That vertical pipe sounds like part of the crankcase breather system, as the kidney box is around that area.
If it is the tank leaking, and not a bodged loose clip to stop the blown headgasket showing, then just get it welded, there's no reason they should leak, as such little pressure in them, but a lot of bodges done to cars with head gasket trouble to disguise it, hope your's isn't one of them.
tabetha