1983 CUCV M1008 Oil in Coolant

[Justang]

Hey guys,

I was doing a cooling system flush on my fully original 1983 CUCV M1008, when I came across something upsetting- my new radiator and coolant reservoir were both full of motor oil. I drained the oil from the motor and it was clean.

After new oil and hours of cleaning the radiator, reservoir and a full engine block flush, I drove it for another 30 minutes and by the time I got it back home there was so much oil in the radiator and coolant reservoir it had actually overflowed out of the reservoir onto the ground. After checking the oil dipstick, the oil was again clean.

This truck only has about 81k on it and I have never driven it hard or let it overheat. Always maintained regular oil changes, tune ups, and pretty meticulous care overall since I have had it. My guess is a blown head gasket, but I don't understand how oil could get in the coolant but no coolant is in the oil.

Any other ideas? Thanks!

 

[Justang]

By the way, the engine still runs perfectly even with the oil in the coolant- no rough starts, rough idles, or anything out of the normal.

 

[12vctd]

depending on how the headgasket let go, or the head cracked the compression from the motor could be pushing the oil into the coolant passages, but your H?G might be fine. also the oil cooler could have a leak in it which this is a new radiator but I have seen where the tank has a small hole in it, but usually with this problem theres a mix on both sides as when the truck is shut down the oil pressure drops to 0 but the cooling system still has pressure. Also check your trans fluid levels even when red trans fluid mixes with coolant makes same cream colored gunk. I would def pressure test the cooling system and see if it holds pressure.

 

[Justang]

Aack didn't think about a cracked head. I guess I'll just have to tear her down and see what's what inside.

 

[12vctd]

well again it might be the oil cooler. I would pull both lines to radiator and using very little airpressure I would plug one port with your finger and put some air to it, see if it pressurizes or just leaks into rad. Then you can get a coolant pressure tester pull the oil pan and pressurize the coolant system, while looking from underneath, this should allow you to see a leak if theres a crack or blown hg coolant will start to trickle down the affected area cylinder wall.

 

[Justang]

The tranny oil cooler runs through the radiator. However the motor oil cooler is a separate "s" tube mounted in front of the radiator, so I'm not quite sure how oil would get into the coolant from there.

 

[12vctd]

That was a brain fart from me, later 6.2's had a cooler that ran into a tank in the radiator just like a tranny cooler.

 

[acmunro]

Don't feel bad 12vctd I have (3) 1982 1/2 and 3/4 ton 4X4's with the 6.2 diesel and they have the engine oil cooler in the radiator.

 

[blzrgb]

I've had the same thing happen to a civy 6.2 a few years back. It was the head gasket around #8 cylinder. Be sure to have youre heads re-surfaced and check the valves before you put em' back on.

 

[12vctd]

well I have only seen them in the radiator, but then again I never payed much attention to my cucv's because I swapped the 6.2's out. I just have to stop posting after working 18 hours a day lol, no matter what it is I hope its a simple diagnostic and reapair.