Hummer H3. Manual — part 206

Fig. 448: Checking For Cylinder Head Warpage
Courtesy of GENERAL MOTORS CORP.

2. If the gasket failed, determine the cause. The following conditions may cause gasket failure:

Improper installation

Warped cylinder head

Missing or not fully seated dowel pins

Low torque on the cylinder head bolts

Incorrect length cylinder head bolts

A warped engine block surface

Scratched surfaces

Foreign material

2006 Hummer H3

2006 ENGINE Engine Mechanical - 3.5L (L52) - H3

Cracked engine block threaded holes

3. Clean the following components:

The gasket surfaces

Do not use a motorized brush on the head gasket sealing surface.

Valve stems and valve heads

The bolt hole threads

Remove all dirt, debris, or threadlocking material from the bolt holes.

4. Inspect the cylinder head mating surfaces for flatness. Use a feeler gauge and a straight edge.

5. Replace the cylinder head if warped more than 0.08 mm (0.003 in).

6. Inspect the cylinder head for cracks.

7. Inspect the cylinder head deck for corrosion.

IMPORTANT: Do not attempt to weld the cylinder head. If the cylinder head

is damaged, replace the cylinder head. Minor nicks may be
repaired with a fine flat file or emery cloth.

2006 Hummer H3

2006 ENGINE Engine Mechanical - 3.5L (L52) - H3

Fig. 449: Measuring Valve Spring Tension
Courtesy of GENERAL MOTORS CORP.

8. Inspect the valve springs for squareness.

9. Use J 9666 to measure the valve spring tension. Replace the valve spring if the tension is not

within specification.

2006 Hummer H3

2006 ENGINE Engine Mechanical - 3.5L (L52) - H3

Fig. 450: Inspecting Valve Guides
Courtesy of GENERAL MOTORS CORP.

10. Inspect the valve guides for wear. The valve guides may be reamed oversized 0.075 mm

(0.003 in) and oversized stemmed valves may be installed. The same size valve seal should
be used.

11. Inspect the valve seats for excessive wear, damage, or hot spots.

12. Use the following procedure to measure the valve seat concentricity:

2006 Hummer H3

2006 ENGINE Engine Mechanical - 3.5L (L52) - H3