34 00 017 Checking the brake booster (vacuum test)

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.

  Courtesy of BMW OF NORTH AMERICA, INC.

• 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.