I have a small coolant leak at the back of the engine above the starter. Maybe a drop every couple of seconds. Hoses look good, I can't see the freeze plugs, but I'm thinking head gasket because I can see a little wetness by the back corner of the head. I just changed the oil and it looks good, not milky at all. The engine was rebuilt to a 331 in 2006 with only 9,000 miles driven on it. It has been running great. What do you guys think about those radiator leak additives? Do they work?