Coolant in oil after Head Gaskets replacement

[Matt Brandsema]

Hello all,

I am working on a 1999 Pontiac Grand Prix GTP Supercharged 3.8L. Turns out both the cylinder heads were cracked. I went on a wild goose chase trying to find two heads that weren’t cracked, then had the machine shop do a full valve job, and resurfacing.

When I fired it up, it sounded great! I shut it off, waited only 5 minutes or so, and then started it again. Long cranking times, which had me suspicious of an internal coolant leak again. Shut it off and checked the oil. Sure enough, coolant/oil mixture on the oil dip-stick. This must be a pretty large leak!

I really don’t know what could have happened, I followed the factory service manual to the letter. Torqued the head bolts (after replacing them since they are TTY bolts) in sequence to 37 foot pounds, then an additional 120 degrees with a torque angle meter. My ideas..

1.) Many of the head bolts go into coolant passages. I didn’t use any sealer on the bolts. This is because the service manual didn’t say anything about using sealer, and the bolts looked like they had some kind of compound on the threads, so I didn’t use a sealer. Could this be it?

2.) Maybe the intake manifold gasket(s) shifted during install, causing an internal leak. (I doubt it though!) I didn’t torque the intake manifold bolts to spec.

I am going to do some tests in a few days to try and nail down where the coolant is coming from. I am concerned about hydrolocking, so my first thing is to remove all the plugs (or injectors) and see if (where) coolant comes out.

Topic

[Glenn]

Hi Xylus,

I hope this doesn’t insult your intelligence…you’ve done a lot of work, and it sounds like you have been careful about it. Before going any further, I would suggest changing the oil and filter again. Let the engine run until normal operating temperature is reached, then change the oil after that. After doing an extensive job on my engine as a result of coolant in the oil, I was surprised how much coolant was still present. This can accumulate in the bottom of the oil pan too, after a significant leak. Here is a picture of the inside of my oil pan during the job.

At first I thought either the head gaskets or the intake manifold gaskets were still leaking. After changing it the second time there was no more coolant present.

A second suggestion would be a compression test on each cylinder. It sounds like you intend to take the plugs out anyway to check for coolant in combustion chambers. This might be a first step to ruling out head gaskets failure if compression is good…just a couple quick things I might do first if faced with your challenge. Best of luck to you…

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[Eric]

I’m sorry I don’t have an answer to your question but I do have a question to ask you. I’m about to replace my upper and lower intake manifold gaskets and wanted to ask you a question. About how much time do you think it would take to tear down to the lower intake manifold gaskets? I have never been this far down in my engine before. I have only had the upper intake off. I have a 2000 Grand Prix non super charged. Thank you. I hope you get your coolant leak figured out. And I have read before, like tomatofarmer1 said, that there can be a lot left over in the engine in passageways and in the oil pan. I don’t know if you dropped the oil pan or not but I think it’s a requirement if there’s coolant in your oil.

[Matt Brandsema]

Thanks guys, I will keep you updated.

[quote=”ewhitaker0020″ post=94956]I’m about to replace my upper and lower intake manifold gaskets and wanted to ask you a question. About how much time do you think it would take to tear down to the lower intake manifold gaskets?[/quote]

I would definitely set aside a few hours. Especially if you have never done it before.

[John Hugon]

Xyius,
It’s really hard to get all the coolant out after coolant enters the crankcase…as tomatofarmer1 illustrated

ewhitaker0020,
On a non super charged 3800 check the intake Plenum first. When I worked on them during the warranty coverage period, this was a big problem. we did not have very many head gasket problems, but I heard after that engine got out of warranty it did….because of Dexcool…hope this helps

This is what happens in a write up from independent shops…

GM used the 3800 V6 Series II in their full sized cars from 1995-on. The engine can be distinguished by a large plastic cover that says Series II on it on top of the motor. It was first used in 1995 Pontiac Bonneville, 1995 Buick Park Avenue, and 1996 Olds 88/98, Buick LeSabre models. From 1995-1999 this motor has a tendency to develop coolant in the oil. Many people assume a blown head gasket or a cracked head or block. However this is not usually the case. GM made the upper half of the intake manifold out of plastic on these cars. Early models had a tendency to warp and deteriorate the plastic where the EGR tube admits hot gas into the engine to re-burn for emissions control, and this causes a leak to develop where engine coolant goes in and out of the manifold around the throttle body. A coolant leak from the hole eroded in the plastic, and runs down into the lifter valley, or is sucked into the engine and burned. In extreme cases the cylinders will fill up with coolant and hydro-lock the motor. Usually this is seen as a symptom, by white sludge that looks like soft-serve ice cream built up in the top of the oil cap or in the PCV system, and the engine is going through a lot of coolant, and you can smell hot coolant especially in the exhaust. The fix for this is to replace the upper intake manifold with an improved design that is on the market. It is available at most parts stores or through the dealership. Cost of the parts is about $150 plus it is advised to flush the oil system and change the oil, and replace the spark plugs if they are fouled out due to the coolant in the cylinders. Total labor is about two hours. Compare this to the cost of new head gaskets, which often are not the problem and you, can see why so many people often sell or junk their Series II 3800 cars cheaply. If you know what you are doing this can be fixed easily. In some cases there may really be a bad head gasket, but since the upper intake must be removed to service the head gasket, it is easy to inspect before you go any deeper into the engine.

[Bill]

I would pressure test the cooling system to see if it holds pressure. If it does or does not I suggest to drain the oil and watch for coolant draining out of the oil pan while it’s pressurized. If it holds pressure and no coolant drips out I don’t see a problem. Simply change the oil filter, fill with oil and carry on.

If coolant drips with the drain plug removed I would say that the intake gaskets or head gaskets are wrong or have slipped out of place. There is a possibility that there is a fault in the intake manifold such as corrosion or a crack also.

[Matt Brandsema]

Hey guys! I changed the oil again and everything is good!! There must have just been some left over coolant as you guys said. Thanks!

[zero]

You could have also used some used oil the first change and used that to flush out the coolant. Who doesn’t have a jug of used oil kicking around.

[EricTheCarGuy]

As some have pointed out, it does take a while to get all the old oil out of there. I’m glad that was the only issue. That’s a lot of work and it would suck to have a problem after all of that. Glad you got it sorted. Thanks for keeping us updated.

[Author]

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