Thursday, July 20, 2017 Detailed Auto Topics
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It is no secret to many GM truck owners that oil consumption is a problem. "This is normal," is often the excuse. A technical service bulletin seems to suggest GM may be softening on their previous position and offering a bit of help with a few models.

Few owners may consider that using a quart of oil every thousand miles is normal. After all sorts of excuses, GM may be acknowledging the problem, at least on some engines.

GM covers which vehicles under warranty?

Technical service bulletin 10-06-01-0081, dated February 19, 2013, pertains to oil consumption on some active fuel management or AFM equipped vehicles. Among these are the following, but they do not include all engine types and sizes.

 Eligible Vehicles

2007 - 2011 Cadillac Escalade

2007 - 2011 Chevrolet Avalanche, Silverado 1500, Suburban, Tahoe

2010 - 2011 Chevrolet Camaro

2007 - 2011 GMC Sierra 1500, Sierra Denali, Yukon

2008 - 2009 Pontiac G8 GT

Built prior to February 1, 2011

GM now states, burning more than one quart of oil in two to three thousand miles is unacceptable. Customers owning the models covered may get no-charge repair, if they are still in the five-year/100,000 mile power-train warranties. Beyond five years and 100,000 miles, the bulletin is for information only and warranties do not apply. Many owners may still benefit from the updates, though they have to pay for them. Any independent shop can check for the problem and make the repairs, out of the warranty.

The left valve cover

A revised left valve cover may help

They have revised the left valve cover for engines built prior to February 1, 2011. The original design may allow oil to pass from the cover to the engine intake. Once in the intake, the oil burns in the engine.

 

Oil puddling in intake is evidence of problem

They redesigned the left valve cover to help prevent the PCV system from drawing oil from the engine. We check for the condition by removing the throttle body and looking inside the intake manifold. A normal system will have an oil film, but no puddling of oil in the intake. Where excess oil is found in the intake, we replace the left valve cover with the appropriate revised model. The covers are year-specific and are not interchangeable.

The AFM valve shield

GM also states, on some models, built prior to October 1, 2010, the active fuel management or AFM valve can spray excess oil in the crankcase. This oil flow may cause the piston rings to stick and drastically increase oil consumption.

The active fuel management valve

A valve in the oil pan allows oil to return from the valve lifters, when active fuel management operates. This valve is inside the oil pan, near the oil filter base.

A shield diverts the discharge oil from piston rings

Removing the oil pan allows access to the AFM valve. We remove the valve and install a small shield to divert oil from the piston ring area. Engines built after October 1, 2010 should already have the shield and will not benefit.

Stuck piston rings

The engineers at GM also outline a cleaning procedure that may help with sticking piston rings. We remove the spark plugs and a cleaner (GM P/N 88861803) is added to each cylinder. The cleaner remains in the cylinder 2.5 to three hours. Cranking the engine over without the spark plugs pushes the cleaner out when finished. We should also disable the fuel injectors and ignition when using the procedure, to prevent fire hazards.

GM also suggests that some pistons may be on the high side of specifications when manufactured. If cleaning does not help, they may cover replacement of the pistons and rings, under the powertrain warranty.

More than five years or 100,000 miles, the owner is responsible for repair and would need to consider if piston and ring replacement is feasible.





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