2. With the engine not running, press the brake pedal several times until the hissing sound in the brake booster stops.
3. Press the brake pedal and hold it down.
4. Without releasing the brake pedal, start the car engine.
5. If immediately after starting the engine the brake pedal goes down a little, then the brake booster is working properly.
(The information is posted on the portal: «VazBook»)
6. Otherwise, check the integrity of the vacuum supply hose to the vacuum booster, the tightness of its connection to the inlet module and the branch pipe of the vacuum booster check valve. If the hose is in good condition and is tightly connected, the vacuum booster is faulty.
Diagram of the brake system: 1 - front left wheel brake mechanism; 2, 6, 12, 17 - brake hoses; 3, 7, 11, 18 - brake pipes; 4 - master brake cylinder; 5 - front right wheel brake mechanism; 8 - master brake cylinder reservoir; 9 - brake booster; 10 - brake pedal; 13 - rear right wheel brake mechanism; 14 - brake fluid pressure regulator in the rear wheel brake mechanisms; 15 - brake fluid pressure regulator lever in the rear wheel brake mechanisms; 16 - rear left wheel brake mechanism