Question about Hitachi NV45AB2 Roofing Coil Nailer

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Hitachi nv45ab2 is leaking out the back orings look good 1 year old

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  • philip dieckhoner Jan 03, 2013

    the gun is a year old looks new inside used every day just started one day lube up nice always o rings look brand new



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  • Hitachi Master
  • 1,388 Answers

Remove the head and check that the cylinder moves down and then up again. If the cylinder is stuck stuck down, remove outer ring and pull out the cylinder. Check for grit and or scratches where the orings make contact. If scratched, remove with fine sandpaper, lube and reinstall. Check that the cylinder is in the upper position before you install the head. If the cylinder moves down then up again, check headvalve seal (rubber seal in the head) for cracks or the rubber has become loose and spins. If loose reseal with RTV. If cracked, replace with generic or factory part. Good luck

Posted on Jan 31, 2013


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Posted on Jan 02, 2017

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SOURCE: I want to buy a head rebuild kit, for Hitachi coil

I buy most of my parts from The headvalve is the only part that wears in the head. It will leak when the rubber/vinyl seat material begins to crack(new models use rubber). If the head valve looks ok with no cracks then no problem in head. If you are having problems with the gun please post again describing issue. Good luck

Posted on Oct 16, 2010

  • 109 Answers

SOURCE: Year of Manfacture for Hitachi NV45AB2 Coil Nailer

on hitachi air nailers the first number is the month and the second is the year , the only confusion might be if the nailer is older than ten yrs( the nv45ab2 has only been out about 4 yrs) so your roofer was made in march of 04

Posted on Dec 03, 2009

  • 2176 Answers

SOURCE: On a Hitachi NV45AB2 How do you get the trigger

UNPLUG the tool. on the trigger itself you will find a roll pin, remove it then with the trigger off you will see what appears to be a slot for a straight screwdriver, you can lay a screwdriver blade the width of the slot and turn to loosen and remove, next on the front there is a spacer with o rings on it carefully remove it and the spring can be removed. If you go to " you can download a schematic for this. On the left side click on the Hitachi parts and go to nailers and scroll down till you find your model is is on the left side of the mini page click on it and you can see the schematic. Let me know if you need more help

Posted on Feb 27, 2011

  • 2176 Answers

SOURCE: Need manual for Hitachi NV45AB2

go to "" and you can download the manual you are looking for. Let me know if you have trouble or need more assistance.

Posted on May 07, 2011

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1 Answer

Hitachi 45ab blowing air out of trigger

If air leaks thru trigger as soon as you connect airline, replace the vinyl ball under the trigger stem. If air leaks when you depress the trigger, replace the small oring on the trigger stem. If air leaks slightly from plunger in front of the trigger valve, problem is inside of the gun. Remove the head and pull the large circular plate. Replace the large outer oring. Good luck

Feb 10, 2014 | Hitachi NV45AB2 Roofing Coil Nailer

1 Answer

Blowing air out of trigger

Leaking under trigger could be the ball seal part # 875645 if leak starts as soon as you connect the air hose. If no air leaks when you connect hose but begins to leak when you depress the trigger then replace the oring on the plunger which is part # 874820. If air leaks when you connect the hose and the ball mentioned above is good then most likely is leaking from oring # 876161 installed on cylinder plate (remove head and pull out the plate). Good luck.

Feb 10, 2014 | Hitachi NV45AB2 Roofing Coil Nailer

1 Answer

Skiping nails

Usually caused by weak feeder spring, however if new spring does not fix problem then check or replace orings on the feed piston (3 orings) , replace the driver oring and make sure that the driver sheet seal is not broken. The sheet is located at the very bottom of the inside of the cylinder area. If good, the driver will not pull out of the gun from the top of cylinder. To see the condition of the sheet, gently pull up on the driver just enough to look down the cylinder past the bumper. If the sheet is missing a piece, air leaks past the driver and does not push the driver all the way back up to top of cylinder causing miss-fire. Good luck

