07 Int 4300 Durastar coolant coming out of crankcase breather?

Good morning all, thanks for reading. I don't typically operate on diesel engines, but as maintenance manager I have been doing more and more of it. I am hoping someone can help me understand what is going on with my truck. Here is what I know:

2007 International
Durastar
4300 series
DT466 engine (not Cummins)

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So, about 3 months ago the truck pulled into the plant as the temp warning light came on. Driver said temp gauge was just a little past normal. Checked coolant and it was maybe 3-4 gallons low.

Topped off coolant. Warmed up truck for an hour or so, looked for leaks. Exhaust seemed dry, not humid. Looked for water in oil and oil in water. Could find no evidence of either. Visually looked for leaks, could find none.

Tested thermostat and it was barely opening. Bought a new thermostat and heated water over the stove, new one opened normally while old one did not. Installed new thermostat.

About 2 months ago, still losing coolant slowly. Still able to take 4 hour trips without overheating. Removed and inspected water pump. Water pump seal was corroded and questionable. Replaced water pump as I thought coolant may be bypassing water pump seal. Still losing coolant at a rate of 1 quart every 30 minutes.

About 6 weeks ago, lost 2 gallons of coolant in a 100 mile trip(mostly freeway).

Yesterday: Have not driven it since the 100 mile trip. Had to charge the battery to move it because driver left it on accessory. Driver managed to get it running before I arrived and let it idle for an hour or so to build up some charge. I arrived and noticed steam coming out of the crankcase breather.

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There you have it, steam coming out of the crankcase breather, so coolant in the crankcase. So now I'm thinking blown head gasket. I drain some oil out of the drain pan, and no evidence of water. I checked the oil dipstick and there was a spot of that buttery substance(oil and water mixed). Not at the tip of the stick, just some slurry in the middle. I could also see water droplets all up and down the stick.

Northwest Diesel told me that the oil cooler was not the issue(as my research online indicated), he assured me it was more than likely the cylinder number 4 sleeve, and quoted me $12,500 to repair.

So I called a few other shops. Most of them did not want to touch the DT466 engine. Then I called Erker Truck and the guy was super forthcoming and very knowledgeable. He said that, "with that truck, if the #4 cylinder sleeve needs replacing, then it's going in the basement." But then he told me that from what I said it sounds like it's not going into the basement. He said that if the oil cooler is leaking it will drink that coolant right up. He said as long as there is no evidence of water in the oil pan then it's probably a leaking oil cooler.

I gave the same information to NW Diesel as I did to Erker trucking. NW insisted that a leaking oil cooler can only introduce oil into the water, not vice versa. He insisted it was a problem with the head or one of the cylinders. Erker, on the other hand, said if the cylinder sleeves needed replaced, we should consider getting another rig instead of repairing it. He also said that he doesn't think that would be necessary because coolant is staying at the top, and not mixing with the oil in the pan. He thinks it's the cooler.

Can anyone confirm or deny either of these shop's preliminary diagnosis? Please forgive me for not being the most knowledgeable diesel mechanic. Any gas engine I would have purring like a kitten, but this is a different beast.

Thanks for reading!

 

Thank you Star Rider. I am dropping the truck off Friday at a well reputed shop and leaving it with them over the weekend. I will post the results. Was that front cover seal hard to replace? From what I understand there is a seal for the oil cooler that can fail and cause the engine to drink coolant and spit it out the crankcase breather.