1998 Toyota 4Runner Owners Manual - Page 227

4RUNNER (1998) Your engine is fitted with twin ground electrode spark plugs. Brake system TANDEM MASTER BRAKE SYSTEM CYLINDER NOTICE Use only twin ground electrode spark plugs for your engine performance. The tandem master cylinder brake system is a hydraulic system with two separate sub- systems. If either subsystem should fail, the other will still work. However, the pedal will be harder to press, and your stopping distance will be longer. Also, the brake system warning light may come on. The brake booster uses engine vacuum to power- assist the brakes. If the engine should quit while you are driving, you can bring the vehicle to a stop with normal pedal pressure. There is enough reserve vacuum for one or two stops-but no more! CAUTION D Do not pump the brake pedal if the engine stalls. Each push on the pedal uses up your vacuum reserve. CAUTION Do not drive your vehicle with only a single brake system. Have your brakes fixed immediately. BRAKE BOOSTER