Vacuum Brake Booster: Testing and Inspection

34 00 017 - Checking brake booster (low-pressure test)





Special tools required:
- 34 3 100 34 3 100 Brake Booster Tester





- Release clamp and detach vacuum hose. Connect vacuum tester 34 3 100 34 3 100 Brake Booster Tester between connection and vacuum hose at non-return valve.
- Start engine.
- Check whether a vacuum forms.
- Switch off engine.
- Depress brake pedal to set a maximum value of 0.8 bar and wait until the value stabilizes.
- When the brake pedal is not depressed, the vacuum may drop by a maximum of 0.06 bar within a test period of 1 minute.

If the specified values are not reached:
- Check line connections for leaks.
- Replace non-return valve.
- Check that seals between brake booster and brake master cylinder (sealing ring) are in perfect condition and that seal seating is correct.
- Replace the brake booster if the specified values are still not reached after repeating the test procedure.