2004 Silverado 1500 5.3 Z71 is leaking coolant AFTER the engine has cooled down and not noticed under pressure while running and not until engine cools down. Seems to be coming down from passenger side as seen in picture up above that black plastic clip. Thought it might have been gaskets for the water pump. New ones installed and still leaking. Weep hole is dry after running and engine still hot. Seems like if it was coming out of that, it would happen while under pressure. Could it be the thermostat gasket? Anyone had this happen with their Silverado?