1. With the engine off, press the brake pedal several times, the brake pedal travel should not change.
2. Step on the pedal and start the engine. After starting the engine, the pedal should move forward a little.
3. Press the brake pedal and stop the engine. For about 30 seconds, the pedal should hold its position.
4. Start the engine again, after 1 minute stop and press the pedal several times. The pedal travel should decrease with each press.
5. If the operation of the vacuum booster differs from that described above, then the unit must be replaced (see subsection 8.11).