DESCRIPTION
Vehicles equipped with 6.2L Diesel engines use vacuum pumps to assist in maintaining a proper vacuum level for accessories. This is accomplished by using either belt driven or gear driven mechanical-type pumps.
BELT DRIVEN PUMP
The belt driven pump is a diaphragm-type that requires a belt adjustment at regular intervals. It is driven by alternator belt.
GEAR DRIVEN PUMP
The gear driven pump is a diaphragm-type pump driven by a cam inside drive housing assembly to which it mounts. The drive housing assembly has a drive gear on lower end that meshes with camshaft gear in engine. This drive gear causes cam in drive housing to rotate. The drive gear also powers engine oil pump.
Scheme 73
- Block wheels, apply parking brake and place transmission in Park (A/T) or Neutral (M/T).
- Connect vacuum gauge to pump inlet. (Scheme 73) 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. For higher altitudes, compensate vacuum reading according to graph. (Scheme 73) (Scheme 73): Vacuum Pump Diagnosis
- 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 reading is still low, replace vacuum pump. If vacuum checks okay, go to next step.
- 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. (Scheme 74) 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 hoses for leaks and repair as necessary. If vacuum reading is still low, check vacuum accessories for leaks. Repair or replace as necessary.
Vehicle Vacuum System Diagnosis. Scheme 74
REMOVAL & INSTALLATION
Note. Vacuum pump is serviced as a unit.
Removal & Installation ("C", "G" & "K" Series)
Disconnect battery negative cable. Drain coolant. Remove windshield wiper reservoir. Remove coolant reservoir and hose. Loosen alternator belt and remove pump attaching bolts. Raise and support vehicle. Remove lower radiator hose. Disconnect vacuum hose. Remove lower pump bolt and vacuum pump. To install, reverse removal procedure.
Note. DO NOT run engine without vacuum pump installed. Since the oil pump is powered by the vacuum pump drive gear, no oil would circulate through the engine. The engine could be damaged.
Remove vacuum hose from pump inlet. Remove bolt and bracket holding drive assembly to engine block. Lift pump and drive assembly out of vehicle. Cover hole to prevent foreign materials from falling into engine. To install, reverse removal procedure.