Diagnosis & Testing
- Block wheels, apply parking brake and place auto. trans. in "PARK", man. trans. in "NEUTRAL". Disconnect vacuum pump hose from brake booster and install a vacuum gauge. See Fig 1 .
- See Fig 1 . Disconnect outlet hose from outlet tube on pump and plug end of hose, if used. Do NOT plug outlet tube with engine idling.
- Minimum vacuum reading should be 21 in. Hg at sea level, within 30 seconds. If vehicle is at other than sea level, compensate vacuum reading according to graph. See Fig 1 .
- If vacuum pump checks okay, go to step 5). If vacuum reading is low or fluctuating, check gauge and connections for leaks. If pump is belt driven, check belt tension and pulley fit to shaft. Check idle speed. Recheck vacuum pump. If vacuum checks okay, go to step 5). If vacuum reading is still low, replace vacuum pump.
- Remove plug from outlet hose and reconnect hose to pump outlet tube, if used. Reconnect vacuum hose with a "TEE" and vacuum gauge located near pump inlet. See Fig 2 . With engine idling, vacuum may be 3 in. Hg less than that measured in step 1).
- If vacuum reading is okay, remaining problems are not in vacuum system. If vacuum reading is lower than specified, check all attaching hoses for leaks and repair as necessary. If vacuum reading is still low, check all vacuum accessories for leaks. Repair or replace as necessary.