Yeah, wierd little thing. . .It makes this sucking/slapping noise as it is working. The vacuum pulls on a diapragm inside and moves a valve that lets it back to the starting position. If I remember correctly, the diaphragm movement also is pumping a bellows or valve that fills the tank with compressed air. It really does sound cool when it's running, but I don't know that I want to listen to it for the duration of a road trip!
Mine just never built up enough pressure to make it worth the time to fiddle with it any more. Hopefully David's works better.
Craig
