S410 FAC air leak from cylinder?

[wild]

Hi all,

I recently (well, a couple of months ago) replaced the seals on the filling adapter for my S410 FAC. This included taking the actual valve out and replacing the small S327 o-ring. Seemed to all work fine at the time and shot well, held pressure.

Skip forward to today, and I took it out this morning, lined up a rabbit beautifully, pulled the trigger and, er, the pellet pretty much dropped out onto my feet. I checked the pressure gauge and the cylinder was empty (<50bar), which I thought was a bit odd.

So, I dutifully refilled the cylinder, no problems, up to 180. Took it out again, took a test shot and all of a sudden I could hear all the air escaping. I checked the filling valve, but that seemed fine. I then felt with my hands that the air was all rushing out from a small spot between the metal of the cylinder body itself and the barrel/cylinder collar. The air leaks until the cylinder is totally empty. When attempting to refill, the air just leaks out again.



I've marked the spot where air is rushing out between the arrows.

Can anyone advise what the specific failure is here, and does it mean a new cylinder or is it user-serviceable?

[Roger5]

Just replace the o-ring seal RN234 probably knackered Rog

[wild]

Cheers Rog. Yea, judging by the state of the others I changed when they came out it will be. I'll give that a try.

One day I'll have them all changed. One day.

[wild]

Hmm, Any idea how I get to it? I've got this far, but not sure how to get the end off the cylinder? Is it just an allen key in those holes below to take that end off?



Or is it more involved?

[wild]

Looking at the parts diagram, the end (S491) looks like it screws right off, but I'll be blowed if I can hand turn it.

[Roger5]

xtxair.com he does a tool for undoing it's just called a fill valve tool, £12 I think. Rog

[wild]

Thanks Rog, here's the link https://www.xtxair.com/air-arms-s400-s4 ... valve-tool

Just watched the video too here: https://www.youtube.com/watch?t=&v=-wP6YXXEsPg, which was useful.

[wild]

Just as a follow-up, it was indeed the end O ring in the cylinder - finally managed to get the cylinder end off with the help of that valve tool from XTX (Christ it was still stuck on tight though! A soft-headed vice, large spanner and a lot of swearing were finally needed to get it out!) and replaced the seal along with a bit of silicone grease and we're back in business again. Checked the O ring at the start of the cylinder and that seemed fine, which is good because I didn't fancy taking it apart further to try and get that out and replaced - it was a bit tight.

Thanks a lot for your help Rog. Much appreciated.