Ataman AP-16 Can't fix a leak...HELP!

[far_shot]

My Ap-16 developed a leak that won't stop with new o-rings installed. The leak is between the frame and the plenum(see pictures ). Surgically cleaned and lubed, silicone greased the new 0-ring(as always) and it still leaks in the same place. Magnify shows no voids,cracks or any damage on the sealing surfaces. Rotated the plenum 180° and still leaks in the same spot on the frame. Nothing changes the rate of the leak. Tried a fatter 0-ring...no change. I have replace the 0-ring 5 times so far and I am barking up the wrong tree....but there is no where else that leak can come from. Has never been dropped where it might damage the thread integrity or 0-ring bore. Buna 70 0-rings is what I used.

I don't want to send it in because I sent it in twice for magazine indexing problems under warranty and they never got it fixed...so I fixed it myself with silver solder on the magazine paw. That paw was what I thoroughly explained to them as problem was when I sent it in...it was simply short cycling the magazine. $ wasted on shipping and insurance
I worked with industrial hydraulics and pneumatics for decades with no problems in fixes...but this one has me flummoxed.../

 

[allenbowles]

what size o-ring are you using??

 

[allenbowles]

looking at the drawing # 74 -19x1.5 o-ring (just in front of trigger) may be what you need???

 

[Motorhead]

With some 400 / 600 wet dry Polish up the sides and bottom of the O-ring groove, then do the same to the bore surface where the 0-ring is in contact.

 

[far_shot]

These are the o-rings for the AP-16

5x1.5 0-ring

3.5x1.5O-ring

5.5x1.5O-ring

13x1.5O-ring

8.5x1.5O-ring

19x1.5O-ring

They are not shown in the parts diagram with a number assigned to them and are only listed at the end.

# 74 is actually a screw.

13x1.5O-ring is used on both ends of the plenum (#18 accumulation chamber)
The original 0-ring and all the ones I installed, all have been deformed into the groove as expected when removed.I'm leaning towards a microscopic crack in the frame at the threaded hole There is no other explanation for no change in the leak size or source position

 

[rwsmike]

I have two atamans and PA said they are simple to work on but keep in mind they can reseal it for you also...a few yrs back they resealed a aa 400 and it only cost $75 which I thought was ok .



..

 

[far_shot]

Went through the pistol again tonight. Polished the groove, regardless that it looked perfect. Polished the frame bore and assembled with another new 0-ring. Yep, no change and started to leak at 40 bar. Picture is the point of the leak. Never mind the threads. They are bright and clean....camera doesn't see in dark holes.Sent PA an email asking for price of a new chamber. Sure hope it's not the frame with a micro crack.

 

[Odoyle]

I would first try and replace the o-ring with a fatter one lubed with divers silicone grease.

If still leak...

Try cleaning all surfaces and making a gasket like the Tuxing compressors use.

Like a head gasket.

 

[far_shot]

SUCCESS!....but not what you would expect for the fix.I was pretty sure the frame junction 0-ring was not the problem and had to convince myself. Cleaned it all up(AGAIN) and put a light smear of silicone oil on the 0-ring and put a coating of red grease in the frame bore....thinking the leak, if it was the 0-ring, would carry the grease to the exterior point.Still leaked and it didn't move any of the red grease. Next was to make a thin plastic gasket to sandwich between the frame and plenum. Still leaked as always and the thin gasket exposed a tiny bit of the through Allen screw hole. Hmmm, the leak is coming through the Allen screw hole....but how?
Picture is the gasket.

So I separated the regulator body and the small regulator piston 0-ring was hard and broke when removed. Fortunately it's the same as the probe 3.5 mm 0-rings and the valve plug 0-ring. Replaced it and screwed the air tank on ,,,and leaked a fierce amount of air. Back apart and found the the plug seal on the end of the piston had a tiny divot blowed out of it. Apparently you should not remove a charged air tank as that (I think) was what damaged the plug seal with the 300 bars of air blast. I could not pick it out to turn it over to the good side...it must be glued in or stuck....so I used a stone and polished it down till the divot was gone. As long as I'm here, I removed the piston and found the big end o-ring as hard as plastic Crap, I doubt I have that one in my 0-ring collection from left over industrial repairs........but I DID!


Yeah,I have a lot of 0-rings

Greased it all up and assembled AGAIN. Charged up and NO LEAKS! Some how the big end of the regulator piston 0-ring leak was making it's way to the long assembly Allen screw and following it to the frame junction where it could escape to the atmosphere. What a damned dealio!

50' bench rest and 50' off hand..........running great again

 

[Odoyle]

Whew! 

 

[Hapo]

...now Hapo scared...

 

[Geordie]

I've signed up for the sole purpose of saying a big thank you to @far_shot for this post - My AP16 had the exact same fault with the leak looking like it was coming from that spot against the frame. I changed the obvious seals but would never have thought it was coming from the rear of the regulator via the allen holes. I changed that same seal on the reg piston and my gun is now working perfectly.

Thanks again
Dan

 

[Cayenne2018]

Thank you all，My Ap 16 have the same problem，I changed lots o rings ，but the problem was not resolved.
which part of the O ring need replaced？

 

[Airgun-hobbyist]

Thank you all，My Ap 16 have the same problem，I changed lots o rings ，but the problem was not resolved.
which part of the O ring need replaced？
View attachment 431158

His leak was in the regulator and piston o-rings, not on the main cylinder sealing o-rings.

 

[Cayenne2018]

View attachment IMG_20240202_192545.jpgthese two o ring?

 

[Cayenne2018]

am I right?

 

[Cayenne2018]

THANKS!!!!
I did it!
no leak now!

 

[Cayenne2018]

View attachment IMG_20240202_200921.jpgthank you bro