Manufacturer communication — 2006 GMC YUKON DENALI XL

• 2016 and prior GM passenger cars and trucks.

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  Models: 2016 and Prior GM Passenger Cars and Trucks

• When an engine is replaced because of internal damage, extreme care is needed when transferring the intake manifold to the new Genuine GM service engine long block.

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  When replacing an engine due to internal damage, extreme care should be taken when transferring the intake manifold to the new Genuine GM Part service engine long block.

• Ingested catalytic converter material causes heavy wear to piston rings and cylinder walls, with misfires and oil consumption as the result.

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  Any such material transfer can cause heavy wear to piston rings and cylinder walls. Misfires and oil consumption are the by products of ingested catalytic converter material into the combustion chamber and cylinder bores.

Possible causes

• The internal damage may have discharged engine component debris into the intake manifold through broken pistons and/or bent, broken or missing intake valves.

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  The internal engine damage may have resulted in the potential discharge of internal engine component debris into the intake manifold via broken pistons and/or bent, broken, or missing intake valves.

• Replacement is required because the complex inlet runner and plenum configuration makes thorough cleaning difficult and complete removal of debris nearly impossible to verify.

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  This replacement is required due to the complex inlet runner and plenum configuration of most of the intake manifolds, making thorough and complete component cleaning difficult and nearly impossible to verify the complete removal of debris.

• When a catalytic converter fails and the plugged inner brick breaks apart, converter material can be sucked back into the engine during valve overlap and spread through the intake manifold into the cylinder.

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  When catalytic converter failures occur and the inner brick becomes plugged and breaks apart, the catalytic converter material can be sucked back into the engine during valve overlap and transfer throughout the intake manifold and into the cylinder.

Steps to confirm (in the document’s order)

• After removing the intake manifold, inspect all cylinder head intake ports to see whether the valve heads are still present and not bent.

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  After removing the intake manifold from the engine, the technician MUST carefully inspect all of the cylinder head intake ports to see if the valve heads are still present and not bent.

Repair

1. If debris is present in any of the cylinder head intake ports, the intake manifold should be replaced.

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   If this debris is present in ANY of the cylinder head intake ports, the intake manifold should be replaced.

2. After broken valves, broken pistons or piston to cylinder head damage, the intake manifold must be replaced or subsequent severe engine damage will occur.

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   Broken valves, broken pistons and piston to cylinder head damage all create material debris that scatters throughout the induction system. ⇒If ANY of the above were to occur, the intake manifold MUST be replaced or subsequent severe engine damage will occur.

Caution

• Reinstalling an intake manifold taken from an engine with debris deposits may let remaining debris be ingested into the new service engine.

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  Reinstallation of an intake manifold removed from an engine with deposits of internal engine component debris may result in the ingestion of any remaining debris into the new Genuine GM Part service engine.

• The plastic intake manifold cannot be disassembled.

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  Notice: The plastic intake manifold CANNOT be disassembled.