I am trying to track down a coolant in oil issue on a 2002 DII with 131K miles that my son recently purchased. We purchased assuming it had a bad head gasket (coolant in oil). When we got it towed home the compression tested 155-160. Pulled the oil pan and pressurized the cooling system at 18 psi and it held over night. Replaced the oil pan, oil, filled and bled the cooling system, and drove a few miles. Everything seemed fine. There was still a little water in the new oil, but I was not sure how much was trapped in the block.

Next I decided to run a combustion gas test on the cooling system. The fluid turned somewhat green (positive but not yellow). I did the test in my garage and was concerned exhaust may blow back into the garage and skewed the test. I took it back out to get it up to temp to run another test outside. I drove about 8 miles and it overheated. I pulled the dipstick and it had about an extra quart of water in the oil and decided I better not drive it further and it must be the head gaskets.

I pulled everything apart and found that the gaskets had already been replaced (looks recent) and appeared in good shape. It appears that no machining had been done to the heads, but I did not see any obvious damage or warping. I found several loose bolts, missing clamps, the upper intake was clearly not torqued to spec, etc. on my tear down which leads me to wonder if the previous work was defective or if I have another issue. The head bolts did seem to be reasonably tight. Even if previous head gasket were not 100% correct (warped head, etc.), I am not sure how it could get a quart of water in the oil in a few minutes. With a decent compression test, i would not think significant coolant got past the rings to the oil.

Finally, to the original question. What are the ways that significant coolant can get into the oil in a short time frame? I am trying to find a way to pressure test my block. I am aware of the timing gasket, but I assume a gasket would not hold at 18 psi, but fail only when it got hot. I will probably pull this next and at least look at it. Is there an oil cooler in the radiator that could mix oil and coolant? I saw evidence of a small leak in the water port of the lower intake, it didn't seem large and did not appear that it got under the valley gasket to get into the oil.

It seems that the most logical conclusion is that the block is cracked an leaking directly into the sump, but that would not explain the combustion gasses unless my test was contaminated. It does not seem likely that a sleve would leak into the sump and cylinder at the same time. I am going to find a way to pressure test the block, but i thought I would see if anyone had any other suggestions of things to check. I have done plenty of research, but I can not come up with an explanation that makes sense to me and I do not want to try to randomly fix possible problems. Thank you for taking the time to read and any ideas you may have.

 

Could be a crack in the block behind a sleeve or somewhere in the coolant passages. These motors are notorious for being excessively porous as a result of the casting process and they develop micro fissures in the casting which can ultimately lead to major cracks. Overheating is incredibly bad for them. If the head gaskets look new and there is no sign of leakage from there, best bet is that you have a cracked block somewhere...

 

Thanks, I guess pressure testing the block will confirm if that is the problem. I am hoping for another answer, but am afraid that you may be correct.

 

Timing case a gasket leak?--jacket to timing case interior???
A common area of coolant ingress "companeros"
T/V

 

You can always find another engine for these. It really comes down to who you can meet online that parts these out. I see people part out older DI's and RRC's and sell the motor and transmission for $300. Check the AZ LR Facebook page.

 

I am planning on using block off plates and pressurize the block's water jackets to 40 psi. I will try to plug the outlet of the water pump and remove the oil pan. I hope any leak (including remaining gaskets) would be obvious since that is more than 3 times normal operating pressure. I think 40-45 psi may be the pressure generally used to test the heads' internal jackets. If I am successful, I'll report back.

 

Thank you for the suggestion. I will look into it. I can not justify one of those $5-6K engines for a truck worth $4K ? fixed.

 

Oil cooler is divorced from the radiator.

That much coolant in the oil in a short time frame, will almost always point to cracked block. A fissure behind the sleeve will very often result in coolant in the cylinder and even more in the oil pan. This is from personal experience recently.
Not to rain on your parade, but the PO probably found this out after a gasket replacement didn't fix the problem. A "For Sale" sign was their next purchase.

 

That would have to be a pretty significant crack. Subscribing to see what your pressure test reveals.

 

Are you all suggesting that not machining the heads when the HG's were replaced could not lead to this?