After figuring out that ALL of my valves were leaking, i decided to get midevil on their asses. I took them all out, and gave them all a once-over.
If you don't have a valve wrench, I found that a pipe wrench and a gentle touch work very well.
My springs had been compressed down to about 3/4 inch long. I gradually strectched them up to 1 1/8-inch. There's more closing tension now.
I checked at Napa auto parts, Tractor supply, and Lowes, but I could not find a replacement for the main gaskets. Mine were starting to get hard and they weren't sealing. So I took them out of the valve, and soaked them in water with dish washing soap, and scrubbed them with an old toothbrush and a scotchbrite pad. I then soaked them in WD40 over night and they got some of their rubberyness back. I heard that brake fluid or transmission stop leak fluid might work even better.
If any one knows where I can get replacement gaskets around town, I'd love to hear it. I was told that my local hydraulic hose repair shop might have them.
The Valve are completely different now. I don't know if they are back to 100%, but they must certainly be in better shape than before. I will install them tonight and let you know how they turned out.