[77newell]

On my 77 coach I had an instance when I shut off the supply valve but left the return side valve open. The supply side valve dripped from around the stem when it had never leaked a drop previously. When I re-opened it later it stopped leaking altogether. I tried tightening the nut around the stem but it wouldn't budge. I tried loosening it and found an odd packing under it that only sealed when the valve was completely open so that a ring on the stem rose up against that packing. I don't know if the valves on that coach were unique or common to many coaches.

If I closed both valves so that there was no pressure in the loop neither valve leaked.