The radiator on our 2011 CX-7 has a small leak near the filler/cap spout, on the piece that sticks out toward the engine. This section has a plug which looks like it may have been snapped in when manufactured, and perhaps has a seal of some kind inside, but does not seem to be removable or repairable. Does anyone know what that is for, and if there is a way to repair a slow leak there?