Power Brake Booster Vacuum Test
- Connect vacuum gauge to booster check valve with short length of hose and T-fitting. See Fig 1.
- Start and run engine at idle speed for one minute.
- Observe the vacuum supply. If vacuum supply is not adequate, repair vacuum supply.
- Clamp hose shut between vacuum source and check valve.
- Stop engine and observe vacuum gauge.
- If vacuum drops more than one in. Hg (33 millibars) within 15 seconds, booster diaphragm or check valve is faulty.
Courtesy of DAIMLERCHRYSLER CORP.