Sep 09, 2013 | Hitachi NV45AB2S Coil Roofing Nailer

1 Answer

How do you remove cylinder guide hitachi nv45ab2 roofing coil nailer

Cylinder guide fits very snuggly into cylinder and generally does not need to be removed unless visually broken. If you have a leak and suspect the orings under the guide, re-post a question. If however you want to pull anyway, I use one arm of a large two arm puller. Remove the outer ring, pull out the cylinder, then gently tap the under side of the guide with the lip of the single arm. Move the arm from one side to the other and it will come right out. Second method is to remove lower half of the gun and push out with rod or hardwood dowel. I have remove many by tapping up with lip of puller and have not damaged any. This part is quite strong, however have not ever needed to replace the orings under this part. Good luck

Nov 24, 2012 | Hitachi NV45AB2 Roofing Coil Nailer

1 Answer

My hitachi roofing gun leaks air from trigger when not pressed

Two areas to check when air leaks from around the trigger. Rubber ball under trigger pin will cause air to leak, however when good side of the ball falls on the seat, air will not leak for a while. If air is leaking from plunger pin (just in fromt of the trigger pin), remove the head and pull out the cylinder plate to reveal broken oring (oring part # 876161). Good luck with your repair project.

Jun 05, 2012 | Hitachi NV45AB2 Roofing Coil Nailer

1 Answer

Leak air for the trigger

Could be leaking from trigger or in front of trigger at plunger. Spray soapy water on area and determing exact leak. If from trigger pin, remove pin holding metal trigger (3mm roll pin) and check white plastic plunger for oring on groove. If oring is in place then check vinyl ball inside trigger valve bushing. Replace as needed. If leak is in front of trigger at black boot, remove head and replace oring on outer part of cylinder plate (donut shaped plate at top). Good luck

Mar 01, 2011 | Hitachi NV45AB2 Roofing Coil Nailer

1 Answer

When I take the trigger apart and then put it back in the same way it then leaks air. I have 4 guns and I have been carefully cleaning them. Each time I take the trigger parts out and clean them and...

I believe that the most popular roofing gun for professionals is the hitachi line of nailers. Hitachi guns are amoung the very few however that actually move the cylinder when fired instead of the headvalve. This is rather odd because it requires more moving parts. Your guns have a trigger pin/plunger (white plastic with small oring part # 878-121) that pushes on a urethane ball. This ball is potential cause of leaks. Make sure that the ball is perfect. Replace as needed. Most leaks around the trigger area are acutally coming from just in front of trigger which is plunger pushed by safety foot. Spray soapy water around trigger area and make sure where air is actually leaking. If leaking from safety foot plunder source of leak is actually orings inside of gun around cylinder. (usually oring part #876-161 that fits on the cylinder plate). Parts and parts lists are at Good luck with your guns and post again if you have other question.

Jul 29, 2010 | Hitachi NV45AB2 Roofing Coil Nailer

1 Answer

Air is coming out by the trigger and causing it not to drive nails. The air only comes out when the trigger is compressed. How do I fix this?

Remove the trigger by removing the roll pin and check that there is an oring installed on the trigger plunger. The plunger is a white plastic part and requires a small oring about 1/4 " in size. You can buy orings at Lowes Lumber in the plumbing department, about one dollar for package of ten. That should take care of leak when trigger is depressed. Good luck and post again if you need more help.

Jun 16, 2010 | Hitachi NV45AB2 Roofing Coil Nailer

1 Answer

My nailer leaks air out the back my,roofing nailer wont hold any air

Hitachi nailers are built on very close tolerences. Dirt /grit will prevent cylinder from resetting causing air to leak out of top of gun. You can force a reset by striking the gun head first against a rubber mat. Only one or two hits because you could damage the head. If the gun does not reset you will have to take apart and clean out grit and replace orings as needed. Good Luck and post again if you have other questions.

Mar 10, 2010 | Hitachi NV45AB2 Roofing Coil Nailer

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