# Dewalt Framing Nailer leaking from Cap & Exhaust deflector



## seanbooks (Jul 10, 2017)

Hello,
I have a Dewalt D51825 Framing Nailer. It was leaking from the nozzle, so I replaced 2 o-rings that were badly worn out on the cylinder. (Parts #50 & #51 from ereplacementparts dot com) Schematic is located there if you search for Dewalt D51825, but I can't post a link because I am a new user.
Now that I have re-assembled it, it is now leaking from the top of the cap, from under the exhaust deflector. (Part numbers 3 & 13.)
Any ideas? It wasn't leaking from there before I took it apart, so obviously I messed up somewhere. 
Thank you, 
Sean


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## chandler48 (Jun 5, 2017)

I have found that replacing one or two rings, places undue pressure on other rings of the same age and they fail. It is always best to buy a complete rebuild o ring kit and do them all. Ereplacementparts is a good source, although quite expensive since they only sell individual parts. I try to locate the entire kit on sites such as Ebay or googling the brand/model to locate the kits.


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## seanbooks (Jul 10, 2017)

I did buy the complete o-ring replacement package from Dewalt here in Canada. (I cited ereplacementparts to show the schematic with part numbers.)
The two I replaced were the yellowish ones. The rest of them were the black ones and they all looked good, but I did replace 2 other black ones that looked slightly questionable. 
I don't think it's the other o-rings, but if it was, which one(s) would allow the air to bleed out the exhaust deflector? Most of the others seem to allow leakage around the trigger or nose. 
Thanks, Sean


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## chandler48 (Jun 5, 2017)

If you aren't going to replace them all as suggested, put 3 drops of tool oil in the air inlet and cycle it a few times.


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## seanbooks (Jul 10, 2017)

I finally did a detailed inspection on the whole tool and found that when I re-assembled it I had damaged another o-ring. Replaced the damaged o-ring and it works like a charm! 
:smile:






seanbooks said:


> I did buy the complete o-ring replacement package from Dewalt here in Canada. (I cited ereplacementparts to show the schematic with part numbers.)
> The two I replaced were the yellowish ones. The rest of them were the black ones and they all looked good, but I did replace 2 other black ones that looked slightly questionable.
> I don't think it's the other o-rings, but if it was, which one(s) would allow the air to bleed out the exhaust deflector? Most of the others seem to allow leakage around the trigger or nose.
> Thanks, Sean


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## tandev (May 3, 2018)

hey, 

I have the same problem with the same D51825 nailer. 
initially it has developed a leak from the trigger valve, so I went ahead and purchased the complete set of o-rings for the valve and the cylinder. 
I regret I touched the cylinder though, cuz now it won't stop leaking from the exhaust. Exactly like @seanbooks described above. 

Since then I purchased a set of original o-rings from Dewalt service centre, hoping it will help. When I put everything together the nailer fires fine for some time, but after I let it sit for an hour or so it gradually looses power and eventually develops this nasty leak from exhaust..

Any clues at which specific o-rings I should look? 
I have inspected everything few times now and did not find any visual damage...

Thank you so much


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## chandler48 (Jun 5, 2017)

Did you change all the o rings and lubricate them as you reassembled it?


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## tandev (May 3, 2018)

I did change all orings and did lubricate them with silicone grease. 

I kept researching it online for a while and came across this


_V)	Symptom:	Won’t Actuate – Continuous leak from the exhaust with the contact trip depressed and
trigger pulled._​
_1)	Something is keeping the cylinder from sealing against the cap. _​
could it be the cylinder spring needs to be replaced?
or perhaps any other seal (except the orings)?
does it need to be any movement of the cylinder for it to fire properly?

Like said, nothing is visually broken or heavily worn but maybe anyone has similar experience before?


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## tandev (May 3, 2018)

what is weird is that the nailer works immediately after I assemble it, and it keeps working for hours unless I leave it sitting on the bench for any longer than 30 minutes.
After being half hour idle it drives the first nail half way, and then keeps working like normal again. But if I leave it idle for longer, it won't drive any nail and will just keep hissing from the top with trigger depressed. 
If trigger is not depressed there is no leak. 

Does not sound like an O-ring problem to me, or else why would it be working at all?


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## chandler48 (Jun 5, 2017)

Nail guns by nature are not meant to be under pressure for hours without use. You are putting 90 psi against all those o rings and seals and sometimes they leak. I release the air hose from the gun when I no longer am going to use it for a time (10 minutes or so).


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## tandev (May 3, 2018)

Sure thing I do disconnect the air house while not using the nailer, sorry if I forgot to mention that.

The issue is now resolved.
Here is what was the problem, hopefully it will be of use for someone.

I spent hours looking at all nailer parts while assembling and disassembling it until I found this.
So when I installed the ebay O-ring kit I did not pay attention that the oring which seals the cylinder to the bulkhead (the black plastic piece between the cylinder and the nailer body) is somewhat beefier and thicker than the original. I though the original just extended and worn out, but I was wrong. Apparently the new o-ring caused the cylinder sease and not allow the air in when trigger is depressed. Hence the air found its way out through the exhaust instead of moving the piston...
Ironically this part was the only one missing at DeWalt dealership, so I left the ebay one in (it was still new so why not lol!) when replacing the o-rings the second time.

After I put in the original o-ring back where it was, the nailer is working as new. 

Lessons learned: never try to fix something which is not broken. 
Lesson #2: stick to original parts when possible and not something fishy from ebay 

Really hope this will save time for someone else having similar problem.


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## lothian (Feb 8, 2013)

I have the D51844 (type 1) that was blowing air out of the exhaust when the trigger is depressed. I fixed that problem by replacing #6 and ##10 o-rings, but now I have a new problem: I get a quick "pop" sound with each trigger press with no blow-by. (My Bostitch nailers sometimes do this exact thing and the problem is always the piston driver gets stuck. But I have no idea how to t'shoot the piston driver on this D51844.)

Any idea which seal might be the problem?


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## chandler48 (Jun 5, 2017)

I have a Senco framer (21 degree) and three Bostitch F28WW framers that we use. One is always in the shop for repairs. From the diagram you furnished, they are all basically the same design.  I am having your same problem with one of the F28WW nailers. Pull the trigger, it pops, but nothing happens. I may go down today and see about putting it back together and check for piston problems.


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## lothian (Feb 8, 2013)

chandler48 said:


> _...same problem with one of_ [my Bostitch] _F28WW nailers. Pull the trigger, it pops, but nothing happens._


Agreed: The internals of the F28WW and D51844 are very similar. A theory-of-operation document for these tools that illustrates valve-actuation-airflow would be immensely helpful, but I've been unsuccessful locating such online.

I suggest you confirm max supply air pressure at the tool before you begin disassembling it. Dial up the pressure regulator to the max for the F28WW--likely 120psi--load it and test fire.


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## steves7839 (Aug 18, 2019)

lothian said:


> Agreed: The internals of the F28WW and D51844 are very similar. A theory-of-operation document for these tools that illustrates valve-actuation-airflow would be immensely helpful, but I've been unsuccessful locating such online.


On youtube there is an animated tutorial showing the sequence of events as the nailer actuates.
I watched it a week ago, know it is out there somewhere. Will post the link if I find it.

This link is a Bosch commercial, but it will have to suffice for now:


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