View Full Version : oil in radiator

06-19-2007, 01:01 AM
I have a "90" F-250 7.3L Diesel 4x4 that just started showing oil in the radiator. I'm afraid to ask but, what does this mean? What's failing? I've never seen this in a gas motor before.
And at less than a hundred grand on a diesel I would like to think a major overhaul would not be needed. I can hope right :) Oly

06-19-2007, 01:45 AM
If it has an auto tranny with the fluid cooler integrated in the radiator then it could be leaking. You can plug one end of the cooler then apply compressed air to the other connection. Then look for bubbles in the radiator. If it doesn't have a cooler in the radiator then I would guess it's head gaskets.

06-19-2007, 08:43 PM
The 7.3 has an engine oil cooler. I would suspect that first.

06-20-2007, 12:49 AM
if it's not the oil cooler, than it could be a blown headgasket, cracked head, or cracked block.

06-20-2007, 06:32 AM
Is there water in the engine oil? the oil would look frothy. (head gasket)
Is there water in the trans fluid? (trans cooler)
Do you have white smoke (steam) coming out of the exhaust? (head gasket)
If you run the motor with the radiator cap off, do you see bubbles? (an occasional bubble is normal) (head gasket)

I'm leaning toward trans cooler also.

06-21-2007, 10:28 PM
It can depend upon what type of oil that you are talking about as to which cooler is defective.

If you have oil, be it transmission or engine, in your coolant, then you have a bad cooler in your radiator. Since the oil pump is operating at a greater pressure than your cooling system, the oil is able to leak into the cooling system. (A cooling system with a bad transmission cooler will turn the coolant into a pinkish mix. That is why transmission fluid has the red dye in it. On the other hand, a bad engine cooler will have the coolant and engine oil trying to separate from the water with a grayish appearance.)