The only leak check you can do is when you have it together and you use the check plate bolted to the case where the valve body bolts on. You apply uner 20 lbs psi (if I recall correclty - don't use too much air pressure or you wil blow the seals) You should hear a good solid piston engagement. As you hold the rubber tipped air chuck to the plate, with air off, when you remove the chuck you should feel and hear the air being pushed back as the piston collapses back. You only need to briefly tap the air chuck for air. If you hear a hisstin sound an no pressure is being held, it could be bad or misinstalled piston seal, cracked housing, etc.
Eliminates the guesswork for sure.
Bob
