Stuck Valve?

I need your help guys. I was just shooting my SS and the valve started leaking air. My groups started getting weird and then I noticed the constant hiss. When I opened the breach and put my finger over the top hat the hiss stopped, so I figured it was just a slow leak perhaps related to the outdoor temp (about freezing).

When I came back in and tried to fill the tank the valve seems like it just will not seat closed. Might it be frozen with water vapor? I filled to ~3 ksi, but when I opened the purge valve the whole tank dumps. 😯 I Actually tried twice, what a waste of air!

I compressed the top hat carefully and it seems to be binding and tight. It’s not smooth at all and does not want to return to the closed position. I’m hoping it’s just frozen, not bent or a burr. With the exception of some baffles in the shroud my SS is stock with about 1,500 pellets through it.

I’m letting everything warm up with a constant ~2.8 ksi on it to see if the valve will seat. Any advice? I’d sure hate to go back to a pumper if my Talon is borked!

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The conditions leading to my leak are almost identical. I filled the tank 4 days ago, shot maybe 7 times out of my back porch into my lighted shed just to test the new tank.

Today I went out, 25 degrees F and shot about 30 times, started hearing the hiss.

After the gun warmed up, it was still hissing. Called AF and they told me to try a plastic hammer and gently hit the tophat a few times. I did this and the leak got worse at first, but after about 10 strikes it stopped.

I have refilled it to 3000psi and shot 5 times, still no leak. Keeping my fingers crossed on this one.

I sorta followed Tony’s advice.

When I pulled the top hat out (After venting ALL pressure) the knurl at the bottom of the shaft bound up a bit in the brass part. I got it out, but it scratched the the bore of the brass part. So much for smoothing things out…

I strongly suspect that AirForce assembles the knurled shaft from the bottom. Knurling can certainly exceed the diamter of the shaft, and thus bind in the brass bore.

I skipped polishing the shaft and re-installed it with much care to avoid more scratching. When “fully” inserted I gave it small whack with a piece of wood to seat it. I want to emphasize small whack here – don’t bend the top hat shaft.

At the end of the day I think my leaking was caused by condensation freezing in the valve. I was filling in my warm cellar perhaps a bit quickly, and then stepping outdoors where it was about 15º F to target practice. After doing this about 3 times the problem started.

So far my valve seems fine. I haven’t been shooting much since then though because of the weather / time change. Good luck!

Lost Sailor, did you try this advice? I am experiencing the same problem and would rather hear if this worked before I try it.


Thanks Tony, I’ll do exactlly that.

Sounds like your valve stem is binding in the brass insert.

With an empty tank, pry out your top hat and valve stem with a screw driver. It is press fitted in a delrin valve seat/seal.

Chuck the tophat in a drill press or portable drill and spin while hitting the valve stem with 400 then 600 grit paper. You want the smoothest finish possible.

Clean, reseat the valve stem and dry fire a couple time with PW maxed out to fully seat.

Fill to 2000 psi and check for leaks using soap bubbles.

Any problems, send it to me and I can turn it around in a day or two.
Good Luck,

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