Vacuum Brake Booster: Testing and Inspection

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

Special tools required:
^ 34 3 100





^ Detach hose from connection piece. Install vacuum tester 34 3 100 between connection piece and vacuum hose of non-return valve.
^ Start engine.
^ Check buildup of partial vacuum.
^ Switch off engine.
^ Press the brake pedal to set a vacuum pressure of not more than 0.8 bar and wait for the value to stabilize.
^ When the brake pedal is not pressed, the vacuum pressure is permitted to drop over a test period of 1 minute by max. 0.06 bar.
If specified values are not reached:
^ Check line connections for vacuum seal.
^ Replace vacuum non-return valve.
^ Check seal between brake booster and brake master cylinder (sealing ring) for perfect condition and correct seating.
^ If the specified values are not achieved when the test is repeated, you must replace the brake booster.