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Pontiac Repair/2002 GP 3.8 NA - Oil in Intake



I just replaced the upper and lower intake gaskets on my 3.8 GP.
I noticed that oil was pooling on top of the lower intake.  There is also lots of oily carbon deposits inside the runners and main pleneum of the upper intake.  

There is no sign of coolant leaking into the manifolds.  My leak was external and affected the lower intake only.  I cleaned everthing before installing the gaskets.  

When I pulled the PCV valve out, there is evidence of oil collecting in the valve socket after just a few days.  
The o-ring on the valve is O/K and the valve fits snuggly into the socket.  The oil seems to be comming though the valve.

Any ideas???


ANSWER: Hi Colin:

that is normal that lowe portion of the inatke is the low spot for the pcv system so that is a normal condition nothing to worry about. if you worried about deposits on the Valves you can run a product called top engine cleaner though a vacuum hose while the car is running and it will clean some of that off. You can get that at any GM dealer. use only top brand name oil in this youi can avoid synthetic those engine drink syntehetic oil. conventinal oil is good enough. also get a bottle of Chevron Techron fuel system cleaner that stuff works wounders. follow the directions on the bottle. one last thing do a google search for "top tier fuel" and use only one of the brands listed. One last thing back to the PCV valve if you change it use only a GM AC DELCO valve and there is an o-ring under the vlave make sure you take it off the old valve and swap it to the new one or you will have driveability issues and for sure an oil consumption issue as well.
good luck :-}

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QUESTION: Thanks for the advice Todd.
I still an concerned that so much oil/carbon deposits are collecting on the inside surface of the upper intake and the back-side of the throttle plate.

Why is the oil vapour backing up into the upper portion on the intake system all the way to the throttle plate?  Doesn't seem right.

as I stated before it's completely normal. it's the gases from the crank case as the combustion leaks past the rings (normal) it pushes minute amount of pressure into the crank case and the oil puddles up in the intake. the cheaper the oil you use the more this will happen. the breather system which is part of the PCV system is part of that also and that is why the throttle plate carbon up. COMPLETELY NORMAL. I have had hundreds of these engines apart and ever one that comes apart there is oil pooled up in the intake that part that you see in not exposed to the runner going to to the cylinders that is blocked off by the upper intake gasket. In essence what you see is the upper portion of the crank case. that is why the upper intake has that big long candy cane looking plastic straw on the back under side of it under the PCV valve that is where it sucks up the crank case gasses.

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Todd Puccio


General auto repair,electrical issues,driveability issues,anti-lock brakes,SIR systems,HVAC,engine performance,Gm specific. I have worked at my current dealership since the 1990 model year anything much older than that I have limited exposure to. I do not have very much transmission experience so those question you may want to ask of another expert. When you send me a question let me know the exact make/model/engine and year for the car or suv you have it makes it easier to answer the questions that way. If your happy with the answer I gave you please feel free to Donate. This is a free service to you and I am not compensated at all by this web site. I have 22 years of experience to share with you and my knowledge wasn't free to me. I had to pay for my education.


Experience in the area: I have been a technician in GM dealerships for over 22 years and I am a ASE master technician. I work at a Buick and GMC truck store Previously I worked at a Pontiac GMC store for 18 years. I Served a a lead technician when dealership was on a team system. I just recently moved to a Buick,Hummer,Saab Store when my franchise was purchased by this dealership. Organizations: ASE master technician


Education/Credentials:High school diploma,2 year vocational school degree 2 year college degree. Associates degree in applied sciences (auto technology)Awards and Honors: GMC master technician

Awards and Honors
Master GMC truck technician Master ASE technician in 9 categories

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