My son was visiting this week so I let him drive my 2000 4x4 N/A truck.

He called to tell me it overheated and there was what looked like oil in the radiator overflow tank.

When I got there at lunch time to check on it I saw that the oil filler cap looked fine and the dipstick did too.

The overflow tank looked a bit muddy like something was mixed with the water.

The tranny dipstick looked a bit low on fluid so I am wondering if maybe the oil cooler lines have mixed somehow with the water in the radiator?

I had to drop him back home and I'll have to check it out after work tonight.

Hope it's not a head gasket and equally hope it's not the tranny but just the cooler lines or something not too expensive to fix!