1.3.3.5.3. Vacuum hoses
In spite of the fact that the brake system hydraulic, the amplifier of brakes increases the effort made for a brake pedal, using the vacuum in an inlet collector created during the operation of the engine. Vacuum is transmitted to the amplifier through a hose of big section. Any leakage of this hose will reduce efficiency of the brake system.
Leak in a vacuum hose means that air is sucked in in a hose, but does not come out a hose, and it does leak very difficult for detection. The method of detection consists in using an old vacuum hose as some kind of stethoscope. At the same time you hold one end of a hose close to an ear, and use other end to explore the area around alleged leak. When the end of a hose directly is over the place of leak, the hissing sound will be clearly heard through an additional hose. It is necessary to avoid contact with hot and moving details as the engine when checking has to work. Replace all found untight vacuum hoses.