I have a 2000 3.9L that i have had for about a year now, and it just hit 100,000 miles, so I was doing a full tune up on it today,plugs, wires, cap, oils and fluids, and i checked the coolant dipstick and it seems like theres oil in it. I ended up taking the upper radiator hose cap off and the coolant is a perfect green, no trace of any oil. I don't know if the oil could just be some type of corrosion and it just needs a flush or if the oil cooler or transmission cooler is leaking into the radiator..Im stumped..any info would be helpful, thanks.

 

Welcome to the forum Josh.

How's the transmission fluid look? The oil? While with the engine running the oils would be forced into the coolant when you shut it down, it goes the other way.

IF you have a problem. Try a pressure test. You could also flush it and see if it happens again.

 

Last time I had that I had a blown head gasket. Does the overflow tank smell like exhaust? I could occasionally see mine bubble.

 

When I had a leaky radiator I used a radiator leak fix (Barstop?) and it left a brown oily looking residue in the coolant tank.

I hope it isn't a blown head gasket, as that is what you will see with one.