"if I don't add the coolant back to reservoir she does not leak."
Almost has to be overfilling. Pretty much anything else that would cause a leak would leak no matter what the coolant level was. At least until the engine ran almost out of coolant.
Just for the heck of it, while you're poking around looking for the problem, I recommend you take the air bleed line between the manifold and the expansion tank apart and make sure the orifices and the tube itself are clean and not plugged up.