Air Compressor Question

[William Batdorf]

Hello Creekers,
I have a 5 h.p. /60 gal. Craftsman air compressor in my shop. Recently it seems to run and run and run to build up air pressure in the receiver tank. To quantify that, I timed it...it took 17 minutes to climb from 60 psi tank pressure to 90 psi, then another 22 minutes from 90 psi to almost 120 psi, at which time I manually shut it off. That was with the tank valve closed (no parasitic losses in my piping layout). My initial thought was the pressure switch, but noodling it a bit more, I'm wondering if there are piston rings that are the problem in the compressor? Never had one of these apart. Any thoughts or ideas? Thanks in advance.

[Rod Sheridan]

If you had that much blow by in the rings I would expect it to have blown the oil out of the crankcase.

I would start with unloader valve, check valve and reed valves in that order……Regards, Rod.

[Ronald Blue]

While it could be rings it would be odd that they fail catastrophically. This is a piston type compressor? It would have a reed valve which could fail or there could be something stuck under one as well. Not knowing anything about this specific compressor I don't know if it might have an unloader valve or not. This is to aid in starting and if so equipped could be not seating fully. Just spit balling here and more info could be helpful. I'm sure other knowledgeable people will chime in soon.

[Greg Quenneville]

How is the air filter? I wonder how mine is for that matter since it’s been a long time since I looked at it.

[Richard Coers]

Here's a trouble shooting guide. https://www.ccinetwork.com/images/media/Air%20Compressor%20Troubleshooting%20Guide.pdf
Interesting one is water in the tank. Do you drain it?

[Robert Hayward]

I had a head gasket leaking on a small one of mine a while back. Similar symptoms. I was gong to toss it then a buddy asked if he could look at it. He made a gasket out of a paper of some kind and the compressor is still working.

[Michael Schuch]

Is it a direct drive oil-less compressor or a separate pump and motor?

If it is an oil-less compressor I guess it is time for a new one. If it is a belt drive compressor I would get a spray bottle of soapy water and start spraying, especially around the head gasket before starting to disassemble the pump.

Is the pump low on oil?

[John K Jordan]

Is it a direct drive oil-less compressor or a separate pump and motor?
If it is an oil-less compressor I guess it is time for a new one. If it is a belt drive compressor I would get a spray bottle of soapy water and start spraying, especially around the head gasket before starting to disassemble the pump.
Is the pump low on oil?

Oil should be changed as per the schedule.

I'd check for external leaks around the compressor - I use kid's soap bubble solution to find air leaks, it's incredible. I don't know how to check for internal leaks.

I have an IR 5hp 60gal 2-stage piston compressor. I just checked and it went from 100psi to 160psi in less than three minutes. If mine took as long to pump up as described and I could hear no hissing with the motor off (and the motor and belt drive appeared good) I might tear down the compressor and look for clues.

JKJ

[Bill Dufour]

Single or two stage? Turn it on and go outside so your ears are working good. As soon as it shuts off at max pressure listen for any air leaks including tank drain.
Bill D

[Carl Beckett]

Although if it is a diaphragm type compressor the diaphragm may have failed. Some of the consumer models are diaphragm, even at '6hp'. A pic would tell.

[Charles Lent]

Many compressors have reed valves, and the flexing of these makes them break. If you don't find any leaks, you quite possibly have broken reed valves in your compressor. In the ones that I've worked on these valves are all in a plate that is fitted between the cylinder and head. Replacing it is easy, if you can find the replacement, but there may be other damage from the broken pieces of the reeds bouncing around in the cylinders after they broke off, scoring the walls of the cylinders, etc.. I ended up buying a replacement compressor, of a no-name brand, but keeping the tank, motor, and controls. It was cheaper than what they wanted for a new reed valve plate, and this was for a Sears/Craftsman Air Compressor before Sears closed. You may be able to get parts you need through Lowes now, because they bought Craftsman Tools from Sears, but I doubt you will find the experience financially to your benefit.

Charley

[Dave Cav]

I bought a 5 hp red Craftsman air compressor, probably 70s vintage, for cheap because it wouldn't pump up. I pulled the head and the reed valves were bad. I cut some new ones out of a pop can and it was still going strong 15 or so years later when I sold it.

[Bill Dufour]

The reeds can get so rusted that the no longer seal well. They can be wire brushed/sanded and reinstalled. That is one reason I installed an old oil bath air cleaner on my compressor.
Bill D

[Curt Harms]

I cut some new ones out of a pop can and it was still going strong 15 or so years later when I sold it.

I guess that's one way to get around the "this part is obsolete or no longer available":). Good job.