Honda Accord oil in radiator

[BobM]

I bought a remanufactured engine for my 1999 Honda Accord from a reputable company with a three year warranty. My mechanic installed the engine and it was running great. Then I noticed it was using oil and checked the radiator and it had plenty of oil in it. He took it back pulled the head and the head gasket wasn't blown and there are no visual signs of cracking. He is thinking that the oil port where the oil pressure switch could be cracked but its hard to tell. The company where I bought the engine are not to much help so does anyone out there have any other ideas why this is happening. Thanks