Air in Compressor Oil?

[mdbrandy]

I just fired up my new Porter-cable, 2 stage 80 gallon compressor. Breakin procedure is to run for 20 minutes without pressurizing tank. Compressor came with oil already in it up to the middle of the site glass. I added a little bit, but didn't want to overfill.

So, after 15 minutes of the 20 minute runtime, I noticed that the oil that I could see through the site glass was getting "frothy", and I could see some bubbles from the left side into the oil. I've never had a oil-lubed compressor before. Is this normal? There was no change in the sound of the machine, and it was still pumping air out of the outlet value normally.

Thanks.

Mark

[Phil V]

Your compressor is fine. There are "dippers" as an extension of the connecting rod lower part of the bearing cap. That dipper utilizes the oil splash system of lubricating the rod and main bearings as well as lubricating the cylinder wall/piston area. As the dipper splashes into the oil at the bottom of the compressor pump it forces a little air to be mixed into the oil. That I believe is where your air is coming from that you see in the oil in the sight glass. All is well in compressor land.

[mdbrandy]

Cool. Thanks for that bit of insight. I'd hate to see the oil in the crackcase of my car looking like that!