Hummer H3. Manual — part 489

Test Procedure

1. Disconnect the battery ground negative cable.

2. Remove the spark plugs. Refer to Spark Plug Replacement .

3. Rotate the crankshaft to place the piston in the cylinder being tested at top dead center

(TDC) of the compression stroke.

4. Install the J 35667-A , or equivalent.

5. Apply shop air pressure to the J 35667-A and adjust according to the manufacturers

instructions.

6. Record the cylinder leakage value. Cylinder leakage that exceeds 25 percent is considered

excessive and may require component service. In excessive leakage situations, inspect for
the following conditions:

Air leakage noise at the throttle body or air inlet hose that may indicate a worn or
burnt intake valve or a broken valve spring.

Air leakage noise at the exhaust system tailpipe that may indicate a worn or burnt
exhaust valve or a broken valve spring.

Air leakage noise from the crankcase, oil level indicator tube, or oil fill tube that may
indicate worn piston rings, a damaged piston, a worn or scored cylinder bore, a
damaged engine block or a damaged cylinder head.

Air bubbles in the cooling system may indicate a damaged cylinder head or a damaged
cylinder head gasket.

7. Perform the leakage test on the remaining cylinders and record the values.

OIL CONSUMPTION DIAGNOSIS

Cracked or damaged engine block

CAUTION: Refer to Battery Disconnect Caution .

IMPORTANT: It may be necessary to hold the crankshaft balancer bolt to

prevent the crankshaft from rotating.

Checks

Causes

Excessive oil consumption, not due to leaks, is the use of 1 L (1 qt) or more of engine oil
within 3 200 kilometers (2,000 miles).

2008 Hummer H3

2008 ENGINE Engine Mechanical - 5.3L - H3

Preliminary

The causes of excessive oil consumption may include the
following conditions:

External oil leaks

Refer to Oil Leak Diagnosis.

Incorrect oil level or improper reading of the oil level
indicator

With the vehicle on a level surface, run the engine for a
few minutes, allow adequate drain down time, 2-3
minutes, and measure for the correct engine oil level.

Improper oil viscosity

Refer to the vehicle owners manual and use the
recommended SAE grade and viscosity for the prevailing
temperatures.

Continuous high speed driving and/or severe usage

Crankcase ventilation system restrictions or
malfunctioning components

Refer to Crankcase Ventilation System
Inspection/Diagnosis.

Worn valve guides and/or valve stems

Worn or improperly installed valve stem oil seals

Refer to Spark Plug Inspection .

Piston rings broken, worn, or not seated properly

Allow adequate time for the rings to seat.

Replace worn piston rings, as necessary.

Refer to Cylinder Leakage Test.

Piston and rings improperly installed or not fitted to the

2008 Hummer H3

2008 ENGINE Engine Mechanical - 5.3L - H3

OIL PRESSURE DIAGNOSIS AND TESTING

Tools Required

EN-47971 Oil Pressure Gage Adapter. See Special Tools.

J 21867 Pressure Gage

Test Procedure

cylinder bore

Refer to Lower Engine Noise, Regardless of Engine
Speed.

2008 Hummer H3

2008 ENGINE Engine Mechanical - 5.3L - H3

Fig. 14: View Of Special Tools Oil Pressure Gage & Adapter
Courtesy of GENERAL MOTORS CORP.

1. With the vehicle on a level surface, run the vehicle for a few minutes. Allow adequate drain

down time, 2-3 minutes, and measure the oil level.

2. If required, add the recommended grade engine oil and fill the crankcase until the oil level

measures full on the oil level indicator.

3. Run the engine briefly, 10-15 seconds, and verify low or no oil pressure on the vehicle gage

or light.

4. Listen for a noisy valve train or a knocking noise.

2008 Hummer H3

2008 ENGINE Engine Mechanical - 5.3L - H3