engine (not an HG). What about the water pump weap hole? Dripping down from there? Or the upper radiator hose - which is the hose that usually goes bad due to engine movement (fyi: I had a new 1yr old upper hose do this). Also possible the radiator has a pin hole leak but kind of doubting that -- since it should be a easy to spot....
However - not to say there isn't another issue too but find this one first.