Engine Concerns Resulting from Improper Service

Following the recommended vehicle maintenance schedule is critical to proper engine operation over the life of a vehicle. Performing the required maintenance procedures on all GM vehicles reduces the possibility of engine oil sludge build-up, contamination and/or any other conditions that may result in poor engine performance and internal engine damage.


Vehicles that have a lack of scheduled maintenance, have improper service performed, or have aftermarket calibrations installed are not covered under the new vehicle warranty.


Scheduled Maintenance


There are a number of conditions that will be evident if a vehicle’s recommended maintenance has not been followed.


Oil Filter – An oil filter may be blocked by debris and oil sludge if regular maintenance is neglected. On vehicles equipped with an oil filter cartridge, inspect the cap for sludge. (Fig. 1, #1) Also check the oil filter pleats (Fig. 1, #2) for heavy debris or sludge as well as any holes, tears or signs of improper installation. Check the cap for a missing seal too. (Fig. 1, #3)


F01 maintenance 1

Fig. 1


Oil Pan – Improper maintenance can lead to sludge build-up in the bottom of the oil pan. Sludge or debris in the bottom of the pan (Fig. 2, #1) may block the pick-up tube screen. Some light debris in the oil pump pick-up tube screen should be considered normal. (Fig. 2, #2) Use your judgement to determine what is or what is not considered normal wear.


F02 maintenance 2

Fig. 2


Valve Cover and Camshaft – The valve covers may be blocked at the engine breather, vacuum or oil supply and return ports if regular maintenance has not been performed. Sludge may be seen on the camshaft caps and camshaft. (Fig. 3, #1 and #2) Low oil pressure or a loss of pressure may lead to damage, such as scratches or gouges on the journals or lobes of the camshaft. (Fig. 3, #3) A lack of oil from lack of maintenance also may create a lifter tappet ticking noise. Check for sludge build-up on the camshaft position actuator solenoids (Fig. 4, #2) and debris on the solenoid screen. (Fig. 4, #1)


F03 maintenance 3

Fig. 3

F04 maintenance 4

Fig. 4


Improper Service


The improper service of a vehicle may result in poor engine performance. Also make sure components are properly installed when performing maintenance procedures.


Air Filter – Improper installation of the air filter in the air filter housing or the use of an aftermarket air filter can allow foreign debris (Fig. 5, #2) to bypass the air filter or the air filter housing outlet ducts and enter the combustion chamber. As result, there may be damage to the piston and cylinder wall. (Fig. 5, #1)


F05 maintenance 5Fig. 5


Bearings – Main and rod bearing damage may be caused by foreign debris. Dust and debris on the crankshaft, crankshaft bearings, rods or rod bearings can cause the chrome finish of the journals to prematurely wear (Fig. 6, #1 and #2), increasing clearance and possibly causing low oil pressure or a knocking noise. Scratches on the journals also can lead to a loss of oil pressure.


F06 maintenance 6

Fig. 6


Aftermarket Calibrations


Engine damage may result from incorrect calibrations or other modifications made to the vehicle. Non-GM engine calibrations can be identified using the Tech 2 or GDS 2.


Pistons – Piston damage may be caused by a pre-detonation lean event. (Fig. 7, #1) Improper engine warm-up, such as from aftermarket cold air filters, can create excessive heat to the pistons and cause them to seize to the cold cylinder walls and crack the piston lands. (Fig. 7, #2)


F07 maintenance 7

Fig. 7


– Thanks to Tracy Lucas

Service Know-How
MDI 2 Available through GM Tools and Equipment

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