Advice wanted for repairing Marauder air leak

Forums PCP Airguns Advice wanted for repairing Marauder air leak

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    PHeplerNC
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    I would like your advice, suggestions, and video links on how to repair a air leak on my .177 Gen 1 Benjamin Marauder. 
    The air leak is more noticeable from the breach and out the barrel at lower fill pressure- 2200 lb and lower. I’ve only been in the PCP game for a year or so, but I’m assuming it needs new o-rings on the valve. I’ve never pulled the action apart down to the valve but am more than willing to fix it myself. So if you have some favorite video links or advice I would love to hear from you.

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    JohnL57
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    This is a really good video by Hajimoto-he covers all the steps and gives great advice on the details!
    https://www.airgunnation.com/topic/mrod-gen2-weight-loss-program/
    Marauders are easy to work on, just be organized and take your time.
    Good luck!
    John
    PS-Safety first! Make sure you degas the gun before working on the air tube!

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    PHeplerNC
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    Thanks John!

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    PHeplerNC
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    Also wondering if it could actually be the valve stem that is the problem. Not sure what happens if/when those go bad. Corrosion? 

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    Rj
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    Sounds like the poppet isn’t sealing on the valve seat. May just be some crud in there. You’ll have to get it apart and inspect.

    Find out what o rings fit the valve and the gage block and stock up on them. Your bound to tear one or two your first time putting it back together.

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    briansmith
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    as mentioned John.  Look for videos on utube.  haji and others have some great informative info on there.  Brian

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    Brian10956
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    Be careful it’s real easy to mess up the orings on the valve and the gauge block . When you reassemble the rings get cut up by the holes in the air tank as they slide by. So if you change the orings buy extra you will need them

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    PHeplerNC
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    Thanks! Someone also suggested a drop of silicone oil in the fill port to keep everything lubed up.

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    Kinetic45
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    And the solution to cut o-rings is to GENTLY take a rat tail jewelers file to the inside edges of the holes in the airtube and chamfer them.  It only takes rounding the edge a tiny bit to stop cutting rings if you push the valve in til the o-ring is starting to get caught and use a flat blade screwdriver or like tool to ease the ring down into its slot as it passes the back edge of the hole.
    I have used a mototool but I have used them for years and know how to hold back and not remove too much.  a novice should use the file and take it slow.

    I also smooth the inside edge of the hammer pin slots as per videos on youtube to prevent scraping/dragging on the hammer like some out of the box marauders do.

    Safety – Remember to THOROUGHLY CLEAN the tube of all shavings before reassembling the airtube and do not use petroleum lubricants inside where pressure is… use some silicone chamber oil.

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    Crusher
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    When you take it apart, if there is crud in the valve, you should inspect your air supply. You may be getting a little water in the tube. That happens most often with pumping, but CAN happen other ways as well. Just something to think about while you are cleaning and checking things.

    Crusher
     

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    PHeplerNC
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    All good stuff. Thank you!
    I use a SCBA tank filled at my local dive shop for air. But moisture can still get in there I’m sure. Moving the gun/tank from hot to cold, to hot, etc.
    I tuned it again this afternoon and it has stoped leaking for now. I’ll shoot a field target match with it this weekend and see how it behaves.

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    PHeplerNC
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    Thanks for the advice and suggestions. I dove in deep!Found badly stripped threads in the gauge port- enough to have metal bits flaking off. Also found a very stretched o-ring on the valve. The Valve stem looks generally OK where it seats, but a little rough around the edges. I ordered a new gauge port, set of rings, and valve stem.

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    kkarmical
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    “PHeplerNC”Thanks for the advice and suggestions. I dove in deep!Found badly stripped threads in the gauge port- enough to have metal bits flaking off. Also found a very stretched o-ring on the valve. The Valve stem looks generally OK where it seats, but a little rough around the edges. I ordered a new gauge port, set of rings, and valve stem.

     

    
That looks like some sort of corrosive matter came in contact with your gun.  You mentioned silicone lube of some sort, what kind are you using?  
    Good job on the tearing gun down, I remember my first time, and thinking is that it.  Now being able to take it down if you ever choose to upgrade parts it’s no problem.

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    PHeplerNC
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    Not sure what the corrosive “gunk” is on the gauge port. This is the first time I have opened this gun, so I’m not sure what was done last time it was serviced. I suspect some sort of sealant was used because of the stripped threads. I always noticed how the gauge was slightly angled- because of cross threading. 

    I will be using a little 100% silicone grease when my parts come in. Picked some up from a scuba dive retailer. 

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    kkarmical
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    I’ve tried a few different dive silicon grease/lube products, then I had a very slow leak that I had trouble figuring out.  But during the process I switched over to this vacuum grease, its the best stuff out there, you can feel the difference when using it vs regular silicon grease/lubes.

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    PHeplerNC
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    Thanks for the tip!

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    PHeplerNC
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    Question- what should I use to clean the internal parts like the valve and tube? Alcohol?

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    Kinetic45
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    Some alcohol may have too much percent of water in it in my opinion as occasionally it will cause flash rust on bare ferrous metal (1 or 2 % of the time but do you want to risk even that low percentage?)
    And some silicone greases it does not work too well on, just won’t cut the mustard (haha)… I use acetone I buy at the hardware store in the paint section (do they still sell it in Kalifornia?)
    Just remember that HPA and flammable solvents do not mix… if you use a flammable to clean, then you should use a non-flammable to flush out the trace hydrocarbons.
    I have used spray brake cleaner often and even carb cleaner but make sure its not the ‘lubricated’ kind.  NOT recommending it but I used to use kerosene/diesel to clean then flushed with brake cleaner back years ago when acetone was harder to get.

    And ALWAYS remember to do this in a well ventilated area (outside if possible) because I had a friend pass out and die in 1989 from fumes in a small closed room.  Changed how I do everything from then on.

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