1. Start the engine and after 1-2 minutes, stop it. Press the brake pedal with ordinary effort. If the first pedal stroke is long and the second course is shorter than the first move - this indicates normal operation of the vacuum brake booster.
2. With the engine off, repeatedly press the brake pedal. Start the engine. If the brake pedal is moved down immediately after the engine starts, it indicates normal operation of the vacuum brake booster.
3. Start the engine. Press the brake pedal with ordinary effort. Stop the engine. Slowly depress the brake pedal and hold it for 30 seconds. If the pedal height does not change, the vacuum brake booster is working properly. Otherwise, check up the unilateral vacuum valve or a vacuum hose for damage and check the reliability of their fastenings.