1. Let the engine run for 1 or 2 minutes and then turn it off. Depress the brake pedal several times with normal force. If the pedal goes far down on the first press, but gradually rises after the second or third press, this means the brake booster is working normally.
2. With the engine off, depress the brake pedal several times. With the pedal depressed, start the engine. If the pedal comes down slowly, the booster is working properly.
3. With the engine running, depress the brake pedal and then turn off the engine. Keep the pedal depressed for 30 seconds. If the pedal height does not change, the brake booster is working properly.
If one of the above three operations gives a negative result, check the vacuum hoses and brake booster and then make the necessary corrections. If all operations give positive results, this means that the brake booster is in good condition.