Chevrolet Silverado / GMC Sierra. Service manual — part 233

ENGINE NOISE UNDER LOAD

Excessive piston pin-to-bore clearance

1. Inspect the piston, pin, and connecting

rod.

2. Replace the piston and pin as an

assembly, as required.

Excessive connecting rod bearing clearance Inspect the following components and repair,

as required:

The connecting rod bearings

The connecting rods

The crankshaft

The crankshaft journals

Excessive crankshaft bearing clearance

Inspect the following components and repair,

as required:

The crankshaft bearings

The crankshaft journals

Incorrect piston, piston pin, and connecting

rod installation

Pistons must be installed with the mark or

dimple on the top of the piston facing the

front of the engine. Piston pins must be

centered in the connecting rod pin bore.

1. Verify the pistons, piston pins and

connecting rods are installed correctly.

Refer to Piston, Connecting Rod, and

Bearing Installation.

2. Repair, as required.

Cause

Correction

Low oil pressure

1. Perform an oil pressure test. Refer to

Oil Pressure Diagnosis and Testing.

2. Repair or replace, as required.

Detonation or spark knock

Verify the correct operation of the ignition

controls. Refer to Symptoms - Engine

Controls .

Loose torque converter bolts

1. Inspect the torque converter bolts and

flex plate.

2. Repair, as required.

Cracked flex plate - automatic transmission

1. Inspect the flex plate bolts and flex

2008 Hummer H2

2008 ENGINE Engine Mechanical - 6.2L - H2

ENGINE WILL NOT CRANK - CRANKSHAFT WILL NOT ROTATE

plate.

2. Repair, as required.

Excessive connecting rod bearing clearance Inspect the following components and repair,

as required:

The connecting rod bearings

The connecting rods

The crankshaft

Excessive crankshaft bearing clearance

Inspect the following components and repair,

as required:

The crankshaft bearings

The crankshaft journals

The cylinder block crankshaft bearing

bore

Cause

Correction

Seized accessory drive system component

1. Remove the accessory drive belts.

2. Confirm that the engine will rotate.

Rotate the crankshaft by hand at the

crankshaft balancer or flex plate

location.

3. Repair or replace the components, as

required.

Seized automatic transmission torque

converter

1. Remove the torque converter-to-flex

plate bolts.

2. Confirm that the engine will rotate.

Rotate the crankshaft by hand at the

crankshaft balancer or flex plate

location.

3. Repair or replace the components, as

required.

Broken timing chain

1. Inspect the timing chain and sprockets.

2. Repair or replace the components, as

2008 Hummer H2

2008 ENGINE Engine Mechanical - 6.2L - H2

required.

Seized timing chain or timing sprockets

1. Inspect the timing chain and sprockets

for foreign material or a seized chain.

2. Repair or replace the components, as

required.

Seized or broken camshaft

1. Inspect the camshaft and the camshaft

bearings.

2. Repair or replace the components, as

required.

Bent valve in the cylinder head

1. Inspect the valves and the cylinder

heads.

2. Repair or replace the components, as

required.

Seized oil pump

1. Inspect the oil pump assembly.

2. Repair or replace, as required.

Hydraulically locked cylinder

Coolant/antifreeze in the cylinder

Oil in the cylinder

Fuel in the cylinder

1. Remove the spark plugs and inspect for

fluid in the cylinder. When rotating the

engine with the spark plugs removed,

the piston, on compression stroke, will

push fluid from the combustion

chamber. Refer to Coolant in

Combustion Chamber.

2. Inspect for failed/broken head gaskets.

3. Inspect for a cracked engine block or

cylinder head.

4. Inspect for a sticking fuel injector.

5. Repair or replace the components, as

required.

Material in the cylinder

Broken valve

Broken piston rings

Piston material

Foreign material

1. Inspect the cylinder for damaged

components and/or foreign materials.

2. Repair or replace the components, as

required.

Seized crankshaft or connecting rod bearings

1. Inspect crankshaft and connecting rod

2008 Hummer H2

2008 ENGINE Engine Mechanical - 6.2L - H2

COOLANT IN COMBUSTION CHAMBER

bearings.

2. Repair or replace the components, as

required.

Bent or broken connecting rod

1. Inspect the connecting rods.

2. Replace the piston and pin as an

assembly, as required.

Broken crankshaft

1. Inspect the crankshaft.

2. Repair or replace the components, as

required.

Cause

Correction

DEFINITION: Excessive white smoke and/or coolant type odor coming from the exhaust

pipe may indicate coolant in the combustion chamber. Low coolant levels, an inoperative

cooling fan, or a faulty thermostat may lead to an overtemperature condition, which may

cause engine component damage.

1. A slower than normal cranking speed may indicate coolant entering the combustion

chamber. Refer to Engine Will Not Crank - Crankshaft Will Not Rotate.

2. Remove the spark plugs and inspect for spark plugs saturated by coolant or coolant in

the cylinder bore.

3. Inspect by performing a cylinder leak-down test. During this test, excessive air

bubbles within the coolant may indicate a faulty gasket or damaged component.

4. Inspect by performing a cylinder compression test. 2 cylinders side-by-side on the

engine block, with low compression, may indicate a failed cylinder head gasket. Refer

to Engine Compression Test.

Faulty cylinder head gasket

Replace the head gasket and components, as

required. Refer to Cylinder Head Cleaning

and Inspection and Cylinder Head

Replacement - Left Side or Cylinder Head

Replacement - Right Side.

Warped cylinder head

Machine the cylinder head to the proper

flatness, if applicable and replace the cylinder

head gasket. Refer to Cylinder Head

Cleaning and Inspection.

Cracked cylinder head

Replace the cylinder head and gasket.

2008 Hummer H2

2008 ENGINE Engine Mechanical - 6.2L - H2