Engine oil seems clean-- no coolant-- and was still hovering around full on the dipstick.  The level of the coolant was also where it should be.  Based on other forum posts, I suspected the engine oil cooler as the culprit.  I drained fluids and removed the oil cooler and took it to the radiator shop for testing.  Rad shop just called and said they pressure tested the cooler and can't find any leaks but told me it's possible that it could be leaking only when hot, which doesn't always show up in their testing??  I thought about just replacing the cooler to be sure but checked with the Agco dealer and was told that the cooler is NLA.

Now I need to figure out where to go form here.  Should I dig deeper into the cooler or am I possibly looking at a head gasket or cavitation issue?  I thought about bypassing the coolant lines around the cooler and running the engine up to temp to see if any oil comes out the coolant tubes.  Suggestions on further troubleshooting steps would be greatly appreciated.  Thanks in advance!