a) Press the brake pedal several times with the engine off and check that the pedal travel does not change.
b) Press the brake pedal and start the engine. If the brake pedal goes down smoothly, the vacuum booster is working.
2. Checking air tightness.
a) Start the engine and stop it after one or two minutes of operation. Slowly press the brake pedal several times. If the pedal drops lower on the first press than on the second and third press, the vacuum booster is sealed.
b) Press the brake pedal with the engine running and stop it with the pedal pressed. If the distance between the floor and the pressed pedal does not change within thirty seconds, the vacuum booster is sealed.
The publication is taken from the website [toyotaman.ru]