Hummer H1 Service Manual page 51

_____________________________________________________________________
2-14 Engine
PROBLEM
Overheating 5.
(continued)
6.
7.
8.
9.
10. Coolant temperature gauge or sensor faulty.
High Fuel 1. Prolonged high speed - high load operation.
Consumption
2. Air cleaner/Þlter partially plugged.
3. Fuel leaks in lines, hoses at connections.
4. Restriction in exhaust system (should also be
accompanied by drop in power).
5. Decrease in boost on turbocharged models,
caused by vacuum leak at actuator, manifold
leak, or turbo damage.
6. Brake drag
7. Converter one way clutch failure.
8. Injection pump internal problem.
9. Power loss due to worn rings, valve guides,
cylinder bores, valves, etc.
POTENTIAL CAUSE
Failed thermostat or radiator cap.
Fan clutch inoperative.
Water pump inoperative.
Blown head gasket.
Crack in block, or leaking freeze plug.
Engine Diagnosis
5. Check thermostat and cap operation. Replace
either part if inoperative.
6. Replace clutch.
7. Check coolant ßow and replace pump if necessary.
8. Verify that coolant is leaking into combustion
chamber and replace gasket.
9. Replace corroded freeze plugs. Replace block if
cracked.
10. Test and replace gauges or sensors as needed.
1. Normal with this type of operation. Have driver
reduce speed or load if possible.
2. Remove and clean air horn, intake hose, air
cleaner. Replace Þlter.
3. Locate and repair as needed.
4. Inspect and replace bent, kinked, damaged compo-
nents.
5. Correct leaks. Replace actuator or turbocharger if
inoperative.
6. Repair stuck/seized calipers.
7. Replace converter.
8. Diagnose and replace as necessary.
9. Overhaul engine.
CORRECTION
¨