Where is thew check value on my old Kellogg compressor!?

[nicke]

Where is the check value on my old Kellogg compressor!?

I noticed the other day that my compressor sounded like it was leaking through the pressure switch, but only when the motor wasn't running. I thought it was my pressure switch finally going bad, so I bought a new one, and threw it on there.
Same issue! Everything seems perfect as the tank is getting up to pressure with the motor running, but sure enough, as it reaches pressure and the motor cuts off, air starts rushing out through the unloader valve on the new (and Old) pressure switch.
So, after a bit of research, I sounds like I might have a faulty check value
For the life of me, I can't figure out where that is. Please help!
Pics of my setup are below:

Thanks
Nick

 

[The Cobbler]

at the tank where the line from the compressor head enters

 

[nicke]

The last two pics show opposite sides of the compressor, both with lines from the head entering the tank. Which of those might it be, and particularly, which part is the check valve? It isn't that big rectangle shaped component in the second to last pic is it?

-Nick

 

[nicke]

Guessing this must be it, no?

 

[OccupantRJ]

That should be it.

 

[sberry]

You can clean them on occasion.

 

[nicke]

Thanks guys! I'll get it out of there and see about cleaning/replacing.
Thank you!

-Nick