Chevrolet Silverado / GMC Sierra. Manual — part 1880
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
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).
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
2008 Chevrolet Silverado 1500
2008 ENGINE Engine Mechanical - 4.8L, 5.3L, 6.0L, 6.2L, or 7.0L - Cab & Chassis Sierra, Cab & Chassis Silverado,
Sierra & Silverado
OIL PRESSURE DIAGNOSIS AND TESTING
Tools Required
EN-47971 Oil Pressure Gage Adapter. See Special Tools.
J 21867 Pressure Gage. See Special Tools.
Diagnosis and Testing
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
Worn valve guides and/or valve stems
Worn or improperly installed valve stem oil seals
Piston rings broken, worn, or not seated properly
Allow adequate time for the rings to seat.
Replace worn piston rings, as necessary.
Piston and rings improperly installed or not fitted to the
cylinder bore
2008 Chevrolet Silverado 1500
2008 ENGINE Engine Mechanical - 4.8L, 5.3L, 6.0L, 6.2L, or 7.0L - Cab & Chassis Sierra, Cab & Chassis Silverado,
Sierra & Silverado
Fig. 18: 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 Chevrolet Silverado 1500
2008 ENGINE Engine Mechanical - 4.8L, 5.3L, 6.0L, 6.2L, or 7.0L - Cab & Chassis Sierra, Cab & Chassis Silverado,
Sierra & Silverado
5. Inspect for the following conditions:
Oil diluted by water or glycol antifreeze
Refer to Coolant in Engine Oil .
Foamy oil, which may be caused by a cut or damaged oil pump screen O-ring seal
6. Remove the oil filter and install the EN-47971 (1). See Special Tools.
7. Install the J 21867 (2), or equivalent to the EN-47971 (1). See Special Tools.
8. Run the engine and measure the engine oil pressure.
9. Compare the readings to Engine Mechanical Specifications (RPO LY5 VIN J) or
Engine Mechanical Specifications (RPO LC9 VIN 3) or Engine Mechanical
Specifications (RPO LY2 VIN C) or Engine Mechanical Specifications (RPO LH6
VIN M) or
Engine Mechanical Specifications (RPO LMG VIN 0)
or Engine
Mechanical Specifications (RPO LY6 VIN K) or Engine Mechanical Specifications
(RPO L76 VIN Y) or Engine Mechanical Specifications (RPO L92 VIN 8).
10. If the engine oil pressure is below specifications, inspect the engine for 1 or more of the
following conditions:
Oil pump worn or dirty
Refer to Oil Pump Cleaning and Inspection .
Oil pump-to-engine block bolts loose
Refer to Oil Pump, Screen and Crankshaft Oil Deflector Installation (RPO
LY2/LH6/LMG/LY5/LC9) Oil Pump, Screen and Crankshaft Oil Deflector
Installation (RPO LY6/L76/L92) .
Oil pump screen loose, plugged, or damaged
Oil pump screen O-ring seal missing or damaged
Malfunctioning oil pump pressure relief valve
Excessive bearing clearance
Cracked, porous, or restricted oil galleries
Oil gallery plugs missing or incorrectly installed
Refer to Engine Block Plug Installation .
Improper operation of the active fuel management oil pressure relief valve
2008 Chevrolet Silverado 1500
2008 ENGINE Engine Mechanical - 4.8L, 5.3L, 6.0L, 6.2L, or 7.0L - Cab & Chassis Sierra, Cab & Chassis Silverado,
Sierra & Silverado
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