Was playing some hardcore doom eternal. The like to the left is the actual inlet from the radiator below, the line in the middle bottom is the drain line (loops around back). Up top is the fill and an optional inlet (with straw that goes down into the res) - and water has started to fill that. At one point, it filled enough to actually push out around the plug and leaked into the top hat of the res (Corsair XD7). Do I have the wrong kind of plug up there? Too little water letting that air expand and push it up the tube? Tried opening the fill (as you can see) and that didn't change it. Letting the system cool a bit before I touch it.