...as you tighten the tube nut it squeezes down on the line and seals it off. I THINK it depends on what your screwing it into for it to work like its suppose to.......someone correct me if I'm wrong.
For what its worth. I bought 10 of those threaded tube nuts from NAPA so I'd have extra's. When I hooked up my guage it took me TWICE cutting the ends off and using a new nut before I ever got it to quit leaking a drop every now and then...... I could never tell if it leaked around the threads or leaked between the copper line and the tube nut.
I'd be interested in what others have to say about this...if they had the same leaking problem.
