Troubleshooting Air Leaks On A Pneumatic Tool

Have you ever tried firing a pneumatic nailer, only to hear air leak when pulling the trigger? If so, you're not alone. Over time, wear and tear will take its toll on any air tool, regardless of the brand. The best way to prevent an issue on the job, practice preventative maintenance. Keeping pneumatic tools properly lubricated with air tool oil, as well as cleaning them regularly will help prevent wear. Storing tools in plastic helps to keep dust and other elements out - especially when sitting for extended periods of time.
But what about the unavoidable issues, like an occasional air leak?
If you try to fire a pneumatic nail gun or stapler, but only hear air leaking when engaging the trigger, it's likely that your tool's "O-Ring" is not sealing properly. When the trigger is not depressed, you may not hear air leaking, as the valve is probably sealed. However, once you engage the trigger, the valve looses its seal, therefore creating a gap for the escaping air you hear coming from your air compressor, as it flows into the tool.
On a properly working pneumatic tool, when air is forced into the firing valve, this pushes the valve upward, which opens the main cylinder sleeve and allows the air to drive a fastener. If the "O-Ring" fails to seal, the air will escape, creating your leak.
While this may seem to be a complex repair, don't get rid of your tool just yet - fixing the issue may be easier than you think. Simply stretch the "O-Ring" on the firing valve and apply grease. This should take care of the issue - helping your air tool run properly. Keeping a tool's "O-Ring" lubricated will increase the ring's lifespan, and prevent drying out.
We must note, this is not the only cause for a pneumatic nailer or stapler to leak air, just a common source when troubleshooting a leak.
Always remember to stop using your air-powered tool - or any tool - when it is not functioning properly. Take your tool to a certified repair technician or complete any necessary adjustments yourself, before using the tool again. Failure to take the necessary preventative measures can result in injury, or can lead to further damaging of your tool.
You may want to learn more about choosing the right air compressor for your application. An under-powered compressor can also lead to misfire or weak firing of your pneumatic nailer.
~ The Nail Gun Depot Team
Leave a Reply


  • Sue Jackson November 21, 2016 at 12:09 PM

    Do you sell replacement O rings for the ISM AB100T pneumatic staplers? What kind of "grease" do you recommend?
    We purchased a stapler from you in 2011, so I need to repair or replace now.

    • Nail Gun Depot November 22, 2016 at 7:22 AM

      Sue, I've forwarded your request to our customer service team, who will contact you shortly in regard to options for repair versus replacement. Thanks for contacting Nail Gun Depot!

  • Randy L December 20, 2017 at 5:19 PM

    Hitachi NT65MA2 15-Gauge Angled Finish Nailer
    My gun started hissing air from the head and it had air coming out the exhaust port. It started very light and it got worse and I was working till I had to get another gun hooked up and going.

  • Edward April 10, 2018 at 10:42 AM

    I got a air nailer it leaks air out of the trigger when I hook up the air line to it .. I was wondering why ??

    • Nail Gun Depot April 10, 2018 at 11:21 AM

      It could be an O-Ring not sealing properly, but there are several possible causes. We'd suggest having the tool evaluated by an authorized repair center.

  • Carlos Ordonez July 19, 2018 at 5:46 AM

    My question is can I buy a oil ring for my Central Permitting nail gun thanks Carlos

    • Nail Gun Depot July 19, 2018 at 5:59 AM


      We typically do not get into parts. We suggest contacting the manufacturer. Sorry we couldn't help more this time.

  • Steve Bolin July 29, 2018 at 8:47 PM

    I have a Craftsman 351.184200 and the seal (piston stop) is broken into pieces. The part #7424 is discontinued. Is there another substitute part that might work. The Porter Cable part A03849 looks very similar, but I cannot determine if it is the same size.

    • Nail Gun Depot July 30, 2018 at 5:42 AM

      Hi Steve. Wish we could be more help, but we do not stock either of those brands - and we also do not typically get into parts. If you're interested in a new gun or fasteners, please keep us in mind!

  • gerardo salls September 7, 2018 at 5:29 AM

    Hi< i have the Duo-Fast RCN-60-225. I change the all repair kit because the gun start to thru air on front side where the nail come out. After change all O'ring i assemble back and continues leak on front side. What i cant do to fix that problem. Thank you..

