Manufacturer communication — 2006 GMC YUKON DENALI XL

• Applies to 2016 and prior GM passenger cars and trucks.

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  2016 and Prior GM Passenger Cars and Trucks

Possible causes

• Broken pistons and/or bent, broken or missing intake valves may have discharged engine debris into the intake manifold.

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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.

• The complex runner and plenum shape of most intake manifolds makes thorough cleaning difficult and complete debris removal 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.

Steps to confirm (in the document’s order)

1. 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.

2. When valve heads are missing or sufficiently bent, engine debris is usually present to varying degrees in the intake port of the cylinder head.

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   Usually when the valve heads are missing or sufficiently bent, internal engine component debris will be present to varying degrees in the intake port of the cylinder head.

Repair

• If debris is present in any cylinder head intake port, replace the intake manifold.

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

Caution

• When an engine is replaced for internal damage, take extreme care when transferring the intake manifold to the new 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.

• Reinstalling a 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.