I've got the leak in my Silca floor pump isolated. (It's the Super Pista, the old version with wooden handle but only one footrest - the updated model has two places for you to step on the base and hold the pump down with both feet.) It's not a problem until 80 PSI or so, but a little air leaks at the fitting between the bottom of the long tube and the brass piece to which the pressure-gauge and tube connect. I've tightened the base (which holds this joint together as much as possible, having put a bit of bearing-grease around the joint first. It's possible that there's not supposed to be any grease there to help the seal (i.e., the design is that the brass would deform under hard tightening pressure, and thus seal the connection), so I'm going to take it apart again and try cleaning the grease off. Any thoughts in the meantime?