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o-ring replacement benjamin marauder .177

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jackrterrier

Member
Apr 18, 2018
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Trying to replace the 4 1763-026 o-rings that go inside the pressure tube - 1 on the valve assembly, 2 on the gauge port assembly, and 1 on the fill adapter assembly - I keep chewing up the o-rings on the threads at the end of the pressure tube, where the fill adapter screws in. Especially the 2 on the gauge port assembly.

I get the gauge port assembly about half way in, then it gets stuck, and it takes a lot of force to get it to go in. And when that happens, it shreds the o-rings on the gauge port and I see little black pieces of the o-rings when I look down the tube.

Anyone have any advice on how to get these back in without destroying them? Going through o rings like it's nobody's business and about the give up. I've been using general purpose lithium grease but have ordered some diver's silicone to use instead.

Do I need to sand down the threads inside the pressure tube or something? Any help/advice appreciated. I've got chipmunks to dispatch asap!!

Thanks
 
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What type orings are you using? I find the basic ones you find at the hardware store tend to not be that durable, whereas if you're using 70 duro+ orings and add a little vacuum grease or divers silicon it makes it over the threads pretty easily. Order some good orings, I use the Oring store but there are a couple different ones to choose.
Make sure and cover the gauge port hole as it chews up orings too. You can cover it with your thumb or they make a thing to cover it.

 
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Jack,

Definitely use a lititle silicone grease, and quality o rings, as mentioned above. I get my o ring kits from Archer Airguns, and he makes a great little device that plugs the holes by the valve and the gauge block, so the o ring passes by the hole unscathed. Well worth it. Some guys have disassembled the entire gun, and have gone inside the holes that o rings go past with a fine stone on a Dremel tool. I have done this as well, and in conjunction with the Archer tool, it's smooth sailing. Do not use Harbor Freight o rings, they are too hard of a rubber, and not pliable enough.
In a week or two, I'll be totally tearing down my Marauder and rebuilding it for the upcoming Field Target season on my Field Target Tech Channel. I'll have both the entire disassembly and reassembly on 2 separate episodes.

Tom Holland 
 
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I'll second that advice about getting that little device to help with the gage port hole from Archer Airguns. I have had to put the valve and gage assembly in several times on the same rebuild because I didn't have it lined up correctly when I inserted it in the end of the tube and have had no O-rings messed up ... even though I had to put the same o rings in several times. When I put the valve and gage in the tube, I not only put silicone grease on the o rings ... I put it on the threads also ... in fact I put more on the threads than I do on the o rings. You can get all the o rings you want from Archer or you can use the o ring store 

​It wouldn't hurt to try and shine a bore light down there and see if there might be a burr somewhere around the threads
 
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thanks for all the suggestions. the problem starts at the threaded end of the pressure tube. I think on the gauge port assembly, when I push the first o-ring in past the threads, it gets hung up and comes out of the channel where the oring sits, and then gets between the inside of pressure tube and the outside of the body of the gauge port assembly. Then the back end of the gauge port assembly where the 2nd o ring sits won't go in without a tremendous amount of force. That's when the orings get shredded.

Has anyone ever tried to sand down the threads inside the pressure tube? What would I use for this? Seems like the pressure tube would still hold air since the oring on the fill adapter is past the threads...

the gauge hole is not as much of a concern, I took a hand held deburring tool to it. I also temporarily put the hammer assembly in backwards and use the screw to hold it in place - it acts like a backstop to keep from pushing the valve assembly past where its supposed to go.
 
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Jack, 
Some guys have disassembled the front fill fitting, and deburred the threads with a fine piece of wet or dry sandpaper, about 600 grit. This should only be done when the entire tube is empty!!!! If not, the grit will surely get into the regulator (If equipped), the gauge block, and eventually the valve. After lightly sanding the threads, the tube should be cleaned thoroughly, and light coats of silicon grease where appropriate. In my experience, if you coat the threads and o rings with grease, you can slowly squirrel and manipulate the fitting past the threads with little damage. Also, not all o rings are the same. Some o rings from different manufacturers, even though they are the same size, when carefully inspected, aren't the same size. They might be slightly thicker, or thinner as well. I use only o rings from Crosman, or Archer Airguns in my rebuilds. I've found that o rings, even quality ones from other sources will end up leaking after installation. Take it from someone who learned the hard way.