    • Nail Gun Depot September 7, 2018 at 7:09 AM

      It sounds like you will need to take your tool to an authorized repair center for service. It's hard to diagnose air leaks without seeing the tool, as there could be several possible sources for the problem.

  • David Dobbs October 24, 2018 at 7:44 AM

    My DeWalt crown stapler leaks air at the swivel at the back of the gun. Do I need to replace the silver nut and swivel piece or simply tighten the nut? Or is there possibly another issue there?

    • Nail Gun Depot October 24, 2018 at 7:52 AM

      It could be a variety of issues. Without seeing the tool, it's hard to diagnose. We recommend taking the tool to an authorized service center for further troubleshooting.

  • Douglas L Dennison December 1, 2018 at 5:12 PM

    The"O-ring." My nailer/stapler has about 10 o-rings. Can you be more specific?

    • Nail Gun Depot December 3, 2018 at 5:44 AM

      Hi Doug,

      Great question. Every nail gun is built differently depending on brand and model, which makes it hard to diagnose a particular tool without seeing it. These tips are to help get you started, but we always recommend taking your tool to an authorized service center for troubleshooting.

  • Carlos Suarez February 9, 2019 at 3:13 PM

    Bostitch n66c shoots a nail as soon as air is hooked up to it, then jam. Does it have to do with the trigger assembly?

    • Nail Gal February 11, 2019 at 4:42 AM

      Hi Carlos,

      Unfortunately, it's hard to diagnose a tool over a blog. We recommend taking the tool to a local service center, or shipping it to our location for a technician to diagnose.

  • Cliff G. April 23, 2019 at 3:30 AM

    I have a Porter Cable Framing Gun, owned several in the past, no problems. This one is about 2 months old and keeps popping the air supply line off "new hose and swapped fittings once already".

    PSI set at 100 off tank


    • Nail Gun Depot April 23, 2019 at 6:34 AM

      Hi Cliff, we recommend taking the tool to an authorized Porter Cable servicing center.

  • Gilbert Koros June 1, 2019 at 12:04 AM

    Hi, my jn80c pallet coil nailer keeps on jamming and when I checked it I realized bumper wears on top on its peripheral and debrises preventing the next round of nail to be hammered,what could be the issue?

    • Nail Gun Depot June 4, 2019 at 6:54 AM

      Hi Gilbert. Bumpers are a normal wearing part and do need to be replaced occasionally. If debris breaks off and covers or clogs the air supply hole in the nose for your feeder piston, you would definitely have jamming/skipping issues.

  • dennis June 19, 2019 at 6:30 PM

    I have a senco stapler that leaks a lot from top of gun without pressing trigger

    • Nail Gun Depot June 20, 2019 at 7:12 AM

      Hi Dennis,

      It sounds like the problem is a worn head gasket or O-ring. Our on-site repair pro responded that, "No tool should leak air in the static (unfired) position." We recommend taking it to a local service center, or shipping it to us for service. Please contact Customer Service if you prefer to send it to us.

  • Peter Messinger July 10, 2019 at 5:44 AM

    I have a master fastener finish nailer which needs to have the orings replaced after many good years of use. Master no longer supplies replacement parts. I have the parts list but am unable to match up the replacement orings. Can you help?

    • Nail Gun Depot July 10, 2019 at 7:29 AM

      Peter, please give us a call at 1.888.720.7892 and we'll do what we can to help. We don't typically get into parts, unless the tool was purchased through us, but we may have something comparable available.

  • Vincent Durante September 19, 2019 at 2:23 AM

    I have a SENCO SLS18 staple gun that wont fire. When I first pull the tigger air runs out of the vent at the back of the gun where the air connection is. I could use a little help. Is it just just seals or do I have a bigger problem. This staple gun isn't even a year old and should not have this problem.

    • Nail Gun Depot September 19, 2019 at 5:50 AM

      It could be a variety of things, but most likely is in need of o-rings being replaced. Based on the tool's age, we'd suggest taking it to an authorized service center to confirm it's nothing more serious. If the tool is under one-year old, it should still have a manufacturer's warranty on non-wearable parts (unfortunately o-rings are considered wearable). Please let us know if we can further assist.

  • Tom September 24, 2019 at 1:30 PM

    RE: Bostitch N55 (may be a N55C) Siding Coil Nail Gun: Gun has lots of use, but worked until a few roofing nails were run through it. I freed the jam and debris and then found the following:

    When TRIGGER PULL: Piston drives full stroke and then: 1) does not retract, 2) big constant air discharge out the top port Additional trigger pulls do nothing.

