Regarding the oil cooler: I think the oil pressure is always higher than coolant pressure, which means you end up with oil in the coolant system when an oil cooler fails.
It seems that your coolant is going somewhere, I would pull the valve covers, pressurize the coolant system, and see if you can pinpoint where the pressure is going. If it holds pressure, I would plug in the block heater and see if warmer coolant makes a difference.
Good luck.
It seems that your coolant is going somewhere, I would pull the valve covers, pressurize the coolant system, and see if you can pinpoint where the pressure is going. If it holds pressure, I would plug in the block heater and see if warmer coolant makes a difference.
Good luck.