First thing I did was wrap some paper towels around anything I thought might be producing a leak. The biggest offender was the cap on the expansion tank, and that wasnt producing a whole lot. My thinking now is that when I have opened the tank, a small amount ran down and filled the voids in the paint on the HEX, and when I got back there to clean things up, it looked worse than it really is. I'm still going to pressure test it. It could also be as you describe, loose clamps so I'll check those as well. Like I said, I watched the coolant levels and they were rock solid all summer. May be she's a FL girl at heart and doesnt like the cold!