Brake Booster Vacuum Pump
- Block wheels and apply parking brake. Disconnect low vacuum switch (if equipped). Place automatic transmission in Park or manual transmission in Neutral. Start and run engine at idle. Disconnect vacuum pump hose from brake booster and install vacuum gauge. See Fig 1
.
- Minimum vacuum gauge reading should be 21 in. Hg at sea level, within 30 seconds. For higher altitudes, compensate vacuum reading according to graph. See Fig 1
. If vacuum reading is correct, go to step 4).
Courtesy of FORD MOTOR CO.
- 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 reading is still low, replace vacuum pump. If vacuum pump is now okay, go to next step.
- Reconnect vacuum hose with a "T" fitting 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 correct, remaining problems are not in vacuum system. If vacuum reading is lower than specified, check hoses for leaks and repair as necessary. If vacuum reading is still low, check vacuum accessories for leaks. Repair or replace as necessary.
Courtesy of FORD MOTOR CO.