It has been a while but I believe there is a valve that shuts off the flow while parked. It wouldn't be an absolute seal though. Try hooking it up to a vacuum supply and see if it hisses.


1951 GMC 1 Ton Flatbed -- It is finally on the road and what a great time I have driving it!
1951 1 Ton Completed


My Chevy Master 4 Door is on the Road!