Snap-On MG325 airgun problem.

[g-tuned]

Hi new to this forum, have this Snap On Mg325 3/8 air gun and it is not working as it should. The reverse seems to have some power whilst the forward torque to tighten is very weak, I have opened the gun installed new oil in the hammers but it still shows same symptoms.

The forward torque is weak enough for me to stop it by hand. There seems to be a leak coming from the direction and torque valve, I installed new orings there but same problem.

How do these guns actually operate, I see the vanes must get driven by the air pressure, so if they are not sealing there is no power? But how come reverse has more power?

Are the vanes meant to be dry ie no oil lubricating them? The gun has an enclosed oil system for the anvils. I dont really have much experience and knowledge on how each component actually work.
I may open it back up and take pics....

 

[Skyline]

First of all, the schematics are on-line on Snap-on's web site, and you can easily order any part. If the part you need does not seem to be there, call, they can probably find an equivalent. Second, before you tear it down again, spray lightweight oil (WD30) in and run it; then repeat this a few times. If the speed increases, it's possible its gummed up due to the oil inside getting too old, or from disuse, or simply too heavy oil used. Please note that due to it's light weight, the WD30 is likely to make quite a mess out the exhaust. Run the gun for a bit to get most out. If that works, follow up with a few drops of Snap-on air tool oil. Run the tool until it's not making a mess any more.

If that doesn't work, there could be a bad seal, a bad vane, or a bad trigger valve. You need to then take the thing apart and examine everything. Make sure none of the metal parts are damaged. The vanes must move freely. You should order every rubber part in the gun, including the trigger valve, and the back gasket. Clean everything and then rebuild. It will cost a third or less than sending it to Snap-on for the same rebuilding service. If one of the major components is damaged, the gun is toast; the shell or barrel costs more than a working used gun. I have had great success rebuilding Snap-on guns and other air tools. IMO, their excellent web site and parts availability makes them ALWAYS worth rebuilding. It is not rocket science; especially when you print out the exploded view and keep it in front of you. I wish other brands did this. To me, this feature alone makes Snap-on air tools much more valuable than competitors to own long term, (they tend to be work pretty good as well).

One other thing...you got enough CFM??? I had an older Snap-on IM31 that barely worked until I switched to a higher volume Milton V type fitting. Gun worked great after that...it simply was not getting enough air. (I have only a 5hp 120v compressor).

 

[g-tuned]

Thanks for the reply.

I did open it already, tore it down and degreased all parts and cleaned dry. Installed the anvil and hammers, filled with 0-30w engine oil, I could not tell if the vanes/blades were worn or not, the cylinder inside where the vanes run looked 'ok'.

If the vanes are toast how come they have more power on reverse than forward movement? I think lack of power and getting stuck has to be vane related issue.

CFM wise I have it set to 90 psi, my bluepoint 3/8 works fine, it is a belt driven 4hp compressor.

 

[devoncoolman]

Send it to snap-on they have a flat rate repair program for all their air tools. Its $125. Good deal. Way cheaper than buying it new. The vains are probably toast.

 

[franzdom]

Am I supposed to be oiling my MG325? I haven't so far and thought it was time to start doing so but it looks like it's a sealed system, please confirm thanks!

 

[Fcvapor05]

Am I supposed to be oiling my MG325? I haven't so far and thought it was time to start doing so but it looks like it's a sealed system, please confirm thanks!

You don't need to oil the anvils, they are sealed; you should add air tool oil frequently if your shop air source isn't oiled already.

 

[Fcvapor05]

Thanks for the reply.

I did open it already, tore it down and degreased all parts and cleaned dry. Installed the anvil and hammers, filled with 0-30w engine oil, I could not tell if the vanes/blades were worn or not, the cylinder inside where the vanes run looked 'ok'.

If the vanes are toast how come they have more power on reverse than forward movement? I think lack of power and getting stuck has to be vane related issue.

CFM wise I have it set to 90 psi, my bluepoint 3/8 works fine, it is a belt driven 4hp compressor.

Pressure /= CFM. Does the compressor start running as soon as you start using the gun? It needs 90 psi or so at the end of the hose, not inside the tank. Pressure drop through the hose, restrictive fittings, compressor too small... any of the above could fix the issue if the gun is OK.

 

[DodgeMech]

Am I supposed to be oiling my MG325? I haven't so far and thought it was time to start doing so but it looks like it's a sealed system, please confirm thanks!

the mg guns don't need to be greased like say a IR 231, but, they still need to be oiled...few squirts through the air hole every few days is what i do