Old air compressor

[acosta3492]

Can anyone tell me the manufacturer of this air compressor pump, and any other information?

 

[MacMcMacmac]

This is a United States Air Compressor model MK pump.

 

[acosta3492]

This is a United States Air Compressor model MK pump.

Thanks Mac....that helps. Trying to find out as much as I can. I did see MK marking on the top of one of the cylinders.

 

[acosta3492]

Got another question. Got a small air leak. In 10 minutes losses 5 psi. I sprayed soapy water on ALL thread fittings and no bubbles anywhere. See attached pictures. I circled the 3/4 check valve in the one picture...could that check valve be leaking air back up into the cylinder head. How can I check to see if it's faulty? Also the small tube that runs from the head down to bottom of the pump, is that the pressure bleed off for the cylinder heads? Is that for allowing the motor to start easier, the pressure escapes from the heads by way of the tube? I don't really hear anything from the end of the tube when the pump stops on set on pressure. Would like to be able to keep the tank pressurized without the motor kicking on for days if possible.

 

[The Cobbler]

small tube that runs from the head down to bottom of the pump, is that the pressure bleed off for the cylinder heads? Is that for allowing the motor to start easier, the pressure escapes from the heads by way of the tube?

yes

could that check valve be leaking air back up into the cylinder head. How can I check to see if it's faulty?

yes, it can be leaky . since your discharge line is soldered it would have to be cut apart ...but basically just take the line off the check valve spray soapy water in there & look for bubbles... or not.
to me it looks like a water check valve, not a pneumatic check valve , I'd be suspect
but, did it lose pressure right away ? heated air cools & becomes smaller so it will lose pressure at first . if it continues to lose you have a problem

 

[acosta3492]

Thanks for your comment....it loses complete pressure in about 2 hours. I did check the water drain valve at the bottom of the tank with soapy water...no bubbles. Yes ,would have to cut the main copper air supply line because it's soldered. There looks like there's a screw in cap on the main air check valve, wondering if there are parts inside that could be replaced. Going to take it apart. Don't know if I could even find internal replacement parts for it.

 

[RTM]

Going to take it apart. Don't know if I could even find internal replacement parts for it

But a good cleaning might be all it needs.

 

[acosta3492]

Lol....not with my luck!!!
But will give it the old college try...lol.

 

[micromind]

If you remove the cap on the check valve, there'll be a spring and some sort of a disc that seals against the body of the valve. There's a good chance the disc has some guck on it, cleaning it will help.

 

[acosta3492]

Yes....I will try cleaning the disk up....thanks for the help.

 

[acosta3492]

Ok....bubbles out the unload tube....see bubbles..?lol. I opened the main inlet check valve. Clean it up to no avail...still leaking. I ordered a new check valve. I'll let you guys know how it goes...thank again for everyone's help....talk to you Gents later.

 

[acosta3492]

Thanks ...tried to clean it ,didn't work. I replaced with new check valve. New valve did the trick. I other question, thinking about changing the oil..what type do I use?

 

[The Cobbler]

good on the repair job!
as far as oil, Mineral based compressor oil , either 20 weight or 30 weight . I would go with the 30 if it's in a heated place in winter.
or you cab use synthetic compressor oil,
Just don't use detergent oil .