oil in coolant overflow tank?

[mmltml]

I'm at a loss.

How is oil getting into my coolant tank? When I check my oil, it looks good and clean; no "milky" looks and when I take the radiator cap off the coolant looks nice and green, but in the overflow tank, there is clearly oil in there.

My car has the infamous o-ring oil leak. Im pretty sure that the head gaskets are still good because i don't see any leakage around the heads, or anywhere around the engine.

Oh, my car is a 95 Monte Carlo Z34. 3.4 DOHC...any thoughts??

[OldSkoolGP]

Do you have an oil cooler? I have never seen it, but that would be the easiest way for it to happen. It if cracked internally somehow, I'm sure there's enough oil pressure to force oil into the coolant passages of the cooler. If you don't have a cooler, the only other place oil and coolant are in the same proximity is the heads. I hope it's your cooler.

[robertisaar]

i saw this issue a long time ago(1997 or something), and my dad ran block sealer through the cooling system... no problems since. i'm talking about a 95 3100, but same idea.

[IsaacHayes]

Is it transfluid? Mine did that when the internal cooler busted in the radiator. New radiator was the fix. See if the oil is reddish on a paper towel....

[mmltml]

it is clearly oil, not trans fluid...its definitely BLACK in the overflow tank. and my dipstick oil is clean and dark brown, like it should be.

I actually wouldn't be too upset if it was the head gaskets because it has the infamous oil leak (o-ring seal) where you have to pull the heads anyways, and i've been planning on fixing that eventually.

[GTP091]

You don't need to pull the head to fix the o-ring leak just the plenum. Unless you want to do-it by the book.

[55trucker]

Try flushing out the recovery tank, and keep an eye on the entire situation and see if you get more oil in there. How long have you owned the car?

[mmltml]

well i took it to the mechanic for another unrelated problem and he said that the gaskets were in fact blown so now i know how its gettin in there

i've owned the car for about 9 months now...it just turned over 96k miles

[55trucker]

EEK.....can't win for losing.

[3400-95-Modified]

well i took it to the mechanic for another unrelated problem and he said that the gaskets were in fact blown so now i know how its gettin in there

i've owned the car for about 9 months now...it just turned over 96k miles

Yeah, blown head gaskets will not always result in coolant getting into the oil. Sometimes it will just get fuel and carbon and other oil blow by from the cylinders into the coolant.

[savannaz34]

You don't need to pull the head to fix the o-ring leak just the plenum. Unless you want to do-it by the book.

i totally agree with you,ive done it on both of mine.
but i regret doing the one on my 92.i know my 91 had the top end done a few years back,but im not sure about the 92,therefor i wish i would have just tore the top end apart and fixed it properly,and find out what else is going on in there(if anything)but more than likley there is something on its way out.
but any ways, i now disagree with changing the o-ring the easy way.

[savannaz34]

well i took it to the mechanic for another unrelated problem and he said that the gaskets were in fact blown so now i know how its gettin in there

i've owned the car for about 9 months now...it just turned over 96k miles

have you tried to pessure test the coolant system,its usually the best and easiest way to find a coolant leak

[mmltml]

yeah i think i'm gonna do it "by-the book". well im not going to do much except pay for the bill lol because i don't trust myself enough to rip apart my engine and expect it to be right lol...and ive known the mechanic for all my life and we take all of our cars there and i know he'll do a good job.

i would pressure test my cooling system...if it was leaking coolant...haha

[savannaz34]

if you dont have a leak any where than how are you getting oil in the tank?

[mmltml]

i figured it was the blown head gaskets