Replace Intake Gasket To Fix P0101 And P0300 Codes?

lunytnz · May 27, 2009

Having been getting P0101 (MAF) and PO300 (Random Misfire) codes, intermittently, for months, I noticed I could smell coolant recently. I talked to a service guy at the dealership who suggested that it was probably the intake manifold gasket and said it was a common problem with the 5.7L with 100K+ miles. He suggested a leak test to confirm.

Has anyone had a leak test done? Just wondering how it's done and how confident you can be in the results (i.e., pinpointing the problem).

I've read other posts that have said the fix for the P0300 and P0101 codes was replacing the intake gasket. At first, I thought it was extreme, but maybe that's the real problem. The codes typically show up on freeway trips when climbing a hill at 2500+ RPM for a few minutes. So, it could make sense that air is getting in downstream of the MAF.

Has anyone else had to replace the intake manifold gasket to fix this problem?

rodram · May 27, 2009

Having been getting P0101 (MAF) and PO300 (Random Misfire) codes, intermittently, for months, I noticed I could smell coolant recently. I talked to a service guy at the dealership who suggested that it was probably the intake manifold gasket and said it was a common problem with the 5.7L with 100K+ miles. He suggested a leak test to confirm.

Has anyone had a leak test done? Just wondering how it's done and how confident you can be in the results (i.e., pinpointing the problem).

I've read other posts that have said the fix for the P0300 and P0101 codes was replacing the intake gasket. At first, I thought it was extreme, but maybe that's the real problem. The codes typically show up on freeway trips when climbing a hill at 2500+ RPM for a few minutes. So, it could make sense that air is getting in downstream of the MAF.

Has anyone else had to replace the intake manifold gasket to fix this problem?

I had intake manifold gasket replaced in my 97 C2500 5.7L vortec with 200,000 km .... " common problem" is exactly right .. I never checked or saw any codes for this.... took it to my mechanic when I could smell coolant everytime I parked in my garage... only saw a drip of coolant once in a while pn the garage floor.... he tested it and said it needed intake manifold gasket.... the coolant will leak and collect on the top of the engine, then mostly evaporate when you are driving,,,

DONOT use GM gasket for the repair... use a FelPro gasket kit, if you only want to fix it once....

don't delay getting it fixed as it will eventually progress into a coolant leak into your crankcase oil ,,,, and then toast your bearings.....

Westlotorn · December 17, 2009

The GM Vortech family of engines all use a plastic intake manifold. These use very low clamp force on the intake manifold bolts, 11-14 pounds torque. The gasket is special and makes this work with few problems.

Rod R is right on on this one.

The gasket on the GM 1996 to 1999 Vortec is plastic with a rubberized silicone insert for the sealing surface. The Plastic is affected by long life antifreeze and typically fails after several years use. Old antifreeze will eat the plastic. Usually the leaking antifreeze is seen at the front corners of the intake manifold. This is a very common issue with these GM engines.

Fel-Pro actually came up with an improved gasket using a steel carrier rather than plastic, really nice piece that is a life of the engine replacement. Costs about double though. The factory type gasket is available too but if it was me I would step up and install the Fel-Pro, MS98000T for the 5.0L and 5.7L. They also have one for the 4.3L but I don't have the part number handy.

The job took me about 4 hours with no rushing. I wanted to check and clean everything while I was in there.

FYI, the MS 98000T comes with all the gaskets necessary to fix a manifold leak including one valve cover gasket. They said only one side because that is all a shop manual says to remove to get the clearance to take off the manifold. If you don't take off one of the valve covers you will break either the valve cover or the manifold trying to get it off.

Follow the recommended torque sequence, over torque will distort the plastic manifold and cause more issues. Make sure you use a Thread lock to keep the bolts tight.

Hope this helps someone else.