Update to post

I pressurized the air compressors coolant chamber to 15 psi. No air could be heard leaking from the chamber in to the crankcase.

 

What does antifreeze look like?

 

The antifreeze is clean. There is no backfeed of oil into the radiator.

 

Ant crack that would go between the coolant passages and the oil galley would put oil in the coolant.
The C12's water pump drains into the pan.
I would have checked that a long time before, I would have ripped the engine apart.
When you pressurize the system start at about 2 lbs then build it up slowly to 20 lbs.
Just a thought!

 

Thanks for the feedback so far.
We eliminated the water pump because it would leak into the front cover and enter the pan as coolant. I have seen a water pump leaking in this fashion. There is visible signs of the leaking. Also, the water pump is new. What we are seeing is oil being forced out of the oil galley as we pressurize the cooling system. I did pressurize the cooling system slowly, as I was using a hand pump system. The service manager said that as soon as I started pumping, the oil started flowing out of the main caps, and by the time I had built up to 10 lbs it was streaming out.
One thought the service manager had, was that when the engine is running, the block is hot and the crack is closed. When the engine is shut down, no more oil pressure, and the crack opens as the block cools. Residual pressure in the cooling system then forces coolant into the oil galley until the pressure reaches zero.

 

Should have held the pressure to it for awhile to see if it forced all the oil out and then streamed antifreese.

 

We know that it eventually streams antifreeze because of the build-up in the valve covers and breather filters. Did we really need to wait until it had crapped over a gallon of oil onto the shop floor? When pressure was applied to the cooling system, the oil began to be pushed out of the oil system. This we could see. The question is where is it happening?
This has basically become a moot point now, as my boss doesn't want to waste any more time with this guy. He has no money, and wants us to cover the repairs for him and he will pay the boss back by driving truck for us. I have been told to put the engine back together so he can get his truck out of our shop. I feel sorry for the guy. He got taken by the previous owners. He paid $10,000 for the truck, sunk another $20,000 in it getting it road ready (tires, etc), and paying taxes and such. Basically cleaned his savings out and he's got a pile of junk. Besides the engine issues he still needs to pass an annual DOT inspection, and I have already seen plenty of repairs it will need to meet standards. On top of that it's a rust bucket and will nickel and dime this guy to death if he attempts to go over the road.

 

I was involved with a 6L71 that would put oil in the coolant, we checked the cooler, the head gasket everything they thought of. We dyno'd it and never got it to leak, he would take it out and call at Leduc saying it was blowing oil out. I sat down with the GM district warranty representative. and a manual, we decided that we should check the head. I removed it, plugged off all the oil galleys, filled it with solvent, preasurized it and put it in the hot tank. When it got to about 170 F it lost preasure. We put in a new head core and destroyed the old one.
If the oil is flowing out of the maim bearings, I would ask did you remove the oil filter. I do not have a C12 manual but that may give you a hint as to which direction, the coolant is coming in,
Also I would blow out the oil galley and preasurize it then blow it out trying to locate the general area.
Just from experience, when you test an oil cooler fill it with solvent, if the coolant is going into the oil and not the other way around then you have to make an adapter to preasurize the cooling side.
I use to have a section of aluminum frame rail to make adapters. You may have to make adapters to plug off the block coolant openings for the oil cooler and see if it is the block.
You have to keep the antifreeze level up to at least -35F to find a leak plain water will not go thru wear antifreeze will, solvent will go thru easest, but not recommended in the block.
Just a thought!

 

Fascinating thread and mystery 'til your boss pulled the plug on further efforts. My sympathies to the owner.

 

I agree 100% it is the type of problem you have to really have a programed, plan of attack and a stop, even when it is a warranty situation, you can only go so far before it is time to re-evaluate and maybe go for a used engine.

 

Well, I just recieved an new direction. Do nothing more to this engine. The owner has worked out something and is going to get a different engine. Don't know what he's getting, but I think this will be the best path.
If the old engine is here as scrap I will definitely tear into it and see if I can come up with something to explain this mystery, and put a post up.
Thanks for all the help, and suggestions.

 

I have seen one cat do this and at cat school one time they told us of this problem.Cat said it happens some times but one liner had a pin hole thru it from elctrales and it was at the bottom of liner were one piston ring would stop over it when going down and as it would start up it would have a pumping effect of a small amount of oil thru the hole.Something like a piston pump ever time the ring would change direction of travel.The one I saw had not been overhauled but had antfreeze mixed causeing the coolant to work on the liners like I have never seen before.It took about six months to find.I don't remneber the model of the engine cause its been ten years back.

 

As the truck owner, or mechanic, not figuring out what was actually wrong would drive me bat**** crazy!

 

We had the same issues with the C12 we have.

Had 2 problems.

One, was the air compressor. It was also putting coolant in to the oil and air system. Has been nothing but a PITA since. All the coolant jacked up a lot of air valves on the truck and on the main trailer we pull with it. Took 3 different reman air compressors to get one that didn't leak. :bdh

2nd (and main) problem- The head on a C12 has small freeze plugs on the bottom side of it. Several were leaking coolant into the oil. Boss waited too long to deal with it, and wound up trashing the rods/mains, cam and followers,............. Ended up doing an in-frame. Should've replaced the oil pump, too, but they didn't. Told them to do it. :damnit :damnit

 

coolant is my oil and when I crank the truck oil is shooting through the little hole on the side of my oil filler tube ( where you pour your oil into the engine whats a possible fix

 

You need to first do a leak test.
The head is probably coming off, probably a gasket, possibly a porous liner.