Vacuum Pump: Testing
- Disconnect vacuum pump-to-brake booster hose at pump and attach vacuum gauge to fitting. Disconnect vacuum outlet hose. Plug hose (DO NOT plug pump fitting). With engine at idle speed (800 RPM), vacuum should be at least 21 in. Hg within 30 seconds.
- If vacuum is low, check gauge and connections for leaks. Check belt tension and idle speed. If reading is still low, replace pump.
- Install a "T" fitting in vacuum hose between pump and brake booster. Attach vacuum gauge at "T". Run engine at idle for about 1 minute. Vacuum should be no more than 3 in. Hg lower than in step 1).
- If vacuum is too low, check gauge and connections for leaks. If reading is still low, check power booster and any vacuum operated accessories for leaks. Repair or replace as needed.