Manufacturer communication — 2006 GMC YUKON DENALI XL

• Applies to all models and engines, 2000 - 2018.

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  All All 2000 - 2018 All All All All

• An engine block is suspected of cylinder bore damage, scoring or out of round as the cause of oil consumption, misfire, cylinder leakage or blow by.

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  Suspecting an engine block of possible cylinder bore damage, scoring or out of round as the possible cause of engine oil consumption, misfire, cylinder leakage or blow by.

Steps to confirm (in the document’s order)

1. Cylinder damage or scoring: the cylinder walls have grooves deep enough to catch with a finger nail.

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   1. Cylinder damage or scoring- the cylinder walls will contain grooves deep enough to catch with a finger nail.

2. An out of round bore has areas where the cross hatch is missing or worn; if there is crosshatch all the way around the bore from top to bottom, the bore is not out of round.

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   An out of round cylinder bore- will contain areas where the cross hatch is missing or worn from different section of the cylinder bore. If there is crosshatch all the way around the bore from top to bottom the cylinder bore is not out of round.

3. Dirt intrusion: if the air filtering system was compromised the engine wears out very quickly; grit is found in the intake runners and the bores look lightly sand blasted.

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   Dirt intrusion- If the filtering system has been compromised the engine will wear out very quickly. You will find grit in the intake Runners and the cylinder bores will look lightly sand blasted.

4. Catalytic converter failure: if the brick is broken the dust can be drawn back into the engine, and the bores look sand blasted.

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   Catalytic Converter failure- If a converter fails and the brick is broken, the dust can be drawn back into the engine. A block showing this type of failure, will have bores that look to be sand blasted.

Repair

• With converter dust the back cylinders go first if caught early; otherwise there is no crosshatch left and the engine needs to be replaced.

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  Back cylinders go first if caught early. Otherwise there will be no Crosshatch and the engine will need to be replaced.

Caution

• GM has not had an issue with cylinders machined out of round for any engine family in recent history.

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  GM has not had an issue with cylinders being machined out of round for any engine family in recent history.

• An oversize cylinder can only be confirmed by checking with an air gauge at the engine plant.

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  Even if a cylinder is suspected of being oversize we can only confirm that by checking with an air gauge at the engine plant.