Vacuum brake booster — check

1. We prepare the car for work (see "Preparing the car for maintenance and repair").

2. With the engine off, press the brake pedal several times until the hissing in the brake booster stops.

3. Press the brake pedal and hold it down.

4. Without releasing the pedal, start the engine.

5. If immediately after starting the engine the pedal went down a little, then the brake booster is working.

Otherwise, check the integrity of the vacuum supply hose to the vacuum booster, the tightness of its connection to the inlet receiver and the booster check valve pipe. If the hose is serviceable and connected hermetically, the vacuum booster is faulty.