I had this rebuilt by a shop, then put a kit in it myself after it fired one brad and re-leaked. I only opened the head portion, not the handle section.
The leak is through the small hole in the head and only occurs when the trigger is not pulled, plus the gun does not fire. The plastic trigger does not appear bent and the gun has only seen light home use.
The new small O-ring seems to bind, unlike the old one and none of the old rings or seals seemed to be worn or leaking.
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Re: Bostitch T31 air leak thru small head hole
I have repaired hundreds of nailers, however not a t31. I can offer you a few tips on general nail gun repair pertaining to leaks. It is important to check each oringseparately if you can to check for proper fit/contact. Do not just replace all orings and then hope for the best. Each oring must fit snugly not too tight not too loose. The surface where the oring contacts must not have fine scratches. Inspect all surfaces with magnify lens for scratches and remove with fine sandpaper. Check each oring for nicks Make sure that gaskets do not block small ports that direct air to headalve. Use silicone grease instead of oil on orings and metal/plastic parts. Lowes sells a small container of silicone grease in the plumbing department. It is used to lube faucet parts. Oil will wash away too fast and sometimes it will swell the orings causing gun to jamb. Finally do not use too much pressure on small nailguns. Try using 70 to 90 lbs. Good luck
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Most likely problem is the head valve orings not making perfect seal. Remove the head and pull out the headvalve piston. Apply plenty of white grease to orings and test fire. If gun fires, will need oring kit soon. Good luck
Most likely the orings or seals in the headvalve are not making perfect seal. Remove the head and pull out the headvalve. Apply plenty of white grease to orings and test again. If the gun fires, then will need oring kit soon, or just keep using plenty of grease. If the gun still does not fire, check that the safety foot is depressing the trigger valve all the way in. Good luck
I had the exact same problem after doing a complete rebuild. If you are using the Stanley bostitch rebuild kit, check to see if you accidently swapped o-rings 6 and 63. They look the same but o-ring #6 is 1.925x.103 and o-ring #63 is 1.862x.103. Use plenty of lubricant. Hope this helps.
If the new trigger valve leaks air when you connect the air supply, most likely defective valve or air is leaking past outer trigger valve orings due to debris in the slot or new orings were cut when the valve was pushed in. If air leaks when you depress safety to fire gun then most likely problem is in the head valve or safety foot is not pushing the firing pin all the way in. Easy test, remove nails and remove the trigger to expose the firing pin. Connect air and very quickly depress the firing pin all the way in. If the gun fires, adjust the safety foot as needed. If the gun does not fire, remove the head and check headvalve orings for good snug fit against the cylinder within the head. The surface were orings make contact must be very smooth and not too deeply worn. If you notice fine scratches remove with fine sandpaper. Reinstall head using plenty of white grease on all the orings within the head and retest. Good luck
Easy test, Remove the nails and remove the trigger retainer pin and trigger to expose the trigger valve (tva6 valve). With air connected and nails removed, quickly depress the trigger firing pin all the way in. Gun should fire (if gun fires, adjust safety foot to make better contact with tva6), if no joy air is leaking past orings in the head valve or head gasket vent hole and/or trigger valve. Remove head and check gasket around vent hold (small hole in the head gasket). If the gasket good remove head valve and examine surface where orings make contact for fine scratches. If scratched or worn, orings are not sealing. To check if orings are leaking, apply lots of white grease to orings in the head valve, replace the head and test fire. If the gun fires, sand contact areas with fine sandpaper and or use oversize orings or wind teflon tape under the external orings. The metal ring or washer that you are wondering about is sometimes used to space up the bumper to control depth of nail. Other nailers use a metal fitting under the bumper to help guide the driver and to seal the lower chamber helping to prevent too much air leaking past the driver. If too much air leaks past the driver, guide, the piston may not return to top. Good luck
The check seal is what causes the piston to retract. Remove cylinder and examine check seal. It is a small band that covers a series of holes and should fit snuggly around cylinder. Other factors that have effect on piston retraction are, split/cracked cylinder, bent driver and lack of lubrication. This gun is tricky to rebuild. Make shure that all the parts in the head are placed correctly. The kit does contain all the parts that you need. Good luck
I have seen many small bostitch guns all with different problems that did not shoot nails. Both of your guns have simillar triggers. You might try the trigger valve from the gun that works to see if that is the problem. Most no fire situations come from faulty trigger valve. The trigger valve used in your guns has a part that stays in the body of the gun; be sure to replace both parts. If still no fire check the following:
Remove the head and check if the piston/driver travels all the way down the cylinder with the tip of be blade showing at the nose. Some piston/drivers have a grove that must be aligned.
Check that the headvalve travels into the head and returns. Push the valve in with your thumb then cover the small vent hole at the base of the head where the gasket sits with your finger and release your thumb. The headvalve should be held in with vacuum then pop up when you remove your finger from the vent hole. If the headvalve does not stay pushed in with the vent covered, the orings are leaking and can cause the gun not to fire. Try lubing the headvalve with light grease such as silicone lube. Do not use bearing grease. Silicone lube is available in small amounts at plumbing supply/lumber outlets such as Lowes. It looks like wax feels like shortening.
Reassemble the gun and check your work. I test the gun with-out nails and without the trigger installed. Just place the nose of the gun on a piece of rubber, (I use a piece of heavy garden hose rolled up tightly into a coil) and press the trigger valve pin with your finger. The reason that I leave the trigger off is that sometimes the problem is caused by the safety mech not pushing the trigger pin correctly. enjoy