Hummer H2. Manual - part 1795

Fig. 366: Engine Block Rear Oil Gallery Plug
Courtesy of GENERAL MOTORS CORP. 

8. Remove the engine block rear oil gallery plug.  

9. Inspect the O-ring seal of the rear oil gallery plug. 

If the O-ring seal is not cut or damaged, the plug and O-ring seal may be used during assembly. 

Fig. 367: Engine Block Front Oil Gallery Plug 
Courtesy of GENERAL MOTORS CORP. 

IMPORTANT:

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Remove the front oil gallery plug only if service is required.  

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If the front oil gallery plug is removed, a NEW oil gallery plug must 

 

2004 Hummer H2 

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

  

10. Remove the engine block front oil gallery plug.  

ENGINE BLOCK CLEANING AND INSPECTION 

Tools Required 

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J 8087 Cylinder Bore Gauge. See Special Tools and Equipment .  

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J 42385-100 Thread Repair Kit. See Special Tools and Equipment .  

1. Clean the following areas: 

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The engine block in the solvent, to remove all sludge, dirt, or debris 

Refer to Cleanliness and Care . 

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Dry the block with compressed air.  

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The gasket surfaces 

Refer to Replacing Engine Gaskets . 

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The coolant passages  

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The oil galleries  

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The main bearing caps  

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The engine block cylinder head bolt holes for threadlocking material 

Thread repair driver tool J 42385-107 may be used to clean the threads of old threadlocking 
material. 

2. Inspect the following areas: 

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The cylinder walls for excessive scratches, gouging, or ring ridge  

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The cylinder bores for excessive ring ridge at the top of the cylinder  

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The coolant jacket for cracks  

be installed.  

NOTE:

Do not use a caustic solution to clean the aluminum engine block.

IMPORTANT: When cleaning the engine block in a thermal type oven, do not 

exceed 450°F (232°C).

CAUTION: Refer to Safety Glasses Caution in Cautions and Notices.

 

2004 Hummer H2 

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

  

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The valve lifter bores for excessive scoring or wear  

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The crankshaft bearing webs for cracks  

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The gasket sealing surfaces for excessive scratches or gouging 

Refer to Replacing Engine Gaskets . 

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The oil galleries for restrictions  

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All threaded bolt holes for damage  

3. Measure the following areas: 

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The cylinder bores for taper  

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The cylinder bores for excessive ring ridge at the top of the cylinder  

Measuring the Cylinder for Taper, Out-of-Round, and Oversize 

 

2004 Hummer H2 

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

  

Fig. 368: Measuring J 8087 Dimension
Courtesy of GENERAL MOTORS CORP. 

1. Adjust the micrometer to a dimension slightly smaller than the bore size. 

Adjust the micrometer to 101.62 mm (4.0 in) for 6.0 liter engines. 

Fig. 369: Determining Cylinder Bore Out-Of-Round Using J 8087

 

2004 Hummer H2 

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