Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Oil in my Radiator

I have a 1989 manual drive TOYOTA 4RUNNER, diesel.

My mechanic has done everything, new head gasket, machined the head for warp, pressure tested the engine block, and the engine oil is still leaking into the radiator. My car used to have Air-condition but since it hasn’t worked for over 5 years the compressor was removed, could this have caused the oil to leak after all those years. I am desperate for an answer… every body’s help is appreciated.


Bad news. Assuming the mechanic did the head gasket job correctly and the head is in good shape, it sounds like the engine block may be cracked. Is this a V-6 with two head gaskets or an inline 6 with one?

Air conditioning system is unrelated.

mate thanks for the comment, no the vehicle is not a V6 it is a four glow plug engine with just one gasket. I had driven the vehicle for a while and the engine seems to have a powerful thrust, if the engine block was cracked how would I know??? is there anyway to tell that the engine block was cracked. Just a note; you know were the oil filter is fitted, well that whole unit the mechanic suspects is worn, it looks like an oil cooler system, it has two rubber O-rings and a gasket, where the O-ring goes the groves are worn, a gasket & O-rings were fitted but the oil still leaks from/in this area.

This can be tricky…when you first had the head gasket done I am assuming it was because of either your oil was milky or visa versa…now after you changed everything and properly fixed the head…Did you ever pull the radiator and run degreaser thru it? Oil is a ROYAL BITCH to get out of a radiator…perhaps you have residual oil contamination in the rad that was never removed after the first failure. That is more likely than a failed repair attempt I think… Unless you wrecked your engine block…then it can mix it up at that point… Your radiator can also have a cracked trans cooling line…if that line fails then you will get oil intermixing in the rad as well. Is your engine oil milky too? If your hoses and rad were not properly flushed out with hot water and a mild degreaser I would have done that.

What was your inital failure?

ok, your right the head gasket was done because my mechanic thought that was the fault, there is no milky oil or water mixing with oil in the engine, a thick milky oil only in the radiator and yes the radiator was flushed with degreaser and cleaned.

Where can I find the radiator trans cooling line??? mate your help is very much appreciated especially here in Papua New Guinea (were just above Australia)

Only SOME rads have the trans cooler integrated into the bottom portion of the rad. IF you have one…and I dont think you do unless you have an auto trans…and I doubt that. Sometimes they will install only one style of radiator…(like todays aftermarket) and this would be the auto trans style rad…you can use this style in an auto obviously but also in a manual…as it wont harm anything to not use the cooler lines if you dont have the auto…I have run my engine oil into one of these radiators one time just to rig up an oil cooler of sorts…not a great idea and didnt do much cooling but it was there and I wanted to say I did it…I was 18 at the time…so I was goofing around.

Now on your truck…I really doubt you have an auto…am I wrong in this assumption? If I am not then your trans lines will enter the rad near the bottom or on one side or the other…you will see a bung on the rad…hard to miss…but if this ever sprung a leak internally it would surely puke the oil into the coolant.

yes your right, my 4X4 4runner is manual drive, can the engine block have a crack, what happens to the engine would I have power, full power, if the engine block has a crack?

You engine block or head may have a crack that cannot be seen with the naked eye. The mechanic needs to have it magnafluxed when its apart to find the issue