Brake System - Volvo 2009 XC90 Owner's Manual

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
Brake failure – Service
reservoir or if a
urgent
message is displayed in the text
DO NOT DRIVE
window: . 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, the brake
pedal must be pressed approximately four
times harder than usual to make up for the lack
of power assistance. This can happen for
example when towing your vehicle or if the
engine is switched off when the vehicle is roll-
ing. 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.
06 Starting and driving

Brake system

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 warning lamp lights up there
is a malfunction of 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
system "senses" impending lockup, braking
pressure 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
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