Tom Holland 
 
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Tom
Thanks, I might try the 600 sandpaper. The tube is empty so I'll clean it afterwards if I decide to do that. I bought o rings from 'captain o-rings' - they were crap, will never buy those again. this is what I've gotten the last couple of times:

https://smile.amazon.com/gp/product/B01N2QLN06/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

will look into getting them from Archer in the future.

maybe the lubricant I've been using isn't getting it done.

Again, thanks for all the advice.
 
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New question - I ordered a kit of o-rings, and there are several sizes. So I'm looking at the exploded view and partslist diagrams for the 1763, but of course, I can't figure out which o-ring goes where. Well, most of them I can, but not all.

In the diagram, part #10 is o-ring 1.5mm x 4.0mm, 1763-058 - where does this go?

Does it go inside the end of the barrel? It looks like there's a slot inside the end of the barrel where an o-ring could go. If so, any advice on how to get it in there?

I don't see one in there now, so it must have been blown out at some point.

thanks
 
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Jack,

There is an o ring at the breech end of the barrel, and you are correct in that there is a little step inside of the barrel, where the o ring should go. It depends on the caliber, the size you mentioned is for .177, if you look at the parts diagram from Crosman, they should list the size for the .22 as well. It's a little tricky to get it in there, you might need tweezers or a small pair if needlenose pliers. It could come out if it gets stuck on the bolt, if it does, do this.... I put a wipe of rubber cement on it, to keep it in place. Dries fast, the excess wears off with a few shot cycles, then you are good to go.

Tom Holland 
 
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Jack,

Sometimes there are spares, but not usually. When you buy an o ring rebuild kit, they give you ALL o rings in the set, and some are a mystery to where they go, and what they are for. You can order individual o rings through Crosman's customer service line. I just ordered a bunch of parts, and some o rings were on the list. I will be doing my reassembly of my WFTF PCP Marauder for Field Target this weekend, should be posted on my Field Target Tech Channel on U Tube by sometime Saturday.

Tom Holland 
 
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Jack,

Try what John said above. As you are putting air into it, cycle the gun a few times.... bolt back, forward, and pull the trigger, as air is flowing. This might have to be done several times.
Another possibility is that the hammer is adjusted too far, opening the valve which you do not want. You might have to back off on hammer spring pressure as well.
This could happen if the tune was right on the edge of the valve being open/closed, and when the gun was reassembled, it decided to stay open. If the valve worked before you took it apart, then the valve should work afterwards as well.....UNLESS...........
This is a Gen l Marauder, are you the original owner, and if you are, how many shots do you have ( I speculate that it is the original valve that came with the gun/ never been changed) through the gun?
Let me know, I'll have to give you an answer, after you answer my above questions.

Tom Holland
 
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Tom,

I'll try to answer your questions...
I am the original owner.
I have no idea if this is a Gen I marauder - how do I tell? (obviously I am a neophyte)
How many shots? I dunno, not a lot - 200 or less? It is the original valve.

I may have adjusted the hammer - I dunno, I really don't know that much about the guns (see above - neophyte). Hammer spring pressure? (duhhhh). Some pictures of these things would be great.

I decided to take things apart again (which I hated doing after butchering a bunch of o-rings), and took the valve apart. There was junk in it, and as well, the valve stem end (the plastic part) was starting to disintegrate. So I've ordered a replacement valve assembly from Archer airguns.

With the valve disassembled (spring out, valve stem out, valve cap off), when I plug up the valve stem hole and blow into the valve cap opening, I get air coming out of the 'port' on the top. even with the valve stem in and blowing again, still get air out the 'port' on the top.

Is there supposed to be an o-ring inside the valve assembly? I didn't see one of the parts diagram. Is there something inside that 'port' that is stuck?

I appreciate you taking the time to answer my questions, realizing that I have no idea (currently but learning) about how the air rifle's internals work.

 
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