Chevrolet Silverado / GMC Sierra. Manual — part 1897

the front of the engine block and driven directly by the crankshaft sprocket. The pump gears
rotate and draw oil from the oil pan sump through a pick-up screen and pipe. The oil is
pressurized as it passes through the pump and is sent through the engine block lower oil gallery.
Contained within the oil pump assembly is a pressure relief valve that maintains oil pressure
within a specified range.

Pressurized oil is directed through the engine block lower oil gallery to the full flow oil filter
where harmful contaminants are removed. A bypass valve is incorporated into the oil filter, which
permits oil flow in the event the filter becomes restricted. A second valve, the active fuel
management oil pressure relief valve is incorporated into the oil pan. The active fuel management
oil pressure relief valve limits oil pressure directed to the upper oil galleries and valve lifter oil
manifold assembly to 379-517 kPa (55-75 psi) maximum. When main oil pressure exceeds 379
kPa (55 psi), the oil pressure relief valve exhausts excess oil to the sump.

Oil is then directed from the filter to the upper main oil galleries and the valve lifter oil manifold
assembly. Oil from the left upper oil gallery is directed to the crankshaft and camshaft bearings.
Oil that has entered both the upper main oil galleries also pressurizes the valve lifter assemblies
and is then pumped through the pushrods to lubricate the valve rocker arms and valve stems.

An oil passage at camshaft bearing location 2 permits oil flow into the center of the camshaft. Oil
enters the camshaft exiting at the front and into the camshaft position (CMP) actuator solenoid
valve. The CMP valve spool position is controlled by the engine control module (ECM) and
CMP magnet. When commanded by the ECM, the CMP magnet repositions the CMP actuator
solenoid valve spool directing pressurized oil into the CMP actuator to control valve timing.
Refer to Camshaft Actuator System Description .

Oil returning to the pan is directed by the crankshaft oil deflector. The oil pressure sensor is
located at the top rear of the engine. For RPO L99, active fuel management hardware is present
in first design engines. The system is inactive for the 2007 model year. Refer to Cylinder
Deactivation (Active Fuel Management) System Description and Camshaft Position
Actuator and Solenoid Valve Description.

LUBRICATION DESCRIPTION - MAIN PRESSURE BELOW 55 PSI WITH CYLINDER
DEACTIVATION (ACTIVE FUEL MANAGEMENT) ON (RPO LH6/LMG/LY5/LC9)

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