I'm on cooling elbow for the leak and you should know that when pressure pushes out coolant, that something has to replace it..even if it's air. Air however compresses easier than liquid, so it's very doubtful that something is pushing coolant to the overflow.
My feeling is start with coolant elbow, have your cap pressure tested and before you start.. pull the cap, top it off and let it get up to temp.. if you see flow..the pump is fine.

Scotty.. aluminum has a tough time rusting out.