I have purchased the complete valve assembly from both Prevost and an independent supplier, depends on when I need it mostly. Obtained a spool and operative (from a supplier Prevost does not sell parts)

I only have the parts for an emergency, don't think I will ever use them though, now have new valves for that.

After disassembling several it is apparent to me that it is not wise/cost effective to attempt the repair unless you have a lot of time and are willing to test the repaired valves before use.

Used valves corrode internally from airline moisture and the corrosion creates a rough surface that wears on the rubber washer that outwardly looks like an ordinary O-ring thus destroying the seal. This is known as a LEAK! LEAKS are also caused by damaged washers on the valve spool, this caused by careless assembly or perhaps assembling with a damaged washer when new.

The images are of a spool assembly and a damaged washer, third from the left!

Note the small notch in the washer.

NORGREN SPOOL WASHER.jpgNORGREN SPOOL VALVE.jpg