Oil in coolant...Buick 3.8

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Jul 13, 2008
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North of Amarillo
Greetings all, I have oil in my coolant. Don't know where its coming from, either the tranny cooler is leaking into the radiator or its coming from my engine. I will send a sample to Blackstone today if they check this type fluid sample. I flushed the cooling system yesterday and the color of the coolant is somewhat red...trans fluid in tranny is not milky but is a little brown and will flush it all asap. While waiting for results...what do any of you recommend? I guess I better keep in mind that the previous owner may have put some junk in the coolant for some reason, maybe to me it looks like oil...??? Should I pull the rad and have a radiator shop check it, or go buy a pressure test kit, pressure up my radiator or cooler and see if it leaks... Any suggestions will help. Thanks, Eric
 
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First things first ! You say there's ' oil ' in the coolant . Later you say the previous owner may have put something in the coolant . Did you just buy this car ? A pressure test seems to be a smart first move - if the previous owner suspected a leak and put in some sealer that may be what your seeing . Have a shop do the pressure test - hopefully you know of a reliable independant shop that can do the work .
 
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When my '01 Grand Prix with the 3.8 had oil in the coolant the UOA of the engine oil showed there was some coolant in the oil as well. Mine was from the lower intake gaskets leaking which most likely is your problem as well since nearly all these engines seem to do it eventually. If it turns out that is what the problem is, make sure you use the GM aluminum framed gaskets. I think they still sold the plastic ones when I had mine done a year ago. I don't know the best way to determine the exact source of the leak so I'll leave that to your mechanic or others to suggest. I'd check/change your oil immediately since coolant is NOT good for your engine when it is in the oil.
 

83126

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bruno...I bought the car several months ago and did not find this issue until recently. Will take rad to shop and pressure test Monday, thanks. WishIhadatruck...yes, I am aware of the manifold leak problem chronic on these engines. Thanks for the gasket info. I guess I should have the trans fluid and oil looked at as well. Thanks...
 
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could it be dex sludge?? For those unsure what dex sludge is we refer to the dex cool coolant sometimes as dex sludge because of the effects it has in the cooling system in some cars
 

83126

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Great suggestion crazyoildude. Sludge is a good description of what its like. What color is Dex?
 
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From a pure likely hood perspective, you have the dreaded GM DexCool and intake gasket problem. And you are right, prior owner may have known about it and popped in some sealer into the cooling system (and who knows what other system). Get the DexCool out ASAP. If you have the gasket problem, make sure they use a FelPro gasket and not a OEM GM gasket. While GM has redesigned their gasket, I think the FelPro one is even better from what I read. After the problem is resolved you could continue with DexCool or a DexCool clone or go to G-05 or Peak Global. I would go with G-05.
 
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 Originally Posted By: Donald
From a pure likely hood perspective, you have the dreaded GM DexCool and intake gasket problem. And you are right, prior owner may have known about it and popped in some sealer into the cooling system (and who knows what other system). Get the DexCool out ASAP. If you have the gasket problem, make sure they use a FelPro gasket and not a OEM GM gasket. While GM has redesigned their gasket, I think the FelPro one is even better from what I read. After the problem is resolved you could continue with DexCool or a DexCool clone or go to G-05 or Peak Global. I would go with G-05.
I believe for the 60deg V6 motors (3.1, 3.4, etc.) you want the FelPro gaskets but for the 3800 you want the aluminum framed GM gaskets.
 

83126

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Donald...I am hoping to find that the sludge in my coolant is dex. If my coolant and oil analysis come back clean, I still plan on doing both upper and lower manifold gaskets asap. At this time there is some oil seepage from the lower gasket, not enough to drip, just enough to make a mess. I figure I'll also do wires, plugs O2 sensor and whatever else to keep this thing running good for the next few years. So far its been a great car, quite boring as cars go, but comfortable and quiet. I will fill it with G-05 tomorrow.
 
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Are we really blaming dex cool? I had plenty of cars, and know plenty of cars with well over 100k and original dex cool, no sludge. Sorry, I do not believe for a second dex cool is a "gasket eater". Perhaps it sludges in some applications, but i bet ya anything the intake mani would leak in green coolant too.
 
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 Originally Posted By: VW_TDI_PD
Are we really blaming dex cool? I had plenty of cars, and know plenty of cars with well over 100k and original dex cool, no sludge. Sorry, I do not believe for a second dex cool is a "gasket eater". Perhaps it sludges in some applications, but i bet ya anything the intake mani would leak in green coolant too.
 
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