Hey! This site is reader-supported and we earn commissions if you purchase products from retailers after clicking on a link from our site.

by Bob Hall
(Browns Mills, NJ)

i have read your posts and and tore down my compressor. both reed valves are fine, gaskets look new, piston rings look fine to me, checked the little white valve that is in the copper tube that goes to the switch ….what else should i check?

The compressor runs but holds at 25 psi…note that due to not draining the air after use, i found a lot of dirty water in the tank when i removed the drain valve…could this have caused any damage to the unit? what else should i check and how would i check it?

Bob, good effort in trying to figure out what’s going on with your Craftsman compressor, and for the complete post. It helps me try to help you.

You say the air compressor holds at 25 PSI. I take that to mean that the compressor keeps running, and the pressure never goes past the 25 PSI, or does the compressor stop at 25PSI?

If the compressor shuts off at 25 PSI it’s the pressure switch that is causing the problem, I think.

However, if the pressure builds to 25 PSI and stays there with the compressor still running, and the motor doesn’t seem to overheat (indicating overload) then you have a pressure related leak I suspect, and even though the valves and the gaskets look good on visual inspection, I think that under pressure one or both of these items are leaking.

Use a lighted match at the intake port to see if any air is huffing out while the compressor is running. If so, it’s a valve issue.

If not, then I’m going with a pressure related gasket failure.


More details
by Bob

You are correct in that it keeps running…not sure if it would overheat as i never left it running more then10 seconds after pressure stopped building.

Will try the match trick and get back to you…where exactly do i hold the match near the intake…I don’t actually see any holes where it can be getting air into it? Will this test be affected by the air being blown by the big fan blade in the front..when i looked for leaks there was a lot of air moving around which seems to be from that fan


The issue is to determine whether the intake is pulling in air or huffing it out while the compressor is running.

Big fan?

What size of compressor and model is yours, Bob? You have posted on the page about 3 gallon Craftsman air compressors.


Still confused
by: Anonymous

Got it all back together (correctly i hope) and still no good….there is air coming out the fuel filter inlet…now that would mean bad valves right? but my valves look fine….is there something that could be wrong with them that i cant see?

i cant seem to definitively say i see any leakage from the gaskets also…kinda hard to tell with that big fan even though i tried to block it off…

Question of the thin metal gasket between the two valve plates…one corner of the two openings has a slight rise in the shape of a triangle…ho do i know where that should face? do i need to oil and of these valve parts or do anything special..used a little to hold the reeds in place



Not as much as I am now about what air compressor you are talking about.

Please add a few photos showing the overall compressor and one or two where you feel the problem is. Then we’ll proceed.