes on while driving or braking,
stop immediately and check the brake fluid
level in the reservoir.
NOTE
Press the brake pedal hard and maintain
pressure on the pedal – do not pump the
brakes.
WARNING
If the fluid level is below the MIN mark in the
reservoir or if a
Brake failure – Service
urgent message is displayed in the text
window: DO NOT DRIVE . Have the vehicle
towed to a trained and qualified Volvo serv-
ice technician and have the brake system
inspected.
NOTE
When the vehicle is at a standstill and the
engine is idling, e.g. at a traffic light and the
brake pedal is depressed, the pedal may go
down slightly. This is a normal function of
the power-assisted brake system.
Power brakes function only when the
engine is running
The power brakes utilize vacuum pressure
which is only created when the engine is run-
ning. Never let the vehicle roll to a stop with the
engine switched off.
If the power brakes are not working, consider-
ably higher pressure will be required on the
brake pedal to compensate for the lack of
power assistance. This can happen for exam-
ple when towing your vehicle or if the engine is
switched off when the vehicle is rolling. The
brake pedal feels harder than usual.
Water on brake discs and brake pads
affects braking
Driving in rain and slush or passing through an
automatic car wash can cause water to collect
on the brake discs and pads. This will cause a
delay in braking effect when the pedal is
depressed. To avoid such a delay when the
brakes are needed, depress the pedal occa-
sionally when driving through rain, slush etc.
This will remove the water from the brakes.
Check that brake application feels normal. This
should also be done after washing or starting
in very damp or cold weather.
Severe strain on the brake system
The brakes will be subject to severe strain
when driving in mountains or hilly areas, or
when towing a trailer. Vehicle speed is usually
slower, which means that the cooling of the
brakes is less efficient than when driving on
level roads. To reduce the strain on the brakes,
shift into a lower gear and let the engine help
with the braking. Do not forget that, if you are
towing a trailer, the brakes will be subjected to
a greater than normal load.
Anti-lock brakes (ABS)
If the ABS warning lamp lights up there is a
malfunction in the ABS system (the standard
braking system will however function) and the
vehicle should be driven cautiously to a trained
and qualified Volvo service technician for
inspection. The Anti-lock Braking System
(ABS) helps to improve vehicle control (stop-
ping and steering) during severe braking con-
ditions by limiting brake lockup. When the sys-
tem "senses" impending lockup, braking pres-
sure is automatically modulated in order to help
prevent lockup, which could lead to a skid.
The system performs a self-diagnostic test
when the engine is started and when the
vehicle first reaches a speed of approxi-