Okay, after an incredible amount of frustration in finding parts for a nearly 30 year old Case 550G, I replaced the oil cooler and gaskets, and I think that fixed the issue with oil in the coolant. When I changed the oil, I found that there was some water in the oil pan, (oil discolored slightly, but no visible water drips when I took the plug out). After changing it, and running about 30 minutes, the new oil is still clear, and after three flushes (two with dishwashing detergent, one with Simple Green), I got most (most) of the oil out of the cooling system. Since I know the oil pressure was higher than the water pressure, I felt pretty sure the oil cooler problem is how the oil got into the coolant, and since the housing was cracked very visibly, (and the gasket torn up), I know it's logical that some water drained into the oil. That much, I feel comfortable with. So now what? I'm guessing I should change the radiator hoses, since oil isn't good for them (good luck to me on getting hoses, the Case place took three weeks to get an oil cooler gasket). I am running straight water in the radiator to keep flushing things out for a couple of more days before putting coolant back in, and I'm checking the oil several times a day for signs of water getting back in there. (I'm still worried about a crack in the block, or at least that I had to buy a "used part" for the oil cooler, which was un-tested, of course). Does anyone have a magic formula for getting oil out of the cooling system other than "drain, run, fill, repeat"?
Sounds like you are on track. Just watch your hoses for awhile. Or, pull an easy to access hose and look inside. If the epdm material isn’t soft and gooey, they are probably good. For cleaning, automatic dish washer detergent is popular because it doesn’t foam up like liquid dish detergent does. Caterpillar, for years, has recommended Cascade. The good stuff in dish detergent has been banned. The Obama Admin EPA did that. Sodium Tripolyphosphate (TSP). Here is the trick, you can still purchase Cascade Professional Fryer Boil Out. It’s supposed to be the same Cascade formula you could purchase at the grocery store. That’s what I use. My magic formula. 1/2 cup for a 15 liter engine. Your mileage may vary.
I would not sweat those hoses unless they appear bad. At 30 years they probably don't look all that hot though. LOL @Coaldust beat me to it.
Should be a Cummins engine even though Case calls them by a different model
Well, I I wasn't 100% sure, since it absolutely looked like a Cummins, and even the part numbers were similar, but since the gasket was the major problem to find, and through bitter personal experience, I nowadays always go with new gaskets (at least in critical areas,) I sucked it up and waited a month or so. But thanks for confirming my suspicion, and next time I need parts, I'll try "generic Cummins".
Well, guess what part I was able to find when the water pump went out last spring? Yep, when I bought the water pump, the place I bought that had both hoses, so I replaced them at the same time, (since I had to replace the coolant, what the heck?) Since that was a month after replacing the fan belt (which was a much more major operation than I would have suspected), I had already learned that if you have to take things apart to replace a simple wear part, replace any other "wear parts" that require the same disassembly.