I am going to be repairing a 1994 GMC 2500 3/4 ton with a 454 7.4 V8. The symptoms I am getting are what appears to be oil in the coolant, but there appears to be no coolant in the oil. No sweet smelling exhaust, or coolant loss. So I really don't think it is a head gasket problem.
Has anyone else had a problem similar to this? Any help would me much apprecated as always.

-dannyh

I am going to be repairing a 1994 GMC 2500 3/4 ton with a 454 7.4 V8. The symptoms I am getting are what appears to be oil in the coolant, but there appears to be no coolant in the oil. No sweet smelling exhaust, or coolant loss. So I really don't think it is a head gasket problem.
Has anyone else had a problem similar to this? Any help would me much apprecated as always.

-dannyh


Engine oil cooler has a leak?

If it had a leak, at what spot would it leak into the coolant? It might be transmission fluid. I can't really tell. When it mixes it is hard to tell what kind of oil it is except dark. Where does the transmission cool its fluid at? Could it posibbly leak from the cooler into an engine coolant line? Just a thought.

I think there is a tank in the radiator that cools the oil just like the transmission so maybe its leaking from in there.

My 90 GMC K1500 5.7 has both an engine oil cooler and tranny oil cooler in the radiator.

I also think that one of the coolers is leaking into the radiator.

//2000CAYukon

The way the trans cooler works.
There are trans lines that go to the rad, "only trans lines", inside the rad tank there these lines run the length of the tank back and forth a few times, it works on the basis of heat transfer, exactly like a boiler system.
These lines not only cool your trans fluid but heat it as well, trans fluid has an optimal heat range, too hot no good, too cold no good.
Many GMC trucks have factory trans coolers that go in front of the rad as well, mine does, also oil coolers.
You can rule out the rad trans cooler in the trans before you go opening up the engine by simply disconnecting the two trans lines that go into the trans and connecting them together by means of a hose or mechanical fittings and tubing, this eliminates the rad trans cooler, but I would not run it like this permanantly, the trans needs a cooler.
One thing I have heard many times is that 454's are pretty good at cracking heads.
It is very strange not to have fluids exchanging back and forth and only transfreing one way if there is a small crack between the two systems.
You never mentioned if you checked the tranny fluid for coolant.
If you just run pure water in the rad it might be easier to see exactly what is getting into your cooling system, the difference between trans fluid and oil are pretty easy to tell, look, smell, and feel are very different.
If there are oil coolers that run through the rad as one poster stated it's news to me, on GM products that is, especialy in the year model you posted.
Mine is a 91, and all the bone yards I have gone through looking for parts for mine I have yet to find a rad like that setup with a trans/oil cooler.
Wish you luck in finding the source of your problem.