tan62,
The only place in the head area under pressure is the rocker arm center oiler. This oil comes from a tube connected to the cam brg oil supply. The tube runs externally through the push rod area to a connection on the bottom of the head. Another tube runs from a connection on top of the head to the center oiler. The passage through the head COULD leak into the water jacket through the head gasket, but I would doubt it. A incorrect head gasket could have been replaced with another incorrect head gasket, but I don't think so. As the engine is shut off and loses oil pressure, coolant pressure would remain. Any oil/coolant breach would be a two way street. I would tend to think that, after cleaning up the coolant, the problem might go away. Keep in mind I haven't even seen the inside of a 235 since I was in high school and retirement isn' too far off!

Stuart.