2006 Lexus GS 300 Owners Manual - Page 451

STARTING AND DRIVING BRAKE SYSTEM This brake system has 2 independent hydraulic circuits. If either circuit should fail, the other will still work. However, the pedal will be harder to press, and your stopping distance will increase. Also, the brake system warning light may come on. GS430: You may hear a small sound in the engine compartment after the engine is started or the brake pedal is depressed repeatedly. This is a pump pulsating sound of the brake system, and it is not a malfunction. GS300: If the engine should stop while you are driving, you can bring the vehicle to a stop with normal pedal pressure. There is enough reserved vacuum for one or two stops-but no more! CAUTION Do not drive your vehicle with only a single brake system. Have your brakes fixed immediately. Brake booster The brake booster uses brake fluid pressurized by the pump (GS430) or engine vacuum (GS300) to power−assist the brakes. If the brake booster fails during driving, the brake system warning light (red) comes on. In this case, the brakes may not work properly. If they do not work well, depress the brake pedal firmly. If the brake system warning light (red) comes on, immediately stop your vehicle and contact your Lexus dealer. GS430 only-Either of the following conditions may occur, but does not indicate a malfunction: D The brake system warning light (red) may stay on for about 60 seconds after the engine is started. It is normal if the light turns off after a while. D Depressing the brake pedal repeatedly may turn on the brake system warning light (red). It is normal if the light goes out after a few seconds. CAUTION D Do not pump the brake pedal if the engine stalls. Each push on the pedal uses up your brake fluid pressure reserve. D Even if the power assist is completely lost, the brakes will still work. But you will have to push the pedal hard, much harder than normal. And your braking distance will increase. 427