I have a 3.1 buick century waiting for treatment of a simular sort. I imagine either the head gasket was changed out or it was not. Someone may have sometime without cleaning the coolant system out as well. The car runs very well with no indications otherwise of a current possible head gasket problem.

Citric flushes might be too agressive. First I want to find out if it is a head gasket or not anyways. So I will drain the current junk out and put water and liquid detergent soap in. Run for awhile and flush and repeat until it is nice and clean.

Perhaps then run a low percentage of water and anti freeze mix and keep an eye on it for a week or two. If it stays clean then put a normal mix of coolant in.

If not try to find out the head gasket that may have failed and change it out. At least on the 190 you only have one head. On the 301 it might be better for me to change the two out as preventative maintenance rather than just one anyways if it comes to it.

I do not unfortunatly know the past owner or have anyway of contacting him.