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

Special tools required: 

• 34 3 100

• Pull hose off connection. Install vacuum tester 34 3 100 between connection and vacuum hose on non-return valve.
• Start engine.
• Check buildup of partial vacuum. Switch off engine.
• Press brake pedal to set a partial vacuum of no more than 0.8 bar and wait for value to stabilize.
• When the brake pedal is not pressed, the partial vacuum is allowed to drop by max. 0.06 bar over a test period of 1 minute.
  Fig 1: Checking Brake Booster (Low-Pressure Test)

  

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.