Help We Are Stumped!

[Rick Comenzo]

We need some opinions, I recently pulled a 3 cylinder 201 cu. in Ford diesel from a 555 loader, engine oil in the antifreeze(cooling system). After a complete rebuild, head and block magnafluxed, pressure tested by machinist, head milled, block decked, bored 20 over, etc. , the same problem has returned. Also had a small amount of coolant in the engine oil. This problem redeveloped after running the engine for 2 hours with no load. Pulled thermostat, reflushed cooling system, lost 1 quart of engine oil into the radiator. This loader has no oil cooler, and heater core was bypassed. We are stumped. Any ideas? Thanks in advance. Rick.