2006 Pontiac Grand Prix

Stuart · Feb 18, 2023

I have a 2006 Pontiac Grand Prix with the 3.8 V6. 235K
miles. It started burning oil and I was finding snot on
the underside of the oil fill cap. So installed a new PCV
valve and changed the oil. I run Mobil 1 synthetic and
change the oil every 5k which is about every 10 weeks.
I checked the underside of the oil fill cap and it had
yellow snot on it again. Remived the pcv valve and it
was full of yellow snot again after only a week or 500
ish miles. Car runs great, has good power and mileage.

Any ideas? Its used a little coolant but its the pesky
coolant elbows leaking. Or at least I hope that is where
the coolant is going. No bubbles in the radiator with
engine running. Intake gaskets?

used red MN · Feb 18, 2023

Hopefully your no bubbles in the radiator test was legitimate. As in the radiator was completely full and the engine was fairly well warmed up when doing this test. This would mean that if you replaced your intake manifold gaskets you would probably fix your problem. I believe those engines still have an upper and lower intake, this means you are replaced the lower gaskets that set against the cylinder heads. Do a web search for ..2006 Pontiac Grand Prix 3800 water in oil.. you will get a lot of info. I am linking one of the results that came up in my search. I have used their info before and it seems fairly legitimate.
Look at this
Editing to add: I overlooked the ..started using oil.. part of your post. The intake gaskets may or may not fix this issue. Did your oil actually change colors when you changed it? If so it may fix the oil use. Also if the oil changed color you are probably dangerously close to a rod bearing failure. Did you ever try to crack the drain plug after it has sat all night to see if water drips instead of oil?
Hope this edit does not screw up my margins and spacing, seems to be a common problem with the edit feature on an iPhone.

This post was edited by used red MN on 02/18/2023 at 12:38 pm.

wore out · Feb 18, 2023

GOOGLE ''2006 3800 plastic intake egr coolant leak''.

''The plastic intakes on these things are notorious for melting where the EGR passage goes through the upper intake. They ll melt there and there s a coolant passage to throttle body where it melts allowing coolant inside the intake.''

Stuart · Feb 18, 2023

It doesnt have a plastic intake manifold. I believe its
cast aluminum

Stuart · Feb 18, 2023

At 3500 miles on the oil change the oil was not milky. I do not believe there is water in the oil. The oil looked nasty because the crank case was not able to vent lol vapors

JF in MI · Feb 18, 2023

You say you changed the PCV but did you check to see if it is actually sucking air with the engine running? I've seen PCV hoses/tubes clogged.

Stuart · Feb 18, 2023

There are no hoses coming or going to the pcv valve it goes in a cast housing in the intake manifold. It sits in a twist lock assembly

used red MN · Feb 18, 2023

Thanks wore out! And this upper plenum could be an issue as well. See attached video, sorry the dude does not seem like ..Mr. Intelligent.. but he covers the problem. The thing about it is that coolant leaking there is more likely to get burnt in the engine than ending up in the oil. However, it still could if it ran in the intake and down an open valve into a cylinder and past the rings. I am guessing the amount of coolant getting in your oil is luckily minimal, but still enough to vapor off when the oil is hot and produce the yellow snot. The PCV valve being plugged could very well add to your oil consumption. I have driven 3.8 engine cars on my 4 day a week 35 mile one way commute 280 miles a week for 20 years; a few of them were the smaller cousin the 3.3.
Video of the upper plenum problem

This post was edited by used red MN on 02/18/2023 at 02:15 pm.

DoubleO7 · Feb 18, 2023

Stick your finger in whatever is sticking to the underside of the oil fill cap.
Then touch the substance to the tip of your tongue.
If it is antifreeze it will be sweet if it is the old school green/yellow stuff.
if it is oil and condensate it will have no taste.

This is not a joke, it won't kill you if you don't drink it.

My 1999 Tahoe with 350 had condensation under the cap and sure enough it was antifreeze. Oil never got murky/milky but the intake to head gasket was leaking.

NDIHC · Feb 18, 2023

I'd have to agree with those who said intake manifold. Not the aluminum lower intake but the plastic upper intake plenum that likes to burn the egr port which can lead to both exhaust gas and coolant contamination of the oil. If I remember correctly, most of the ones I worked on had unexplained coolant loss but I don't remember any having milky oil. I haven't worked on one for at least 18 years so my memory may not be perfect about that.

Kyle in KY · Feb 18, 2023

Agreed, the plastic intake plenum. Just replaced one for a neighbor, getting antifreeze in the oil. Its not a difficult job, more of a pain draining the oil and getting all the milky oil out.

Stuart · Feb 18, 2023

It does not have a plastic intake manifold

Papaw8 · Feb 18, 2023

Make sure the Pcv system is working properly. Not just the valve. Make sure engine is coming up to temp and not just short runs. Good thermostat?

Stuart · Feb 18, 2023

System comes up to 195 degrees. I put on 120 miles per day 5 days a week. 40 total on weekends

NDIHC · Feb 19, 2023

I see that they came with either plastic or aluminum plenum. The ones I usually dealt with had the plastic. I've been working in a non-GM dealership for about 18 years so I guess I'm not as up to date on these things as I thought I was! That'll teach me to rely on memory without confirming facts!

Sprint 6 · Feb 19, 2023

It needs LOWER intake gaskets, its pulling oil in from the valley because one or more intake port seal has failed. Make sure to use the updated version that are aluminum plates with rubber rings around the ports. Upper plenum on an '06 is aluminum, so only need a new gasket on it.

Stuart · Feb 19, 2023

I was not aware that they could come with either on.
So in your opinion is the manifold gasket the issue?

Stuart · Feb 19, 2023

Will it hurt the engine to drive it this way?

Stuart · Feb 19, 2023

Is fel pro a good gasket brand. Oreillys has one that looks like it is aluminum with rubber bonded to it.
I have gone away from oreillys for certain things like brake parts.

Sprint 6 · Feb 19, 2023

If the lower intake gaskets have failed, it will eventually get oil in the cooling system. Then the repair gets more costly.

The Felpro updated gaskets are alright, not my favorite, but are my second choice if I can't get gm. FYI, there is a coolant plate on the end of the lower intake that will need a new gasket while the intake is off. Be aware, the Felpro set DOES NOT come with that gasket, and it can be hard to find individually. The gm set DOES come with that gasket, and is usually cheaper than Felpro, to boot.

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