Hope someone can help me on this problem. About a year and a half ago, I lost coolant with a hose on the oil cooler near the oil filter. Anyway the engine got overheated and I did not see the temp gage right away. They ended up taking 8 thousands off the head. A while later, not sure of time at this point. I started getting oil in the expansion tank. I did use die to find out it was not transmission fluid. I have sent all the fluids through to have tested. I have flushed the cooling system several times. Cleaned the expansion tank alot. Thinking that it was just oil left over from the blown head gasket. I have tested the turbo with R-22 pressure, 125 to maybe 150psi and no leaks. Let it settle with temp and pressure and had no loss. Did the same with the oil cooler down by the oil filter. That was last summer. Just the last week, had a mech. do the diaghram in the turbo. He said it was falling appart. He also did a boost test. I have called a turbo shop here in Des Moines, Ia. They do not think it could be the turbo. It would have to be a casting crack. I called a machine shop that redoes heads. If I have a oil port maybe cracked. Plenty of power, Just a small amount of oil in the expansion tank. The machine shop thought it could be a oil cooler down by the oil filter. He has heard of a few of those going bad. Can anyone give me an idea of which way to head to find out if this oil is coming from the turbo or head or the oil filter. Just looking for some suggestions. Note, I just had to retire my 245 with close to 400,000. This 940 had the turbo rebuild about 3 years ago with new bearing etc