    DISCONNECT AIR: Piston can be manually pushed back w/o issue. In some cases, the feed piston is mid-stroke.

    DISASSEMBLY: The piston/cylinder look OK as does the head assembly. All parts move freely and no visible bad O-rings. I'm going to pop out the Trigger Valve and inspect

    TROUBLESHOOTING QUESTION: How does this gun operate? 1) What happens when you PULL & HOLD trigger and then what happens when you RELEASE trigger? (Do you need to release the trigger for the piston to reset?)

    Thanks so much!
    Any help will be greatly appreciated.


    • Nail Gun Depot September 25, 2019 at 8:29 AM

      Our service technician believes the issue is tied to your head valve. Unfortunately, parts for your tool are almost impossible to locate.

      To answer your question though, when you pull and hold the trigger, it resets.

      We'd suggest replacing with a new tool. We offer a Freeman unit priced today at $179, or have the replacement Bostitch tool (N66C-1) for $249.

      Please let us know if we can help in any other way.

  • James H Whitaker October 30, 2019 at 7:09 AM

    Thanks. This nail gun is straight out of the box, Craftsman. I will exchange for another. Leaking air from the trigger.

    • Nail Gun Depot November 1, 2019 at 6:06 AM

      Glad this article was useful. Please let us know if you need any fasteners for your new nailer. We'd be happy to help!

  • Bill D November 17, 2019 at 7:08 PM

    I have a Senco Framing nailer that has sat on my shelf for a couple of years with no use. Tried to use it today, but it leaked air each time I pulled the trigger. I would like to tried your solution you suggest above in the article. My question is, how exactly do I stretch the "O-Ring" on the firing valve and apply grease. Can you point to some specific step by step instructions. I would like to try this before I tear the nailer down.

    • Nail Gun Depot November 18, 2019 at 7:16 AM

      Unfortunately, to get to the firing valve, you'll have to tear the nailer down anyway. But, once you reach it, you should be able to pinch the O-Ring with your fingers to stretch and apply grease. While we don't offer specific step-by-step instructions here, our Service Manager indicated there are several videos floating around online that may help. You can also contact the manufacturer at 800-543-4596.

  • Benjamin Jackson February 25, 2020 at 5:59 AM

    I have a FramePro 600, FRH. Air leaks when attached to the compressor. When the trigger is pulled the leak increases. Gun does not discharge.

    • Nail Gun Depot February 26, 2020 at 5:27 AM

      Hopefully, a new set of o-rings can fix the issue. The tool really needs to be looked at by an authorized service center to properly diagnose though.

  • charli March 24, 2020 at 9:51 AM

    when to nail air coming out on levr

    • Nail Gun Depot March 24, 2020 at 12:12 PM

      Sounds like it's time for service!

  • Ken March 24, 2020 at 9:54 PM

    I have a cable porter 350 that needs a gasket that is obsolete. Can I use a liquid gasket to make the seal?

    • Nail Gun Depot March 25, 2020 at 11:12 AM

      We wouldn't recommend using liquid gasket, as it might ruin the tool. We don't sell Porter Cable, but you may be able to source a new old stock part for your tool online. There are also several budget friendly tools on our site, so it may be more cost efficient to simply upgrade to a new tool.

  • Donald Shott March 30, 2020 at 10:22 AM

    I have a Senco SCN65 that was leaking air out of the top air vents. I replaced all O rings and it worked fine for a day. the next day it blew air back out of the vents again so I took it back apart cleaned it, checked all the O rings, reassembled it and it worked for a day. The next day it no longer worked, I re-cleaned, checked everything but this time it did not work. I have also replaced the CF0015 exhaust valve and BB0186 exhaust firing valve assembly and new O rings. I have also replaced CA0087 Lower Remote Assembly Kit.
    However, the unit still does not work and blows air out of the top air vents. Do you have any suggestions or solutions?

    • Nail Gun Depot March 31, 2020 at 8:31 AM

      While it is hooked up to air, carefully feel under the nose. If there is an air leak out the cap and out of the nose, you should replace the sleeve seals. Also, while unhooked to air, remove the exhaust deflector. Make sure there are no cracks in the cap.

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