PIP5163A

Bulletin No.: PIP5163A
Date: Jul-2014
Subject:
Alleged Cylinders Out Of Round
Models:
2015 and Prior GM Passenger Cars and Trucks
This PI was superseded to update Model Years. Please discard PIP5163.
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern
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.
Note: GM has not had an issue with cylinders being machined out of round for any engine family in recent history.
The peak to valley spec for crosshatch is .65-2.8 microns. Any deviation and the crosshatch will be gone.
Even if a cylinder is suspected of being oversize we can only confirm that by checking with an air gage at the engine plant.
Recommendation/Instructions
When inspecting the engine block to determine if the cylinder bores are good,
Look for the following:
1.
Cylinder damage or scoring- the cylinder walls will contain grooves deep enough to catch with a finger nail.
2.
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 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. The crosshatch will be faint and there will not be sharpness. At high mileage this should be an insurance claim if the
air filtering system has been opened numerous times for service in dusty climates.
4.
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. Back cylinders go first if caught early. Otherwise there will be no Crosshatch and the engine will need to be
replaced.
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Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the
remaining steps do not need to be performed.
GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may
occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools,
safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that
your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.
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