Compressor Leaking from Check (?) Valve?

[Bolster]

Today, when I turned off my compressor, I got a leak from a schraeder-looking valve on the side of the switch box. As far as I can tell, the leak does not occur while the compressor is running, only when the compressor is switched off. For sure, air is hissing out of the "schraeder valve" (not really a schraeder valve but I don't know what to call it) when I place my hand near it.

In the manual's trouble shooting section there is a note:

"A defective check valve results in a constant air leak at the pressure release valve when there is pressure in the tank and the compressor is shut off."

If I move the little gold lever forward with my thumbnail in the direction of the green arrow, the leaking stops. When I let it go, it flops back onto the position seen in the photo, pressing the center of a gold colored schraeder valve, and will leak all the air out of the tank.

If I unplug the compressor, and switch to "on," then the leak stops immediately. But switching back to off (still unplugged) starts the leak again.

Recommendations? Thanks.

 

[Bolster]

Some more research on this lead to

According to this, the leaking air from the valve shown is merely a symptom; they say the cause is likely the check valve, where the "after cooler tube" (which sends the compressed air from pump to the tank) connects to the tank.

Recommended procedure is to disassemble and clean the check valve. Is this an operation a compressor novice can perform, or is it time to find a repair shop?

 

[zkling]

There should be nothing too complicated about taking apart and cleaning the check valve. Could be dirty, or could be worn out. I think that tube is actually an unloader for the check valve. I think that pressure switch operates off of a check valve / unloader combo.

Make sure you bleed down the system so there is no pressure in the tank or lines before you start working on it. Likewise I'd recommend that you unplug the unit before taking it apart.

 

[Bolster]

Will do! And thanks for the advice. See you on the other side (of the repair).

 

[G_P]

That needle valve on the side of the pressure switch is the unloader valve. When the switch shuts off it pushes the pin down releasing the pressure in the head of the compressor pump.

 

[The Cobbler]

That needle valve on the side of the pressure switch is the unloader valve. When the switch shuts off it pushes the pin down releasing the pressure in the head of the compressor pump.

and if it continues to leak air the check valve is culprit

 

[Bolster]

Ya, as I understand it now, the needle valve needs to purge the lines of compressed air, so the pump can start up easily when it needs to cycle again. Usually, that normal purging process takes a couple of seconds. But when it keeps purging your whole tank, then most folks suspect a defective or dirty check valve at the entrance point to the tank.

I am suspecting a dirty valve, as I had no problem until I loosened the air line from the pump to remove the piston head for a different issue. On reassembly, the check valve issue occurred.

When I pull that check valve out, I assume I can put it back using pipe dope on the threads?

And, just an idle question (no pun intended) -- do folks generally dump in some evap-o-rust at let it sit in the bottom of the tank for awhile, when they have to open the tank anyway? I'm expecting little or no rust (as I am a habitual tank drainer), but I was wondering if it would be worthwhile since I'll have access to the tank.

 

[Bolster]

Would you believe the check valve must have "self cleaned" because it's working again, and I didn't do a thing other than let the tank fill to capacity.

Ain't it great when tools fix themselves.