I would call it the "treadle valve". 1971 Brockway 358. It USED to be that it would leak in extreme cold(<20*) then once it built some pressure it would stop. But now my truck has a pretty decent air leak from what I would call a treadle valve, under floor. I assume it is a dry seal and cheap fix. Anyone want to guide me, tell me, correct me? I'm going to get starteds on it in the next couple days. If someone has a cheap, easy fix... I'd love to hear it.
Please and Thank You.