Grex p635 leaking air when I hook up pinner it doesn't pin triggrr just leaks air

Typically the problem is one of 2 things:
1) You have a broken or chipped driver blade - this is the most common especially in pinners - the tiny tip on the driver breaks off.
2) The bumper underneath the piston is broken keeping the piston from going all the way down (Less common)

You have an "O" ring seal leaking is my guess, take it apart and replace all the seals, any Auto parts store that is full service (not Autozone) will have an assortment of "O" rings so you can match them up. Use Silicone grease when installing the seals.

Easy test, remove the trigger to expose the firing pin and remove the nails. With air connected very quickly depress the firing pin all the way in. If the gun fires, the safey foot is not pushing the pin all the way in. Make adjustments to correct. If the gun still does not fire, the headvalve orings are leaking internally. Remove the head and pull out the head valve. Make sure that there are no fine scratches on the surface where the headvalve orings make contact to cylinder in head. If scratched, remove with very fine sandpaper. Remove the large outer headvalve orings and wind a couple of turns of teflon tape in the groove and replace the oring. This will make the oring fit more snuggly against the head. Lube with white grease and test. Good luck

An Oring needs to be replaced... if the driver stays forward its usually in the trigger assembly

make sure nails are not being put in backwards, your driver may be worn or broken

By all reports, this is an excellent pinner.

This is an excellent product. When used it at 90 psi with the 1 3/8" pins there should be no issues with putting pins through shoe molding, corner molding, pinning crown miters, etc.

NOTE: The specially designed nail channel is designed to prevent jamming

However, there is a minor that I've experienced: it is difficult to load a new clip of pins when there are a few still left on the old clip. The spring mechanism pushes the two clips together pretty hard when you close the magazine, and the ends of the clips can get doubled up, jamming the magazine.

I don't know of any fix for this problem, so I recommend that you only refill it when it is completely empty.

If you've never used a pinner before, you should keep in mind that it is NOT going to replace your finish nailer.

I trust that this was helpful.

How often do you add oil to the nail gun? Add a couple of drops of air tool oil where you hook on the air hose. Your seals are probably dry,allowing air to escape past the o-rings. If that doesn't work you'll have to get a rebuild kit from your dealer or order it on line and replace your o-rings.

driver is either bent/burred or you have a pin double fed. Or does it make a hissing noise after you fire it?

If you need further help, I’m available over the phone at https://www.6ya.com/expert/matt_8dbc24bf722649ac

This problem can happen because of several reasons.
Most likely the driver stuck, and not able to move.

First with the tool disconnected from the air supply check to see if there any nails jammed in the nose piece.

If the driver is stuck down, try to push it up. Will it move?

If there are no problems visible at this point you will have to open the tool up, and see if anything looks out of place.

To examine the inside of the tool, unscrew the 4 bolts on the cap of the tool. Gently remove the cap, it may be spring loaded but once the bolts are loosened, there is no reason to be afraid of the parts springing out. Be careful not to let the parts that are in the head cap fall out. Also take care not to rip the gasket. Keep in mind, the less parts inside that you disturb the better so be careful.

If the piston driver does move. Does it move freely?

Sometimes when a driver hits a very hard knot in the wood, or if a nail is hit. The thin driver may bend. If it is moving but with resistance. Use a thin object to push the driver upward from the nose. It will come out of the head cap end.

Check to see if the driver is straight and square to the piston. If it is bent, you may need to replace it. Sometimes you may be able to bend it back enough to allow the piston driver to move freely.

If this solves your problem. To reassemble:

Replace the driver in the correct position. Replace the gasket if it is loose. If parts came out of the head cap, reposition them into the cap. Replace the head cap on to the tool. Replace the bolts, stagger as you tighten them to depress spring loaded parts evenly.

Hook the tool up to your air supply check for air leaks, and fire the tool.


If the driver does not move: Examine to see what is seizing the piston and reply back.

I hope this works!

The blowing of air into the coolant resevour is caused by a leaking head gasket. What's happening is the cylinder is blowing air into the cooling system causing this to happen.