Help me find a leak in my Impact MKII please.

Forums PCP Airguns Help me find a leak in my Impact MKII please.

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    stoti
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    I got this Impact MKII in .25 caliber a couple months ago and have probably put about 2000 pellets and about 200 slugs through it total. A couple of weeks ago I noticed that after the gun sat overnight the pressure dropped about 5BAR from full, every night it dropped about 5BAR more until it got down to lower pressures and then it dropped less each night until it tapered down to 3BAR, 2BAR a night. Then it got low enough that it seemed to quit leaking when it got down to around 40-50BAR. I tried everything short of dunking the action in a bucket of water to find the leak. I started with detecta-leak on all the known spots, checked all the O-rings, took it partially apart to check more O-rings, etc… I've watched all of Ernest's videos multiple times, talked to Edosan, Ernest and Brian multiple times and can't find the leak. It's probably nothing difficult or too problematic but this is my first Impact and I am not as familiar with the internals as I should be. It's really not that big of a deal except that I'm OCD and I hate thinking about my gun having a small leak.

    The other day I started testing a bunch of Nick Nielsen's new slugs with great results but it was very windy. I wanted to continue testing on a calm day so I went out this morning to continue testing at 8am. I shot a couple of good groups with the 33.5gr slugs at 50 and 100yds, after 2 1/2 magazines, when the gun got to 155BAR, I decided to re-fill. I filled it, set it aside to load a magazine and when I went to chamber a round I heard a psssss sound coming from the breech. Oh, crap, not a slow leak anymore!

    I got my tools, pulled the barrel and determined the sound was coming from the transfer port area. What I want to know from you Impact experts is where you would start looking for this kind of leak or what it sounds like it might be? What's the simplest way to get at it? From what I described, does it sound like a problem with the C3 bumper, a different O-ring problem, the valve assembly somewhere, or something else? Does the fact that it was a very slow leak at first and where the leak is coming from even help give you any ideas?

    I have taken my Impact partially apart but never fully apart. I'm not afraid of disassembly, well maybe I am a little worried with a full disassembly because I don't have the specialized tools necessary and I don't want to damage anything because of it. The first time is always a little scary, even though it always turns out to be no big deal and easier than anticipated. I think I'll make some specialized tools as I go. I really need to be more familiar with the internals of this gun anyway! If I was familiar like I should be, this would probably be a 15 minute fix! 

    Anyway, any thoughts, ideas, advice or help of any kind would be appreciated. I'm on the remainder of my vacation for the next 6 days and would really like to have this fixed asap so I can continue slug testing while I have some time off and no honey-do-list! 

    Thank you in advance for your help!

    Stoti

     

    • This topic was modified 5 months ago by stoti.
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    heavy-impact
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    Sounds like the valve seat o-ring or the delrin valve seal.

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    TylerE.
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    That sounds like what my gen 1 was doing. I would shoot and then all the air would come rushing out the barrel. I bought mine used (very used) and after a complete tear down, thorough cleaning and reseal it still did it a few times. I would rapid fire a few times to try and clear any stray junk that got dislodged in the cleaning process. It has worked great since. So I figured that there was something that got stuck between the valve seat and the delrin valve piece. Good luck, hopefully you find it easily. They really are easily worked on, so long as you go slow and not force anything. 

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    stoti
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    Thanks guys, I'm taking it apart right now.

    Keep the help coming please!

    Stoti

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    AirSupply
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    If your sure if’s leaking through the transfer port then I’d say Heavy Impact is on the money. Problem is at the valve. . It would be very unlucky to have that happen after so little use I always just check the simple things first like is the gauge leaking.  

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    stoti
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    I don't know where in the transfer port, I just know that's where I can hear the air coming out of, so it could be anywhere inside there.

    So I just took the whole gun apart inspected everything and it looked perfect, including the valve seat o-ring…Like a new gun. I cleaned and lubed everything, put it back together and no leak???

    One thing I did notice when I was disassembling the gun is that there is a screw on the back of the block, directly up from the rear of the grip on the right side. It is 4mm and it tightens both sides on the plenum tube. When I went to untighten it, the screw was very loose. Like wobbly loose! I'm wondering if that was not tightened down enough, it would keep the o-ring from sealing properly and that was causing the problem? If not, maybe one of the O-rings just needed cleaning and lube? I don't know but I'm happy, just a little frustrated too, not knowing what it was and if it will do it again tomorrow? You know what I'm saying? 

    Like I thought, taking the gun apart was very simple and not nearly as scary as it looks. 

    Thank you guys. I'd still like to hear anymore thoughts or ideas that might help me down the road. I'm worried I'll go to shoot tonight or tomorrow and have it happen again.

    Stoti

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    AirSupply
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    👍

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    stoti
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    I just filled it to 250 BAR, let it sit for a few minutes and then fired a few shots out back…No leak! It cocks more smoothly now and just feels better. Although I haven't had it for that long, I have shot it a lot. I should have cleaned the internals by now. Lesson learned! Not knowing what caused the leak is going to bother me but at least it's gone for now,

    Thanks for the help guys! Stoti

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    edosan
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    Nice!!, probably was just an o'ring nicked just outside the seal, and in that case is imposible to tell (is was just nicked and not broken)… and is when disassemble and assemble fix the problem. Is important when you assemble back to take extra careful with o'rings as Ernest mention on his videos in order to avoid that.

    Anyway glad there is no leak anymore! 👌

    • This reply was modified 5 months ago by edosan.
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    airgunfans
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    Congrat for fixing the leakage.  The same mystery has occurred on my Air Arms FTP900.  The filling port leaks loudly when it came but after I took it apart and together again, the problem vanished.  I think some foreign debris caught in the valve seat was removed unintentionally in the process.   

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