2007 Volvo S40 Owner's Manual - Page 127

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 system message is shown in the information display: DO NOT DRIVE. Have the vehicle towed to a Volvo retailer and have the brake system inspected. Power brakes function only when the engine is running The power brakes utilize vacuum pressure which is only created when the engine is running. 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 five 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 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 occasionally 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) The Anti-lock Braking System (ABS) helps to improve vehicle control (stopping and steering) during severe braking conditions by limiting brake lockup. When the system "senses" impending lockup, braking pressure is automatically modulated in order to help prevent lockup that 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 approximately 12 m.p.h. (20 km/h). The brake pedal will pulsate several times and a sound may be audible from the ABS control module. This is normal. 141 06 Starting and driving Brake system For optimal ABS braking effect: 1. Press down on the brake pedal with full force. The pedal will pulsate.