Benjamin Maximus Foster fitting repair?

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Update: I removed the foster fitting from the rifle and was confused to see a screw driver fitting on the inside of it. Turning it did nothing. I finally figured out to grab the fitting slot with a tiny needle nose and pulled it out. There's a whitish yellow O ring in it. Looking down into the hollow portion of the foster fitting, I could see little pieces of what looked like metal chips - very small in size.
I completely cleaned the fitting inside and out, and sprayed the o ring / plunger assembly using my gun cleaner/lubricant. The lubricant dries after a minute or so.
I put it back together and used white teflon tape on the threads, tightening it as much as I though was good.
End results? The leak is much better than it was before although it is still losing about 1/2 a line on the pressure gage every 24 hours. I guess I'll have to order a new foster fitting because I don't know what else to do.
The only thing I can think of is to buy some silicone grease and use a little of it on the foster fitting o ring and plunger instead of the spray lubricant I used.

Any thoughts? I'm so close to fixing it.
One thing I did not do was to remove the o ring from the plunger inside the foster fitting. I just sprayed it, wiped it off with a lint free cloth, and put it back in.

Thanks!
 
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Given it's still leaking after reassembling, the issue is probably the O-ring. As they age, they will frequently develop a slow leak. The other clue is the "whitish yellow" which describes a polyurethane O-ring that is aging.

Crosman typically uses a -006 size on their Foster check valves. BTW, Buna-N is every bit as good as polyurethane for this application.

And as Steve said, only silicone oil (e.g. RC shock oil) or grease (e.g. automotive dielectric grease).
 
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WN0912 said:
Update: I removed the foster fitting from the rifle and was confused to see a screw driver fitting on the inside of it. Turning it did nothing. I finally figured out to grab the fitting slot with a tiny needle nose and pulled it out. There's a whitish yellow O ring in it. Looking down into the hollow portion of the foster fitting, I could see little pieces of what looked like metal chips - very small in size.
I completely cleaned the fitting inside and out, and sprayed the o ring / plunger assembly using my gun cleaner/lubricant. The lubricant dries after a minute or so.
I put it back together and used white teflon tape on the threads, tightening it as much as I though was good.
End results? The leak is much better than it was before although it is still losing about 1/2 a line on the pressure gage every 24 hours. I guess I'll have to order a new foster fitting because I don't know what else to do.
The only thing I can think of is to buy some silicone grease and use a little of it on the foster fitting o ring and plunger instead of the spray lubricant I used.

Any thoughts? I'm so close to fixing it.
One thing I did not do was to remove the o ring from the plunger inside the foster fitting. I just sprayed it, wiped it off with a lint free cloth, and put it back in.

Thanks!
Click to expand...
I dont use the white teflon tape any more, I use to use it and sometimes i have to tape it really thick and still having a small tiny leak, the i switch to the yellow or pink one, and in one try its much thicker its seals it much better for me and no issues at all
 
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