Oil in Cooling system

Hi Guys,

My son just purchased a 1990 Sierra 4x4 with a 5.7 a few weeks ago and noticed
he has added about a quart and a half of oil since the time he's had it (about 1500 miles). The truck runs good and shifts good.
It doesnt smoke or leak oil anywhere, but I noticed that his coolant
overflow bottle and radiator have green/brownish color to the fluid.
And it feels oily. I suspect the oil cooler in the radiator has a leak,
causing the problem. There is no trace of coolant in the crankcase or in the tranny. Is this a problem with these trucks?

Let me know what you think, Thanks!

Rick

I am the original owner of my 90 GMC K1500 with 109K miles on her. I have not had this problem.

It does sound like the oil cooler is leaking in the radiator. Since the oil pressure is higher, you will have oil in the coolant but not have coolant in the oil.

//2000CAYukon

Thanks! I suspected it probably is the radiator, I'm going to replace it and see if that does the trick.

Thanks again!

Have the radiator pressure tested before you replace it. Take it to a radiator shop and if they find a problem, they should be able to fix it as well. You may not want to do this, but it is another option. Having it checked first will at least tell you if it is the problem.

Ok, I replaced the radiator and it seems to have taken care of the problem. Thanks for your help!