Air leaking from head - Hitachi NV45AB2 Roofing Coil Nailer

The trigger valve should release air when depressed. This release of air comes from behind the head valve. If the head valve does not pup-up when the trigger is depressed then air is leaking past the head valve orings. Try coating the head valve orings with plenty of white grease and retest. If the gun fires you know that orings are leaking. Test with no more than 100 psi. Good luck with your repair.

If it were the check valve, (safety release valve), you would hear the air escaping from the safety release valve. You have an air leak somewhere. A small leak in the system will keep the compressor from building pressure. If you turn the compressor on and feel around the ends of the tube that leads from the compressor cylinder head to the tank (be careful... it will be HOT) you may feel air escaping from the tube connector at the tank or the connector at the compressor cylinder head. If that is the case, tighten the connectors at the compressor head and the tank. If the connectors still leak, you will need to remove the tube and replace the packings (gaskets) at each end of the tube. Also check all of the hose connectors for leaks, and check the hose for damage that may cause an air leak. If you remove the air hose from the compressor and run the compressor you will be able to tell if your problem is in the hose or hose connectors or the compressor-to-head air tube.

High temperature discharge air is caused by leaking reed valves or leaking head gaskets. Another indication of leaking head parts is that it takes longer to fill than usual or the compressor will not reach cut-out pressure. Good luck

Check all connections for air leak including the water drain valve with soapy water. If no air leaking from connections, spray soapy water on head area where head attaches to the cylinder checking for gasket leaks. If no leaks are found, most likely problem is in the head /valves /internal gasket leak. If head gasket or valves are leaking, you will notice that air seems to blow out of the intake filter (normally there is good suction at the intake). Good luck

Mark:

There is an air leak in the system. check the easy stuff first. let the compressor run, and carefully feel around the ends of the tube that runs from the compressor cylinder head to the tank. You can sometimes feel where the air is escaping. You can also squirt a soapy solution on the ends of the tube and look for bubbles or pressurized air blowing the fluid back in your face :-).
When you find the leak, you will know how to stop it. Also check the drain valve at the bottom of the tank to make sure that it is closed and not leaking. Check your hose connections for leaks... remove the air hose and run the compressor.. if it builds pressure, your hose connections are leaking. The harder stuff... Take the shroud off, check the head bolts for torque and the head gasket to see if it is blown, (Use the soap solution). The really hard stuff... If you have found no leaks, the valve body or piston ring(s) are the problem. You'll need to pull the cylinder head and replace the valve body or piston or piston rings.

Good luck

bad regulaor or thers a leak on the cylinder head . does it take a long time to reach pressure. if at all. sounds like a leak on the head replace diaphram or check and see when you start it if air is leaking around the head.

This problem is caused by air leaking past orings in the head valve. Remove head and pull out the head valve. The metal surface on the head where oring makes contact should be smooth and oring should fit snugly. Of scratched or deep groove, or if oring is worn, the gun will not fire (sand with very fine paper or replace head). Also examine the headvalve where smaller oring makes contact. If small scratches are visible, remove with very fine paper or replace. To test if head valve is the problem, remove head and headvalve and apply plenty of white grease where orings make contact and replace head then test. If the gun fires, air was leaking past the orings. Good luck

Make sure no nails in gun. With air connected listen for leaking thru nose of the gun also. If leaking thru nose slightly, air is getting past the cylinder seal oring and/or top of cyl is not seating against headvalve. Repair leak to nose of gun before trying to fix head leak. With no air leaking thru nose of gun, add plenty of white grease to orings in the head (one oring at a time) to see if leak is less and/or grease will streak behind the leaking oring. Then repair as needed. May need slightly thicker oring or sand surface where oring makes contact to remove scratches that are allowing air to pass. Also air can enter the head thru the small port in the gasket leading to the head (make sure that the gasket is sealing).

If air leaks when motor is off, fault most likely in-tank check valve. Follow discharge air line from pump to tank. Brass/steel valve at tank is the check valve. Remove hose to valve and check for leak. Replace as needed. If air is leaking while motor is running fault could be reed valves in head. Faulty reed valves in head, or torn head gaskets will cause very hot discharge air and tank will most likely never fill to shut off (or take a very long time to fill)

Most all Hitachi nailers that use the plunger style of firing/safety mech will leak air past plunger (part #877-339) when firing, however should not leak when connected to air or resting. If air is leaking past plunger when connnected to air check following:
Remove head to reveal cylinder plate (part#877-318). Remove plate and check outer oring for nicks or broken. If nicked or broken, replace and problem solved. If in good condition, remove cylinder guide (part #877-310) and check two outer orings for nick /cut. Use caution when removing/installing cylinder guide. It is easy to pinch orings when installing causing air leak at plunger. If orings are in good shape then problem is warped body of gun not allowing outer orings to seal. To check for warped body, use the cylinder plate as a guage by lowering it into the area where the cylinder guide rests. Good Luck with your repair.