My reservoir ran over while warming up. Got to looking and there is a good deal of oil in the resevoir and radiator, no water in the oil. Iam New to diesels but ihave had head gaskets go on gas fords in the past and it was obvious. The thing that gets me is that the truck runs great. Would you guys think that it is the oil cooler. Any input would be appreciated. The truck is 86 f250 4x4 6.9

 

sounds like the oil cooler failed. the oil cooler is that big tube thing on the left side of the engine block that the oil filter screws onto. its a heat exchanger between oil and water, and its not unheard of for its o-rings to fail and leak as yours is, or i've heard of them corroding through.
its a little challenging to get it off the engine, but it can be done.

obviously, you want to get it fixed before driving any more, and you'll want to change the oil and coolant when you're done.

 

That is what I was thinking but would it cause enough pressure to push water out of the reservoir? I been reading up on changing out the o rings on the oil cooler and I want to be fairly sure before I go diving in to that project.

 

Yup... Oil cooler has 15 to 45 psi oil pressure and the water is about 5to 16 depending on temp of the engine....get a o ring kit from typ4 he has the best o rings.

 

the ford dealer can get the o-rings too, but they'll charge you about a hundred bucks for them. most parts stores don't even have them listed.

 

Also, the black O-rings are garbage, typ4 had a fun experience with them only lasting ~20k miles and they cracked up and leaked, make sure you get the good ones (dark blue and green) so you only have to do it once. Also check when you have it out that the oil cooler tube isn't super rusty, them rust made pinhole are a pain when you just had it out 2 months earlier.

 

you can get the good o-rings for like $10 from rock auto and you can also get the cooler to engine block gaskets there as well. can do an oil cooler re-seal for under $20.

 

Thanx all of you for your input. I'm gonna tear in to it tomorrow. One last question is the oil cooler from a 7.3 the same as 6.9. Can they interchange?

 

yes, they can interchange. but one of the ends on the tube is different between pickups and vans, so if you have to replace it, you need to be aware of that

 

So I've got the oil cooler unbolted. The book doesn't say to pull any thing else off just the oil cooler itself and pull it out in one piece. Easier said than done. Is there a trick to getting it out with out pulling the exhaust manifold off?

 

i'm in a van body, so it may not be quite the same, but i was able to wiggle it out the back after i had the filter off of it. it is a little bit of a tight space up in there, i think you have to twist the whole thing one way or the other. play with it till it comes out

 

So I pulled the oil cooler out and the o rings were hard but not cracked. So I then did the best pressure test I could on the cooler and as far as I could tell there was no leak. I put a piece of water hose in one side of the oil passage and put my thumb over the otherside submerged it in water and pressurized it with a air compressor. It would blow bubbles out around my thumb but none through the water baffles. Do you think that was sufficient? And any other ideas? I heard there is copper gaskets around the injectors that could be the cause? Any suggestions would be great but try to stray away from head gasket if you could lol.

 

you may as well replace the o-rings anyway. theres also a chance that one of the gaskets where the oil cooler mounts to the engine may have been leaking between its ports, i don't know if you inspected them while taking them apart, but i would suggest you go ahead and reseal that oil cooler, then take it for a test drive and check your fluids again.

 

You Might want to remove the drivers side engine mount and jack up the engine. This will give you more room to work.

 

Would it be wise to apply rvt to the manifold to block gaskets?