Hummer H2. Manual - part 1888

Fig. 695: Lubrication Flow 
Courtesy of GENERAL MOTORS CORP. 

Engine lubrication is supplied by a gerotor type oil pump assembly. The pump is mounted on 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 oil galleries. 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 lower gallery to the full 
flow oil filter where harmful contaminants are removed. A bypass valve is incorporated into the oil pan, at the 
oil filter boss, which will permit oil flow in the event the filter becomes restricted. At the rear of the block, oil is 
then directed to the upper main oil galleries which are drilled just above the camshaft assembly. From there oil 
is then directed to the crankshaft and camshaft bearings. Oil that has entered 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. Oil returning to the pan is directed by the crankshaft oil deflector. Oil pressure and 
crankcase level are each monitored by individual sensors.

 

2004 Hummer H2 

2004 ENGINE Engine Mechanical - 4.8L, 5.3L, and 6.0L - Hummer H2

  

An external oil cooler is available on certain applications, all 6.0L. Oil is directed from the oil pump, through 
the lower main oil gallery to the full flow oil filter. Oil is then directed through the oil pan outlet oil gallery, 
located in the left rear of the oil pan, and to the external oil cooler via a hose assembly. Oil flows through the oil 
cooler and returns to the engine at the oil pan inlet oil gallery, located in the left rear of the oil pan. Oil is then 
directed to the upper main oil galleries and the remainder of the engine assembly. 

Fig. 696: Oil Pump Assembly 
Courtesy of GENERAL MOTORS CORP. 

Callouts For Fig. 696 

CLEANLINESS AND CARE 

Callout

Component Name

408

Cover Bolt

409

Cover

410

Drive Gear

412

Driven Gear

413

Oil Pump

414

Pressure Relief Valve

415

Pressure Relief Valve Spring

416

Plug

 

2004 Hummer H2 

2004 ENGINE Engine Mechanical - 4.8L, 5.3L, and 6.0L - Hummer H2

  

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Throughout this section, it should be understood that proper cleaning and protection of machined surfaces 
and friction areas is part of the repair procedure. This is considered standard shop practice even if not 
specifically stated.  

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When any internal engine parts are serviced, care and cleanliness is important.  

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When components are removed for service, they should be marked, organized or retained in a specific 
order for assembly. Refer to Separating Parts .  

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At the time of installation, components should be installed in the same location and with the same mating 
surface as when removed.  

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An automobile engine is a combination of many machined, honed, polished and lapped surfaces with 
tolerances that are measured in millimeters or thousandths of an inch. These surfaces should be covered 
or protected to avoid component damage.  

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A liberal coating of clean engine oil should be applied to friction areas during assembly.  

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Proper lubrication will protect and lubricate friction surfaces during initial operation.  

SEPARATING PARTS 

Separate, mark, or organize the following components: 

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Piston and the piston pin  

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Piston to the specific cylinder bore  

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Piston rings to the piston  

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Connecting rod to the crankshaft journal  

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Connecting rod to the bearing cap 

A paint stick or etching/engraving type tool are recommended. Stamping the connecting rod or cap near 
the bearing bore may affect component geometry. 

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Crankshaft main and connecting rod bearings  

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Camshaft and valve lifters  

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Valve lifters, lifter guides, pushrods and rocker arm assemblies  

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Valve to the valve guide  

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Valve spring and shim to the cylinder head location 

IMPORTANT:

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Disassembly of the piston, press fit design piston pin, and connecting rod 
may create scoring or damage to the piston pin and piston pin bore. If the 
piston, pin, and connecting rod have been disassembled, replace the 
components as an assembly.  

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Many internal engine components will develop specific wear patterns on 
their friction surfaces.  

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When disassembling the engine, internal components MUST be 
separated, marked, or organized in a way to ensure installation to their 
original location and position.  

 

2004 Hummer H2 

2004 ENGINE Engine Mechanical - 4.8L, 5.3L, and 6.0L - Hummer H2

  

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Engine block main bearing cap location and direction  

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Oil pump drive and driven gears  

REPLACING ENGINE GASKETS 

Tools Required 

J 28410 Gasket Remover. See Special Tools and Equipment . 

Gasket Use and Applying Sealants 

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Do not use any gasket again unless specified.  

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Gaskets that can be used again will be identified in the service procedure.  

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Do not apply sealant to any gasket or sealing surface unless called out in the service information.  

Separating Components 

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Use a rubber mallet to separate components.  

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Bump the part sideways to loosen the components.  

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Bumping should be done at bends or reinforced areas to prevent distortion of parts.  

Cleaning Gasket Surfaces 

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Remove all gasket and sealing material from the part using the J 28410 or equivalent. See Special Tools 
and Equipment .  

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Care must be used to avoid gouging or scraping the sealing surfaces.  

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Do not use any other method or technique to remove sealant or gasket material from a part.  

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Do not use abrasive pads, sand paper, or power tools to clean the gasket surfaces. 

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These methods of cleaning can cause damage to the component sealing surfaces.  

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Abrasive pads also produce a fine grit that the oil filter cannot remove from the oil.  

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This grit is abrasive and has been known to cause internal engine damage.  

Assembling Components 

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When assembling components, use only the sealant specified or equivalent in the service procedure.  

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Sealing surfaces should be clean and free of debris or oil.  

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Specific components such as crankshaft oil seals or valve stem oil seals may require lubrication during 
assembly.  

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Components requiring lubrication will be identified in the service procedure.  

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When applying sealant to a component, apply the amount specified in the service procedure. 

NOTE:

Refer to Sealant Notice in Cautions and Notices.

 

2004 Hummer H2 

2004 ENGINE Engine Mechanical - 4.8L, 5.3L, and 6.0L - Hummer H2