There's nothing much BUT o rings that can fail, except for the recoil piece in the head. Buy a rebuild kit and replace all the o rings, one at a time and replace the trigger assembly as well. I can't tell where your hissing is coming from, but the repair kit should solve it.

I see you have already read the thread : https://www.diychatroom.com/threads...threads/hitachi-nv65ah-trigger-valve-issue.763144/?post_id=7299197#post-7299197

 

Thanks for quick response. I ordered O-ring kit. You mentioned "replace the trigger assembly" ... is that a part or is that also an o-ring upgrade? I see that the O-ring kit has o-rings for the trigger as well as the piston assembly. I think the trigger is where my leak is.

All seems doable, if done methodically. My biggest concern is disassembly can sometimes be an arcane science (need to know which screw, which clip, which pin, etc needs to be removed).

Will give it a go. Thanks again.

 

I find it easier to pull the old trigger and put in a new one rather than fuss with the small rings in it.

Yeah, the o ring package will have a scale diagram of all the o rings, so you lay out the new rings on this paper and use them one at a time to replace the bad, or used ones. A large flat clean table top in the shop is always best to do the tear down on.

 

I like the idea of replacing the trigger valve entirely but have no idea where I can purchase the assembly. Any suggestions on where to look? I did a little more experimenting with the gun and am pretty convinced that the leak is in the trigger valve ... air seems to be leaking around the trigger when I activate it.

 

I didn't find one a ereplacementparts.com, but this one may fit. Pull yours and compare the components.

Goodnailer NVH45 Trigger Valve Set fits Hitachi NV45AB2 Roofing nailer aftermarket parts - Amazon.com

Goodnailer NVH45 Trigger Valve Set fits Hitachi NV45AB2 Roofing nailer aftermarket parts - Amazon.com

www.amazon.com

 

Thanks for the research. That particular part is not compatible with the NV65AH nailer. A very different configuration ... but at least it got me motivated to start disassembly The o-rings on the trigger valve seem very accessible ... is it just the small size that makes them difficult to replace? I suppose they don't stretch much, like the bigger rings will do.

 

The O-ring rehab has the gun back in operation. Thanks for the support. Video on YouTube was helpful: Hitachi nv65ah Nailer Rebuild? - YouTube.

 

Glad you got it back into service. Mine is still a problem child parts tool with worn-out body.