Volvo XC90 owner manual Brake system, Brake Brake circuit malfunction

06 Starting and driving

Brake system

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-

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