by Larry
(Illinois)

I have a Craftsman 12 gallon 125 PSI 1 HP portable air compressor.

Last fall I changed the oil in it. Like an idiot i didn’t read the manual first and overfilled it. After sitting all winter I fired it up to do some work around the house. After using it a few times I started noticing the odor of oil burning coming from the compressor.

Now it will only build to 40 lbs. of pressure but keeps running with no increase in pressure. When I drained the tank I notice the water was mixed with oil.

When I turned the compressor off it did not bleed down so no leaks. Did I break it for good? What do I do? Thanks.

Craftsman 1 HP air compressor

Craftsman 1 HP air compressor

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Larry, offhand, I would guess that you have damaged the piston seals at least, since you have lube oil mixed with water in the tank.

All oil lubed compressors wick oil into the tank with the compressed air. However, it shouldn’t be too much, and if you are seeing it, then I suspect that the sump oil has forced its way past the piston seals, then down the line into the tank.

See the troubleshooting page about compressors that run and don’t build pressure for more info.


And another issue… Oil coming out pump oil fill vent – too much oil?

My compressor 60 gallon upright is only 2 years old don’t use it very much.

I was using it the other day blowing out a hay baler and when I got done there was oil blowing out the oil filler vent.

I have not change the oil yet and the oil level is fine.

I have never had any trouble before also the pump and motor was pretty warm but never shutoff due to overheating.
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Typically this scenario can be caused by overfill of the oil sump and vibration is splashing oil up and out the fill vent.

Since you haven’t filled the oil recently, another reason this will occur is that your piston seals are leaking air, it gets past them down into the sump, the sump is vented to allow air to escape, and the escaping air is taking oil with it.

You mention that you were using the compressor to blow out a hay bailer. Did you move the compressor to get it to where you used it?

If the oil sump is full, moving the compressor could have allowed excess oil to migrate into the fill tube, and then, vibration could be splashing oil out.

It depends on how much oil.