Oil in rad?!?!?!

[heheheha]

Hey
Friend has a 93 Buick Le Saber GS, usual GM 3.8L in it. He has found trace amounts of oil in his rad. So we drain the oil but the oil has no coolant. Head gaskets appear to be ok. I myself don't think that oil would leak into the rad (cooling system runs at a much higher pressure, so a leak somewhere would put the coolant into the low pressure area, the oiled area), but I could be wrong.


So what the christ is wrong ?

[fiero308]

Are you sure it is engine oil and not trans fluid?  Thinking about the trans cooler in the rad, here. 
Assuming that it is not;
 I think the cooling system probably has a lower pressure than the oil system.  Although they vary all over the map, oil pumps tend to put out somewhere around 40 to 50 psi; varies with the engine and the length and complexity of the oil passageways; and a cooling system normally operates at something like 15 to maybe 18 psi.  The thing I am not sure about is where the two would be physically 'close' enough so that one could 'bleed' into the other.  Ie the oil passageways tend to be more internal and the cooling passageways tend to be largely focussed on the head(s) and upper end of the block altho there is a water jacket around each cylinder as well.  There is comparatively less oil under pressure in the cylinder head area but it DOES go there to lube the rockers and lifters etc.
When head gaskets blow (or leak) it usually seems to be coolant going into cylinders, simply because of the number and size of coolant passageways around the top of each cylinder.  That usually results in a pretty noticeable loss of power and often white (or other) smoke out the 'pipe.  They would know pretty soon that something is wrong.
So there are a few thoughts, anyway - no solution, but at least you may assume that it COULD be oil (and check the trans situation too)
Make sure you post what is found out.

[heheheha]

He stopped by for a few minutes today and I got to take a brief look. A small leak at the front head, but nothing big. Checked out the res. and it was...not green It doesn't look like oil really...maybe dirt or tranny fluid as you suggest. Never evn thought of the trans lines...the oil itself is fine...

Monday looks like it will be a more thorough look day...Will let you know what I learn then.

*edit*
Oh, and while the fluid in the res was a greyish color, the stuff in the rad was pretty much fine, with only a VERY slight amount of dirt/oil/whatever.

[heheheha]

OK. Got to take a more thorough look. Flushed out the coolant so we could start out fresh and clean. After 3 days it's still and clean, so I guess it was just dirt.

[Sentinel]

You'd be surprised how stuff gets in there, last summer I noticed a leaf in the overflow resivior, thought it was rather strange, so I attempted to fish it out, turned out to be a mouse, no idea how the bugger made it in there.