If it's milky (indicating an emulsion) and brown I'd say your getting some oil into the water jackets in the engine block. Is there any white smoke out the exhaust? This would indictate that the engine is burning coolant as well, meaning coolant and oil are mixing both ways. I don't know about the 850, I've never had a head off one of these cars and I've heard there is no head gasket per say, but in every other engine I've worked on that would indicate either a blown head gasket or a cracked head. In either case you might see some external leakage of oil and/or coolant somewhere on the motor itself. All in all it's not a good thing, either case would require at least a new head. Hope that no damage was done to the bottom end of the motor by excessive coolant in the oil, which would mean a whole new engine. I would get someone to look the entire engine over pretty quickly.