Checking the brake booster (vacuum test) (4' Series Coupe/Convertible, 4' Series Gran Coupe Sedan)
Special tools required:
- 34 3 100
Preliminary work needed:
- If necessary, uncover brake booster
- Detach the vacuum hose from the brake booster. Install the vacuum tester 34 3 100 between the brake booster and the vacuum hose of the check valve.
- Start the engine.
- Check the build-up of the vacuum.
- Switch off engine.
- Set a vacuum of no more than 0.8 bar by pressing the brake pedal and wait for the value to stabilize.
- When the brake pedal is not depressed, the vacuum may drop by a maximum of 0.06 bar during a test period of 1 minute.
If the required values are not achieved:
- Replace the check valve
- Check the seal between the brake booster and the tandem brake master brake cylinder (sealing ring) for proper condition and correct sealing fit.
- If necessary, check the brake booster for leaks with a smoke tester
- If the setpoint values are not reached after another check, the brake booster must be replaced.