I may have posted up something about this a while back, but I finally got a semi-decent video to show what I’m talking about. Basically, it’s a 60 gal compressor I bought from Northern Tool about 2 years ago. Here’s a link to some specs, the compressor has now been discontinued: Amazon.com: – Industrial Air Cast Iron Pump Compressor – 3.6 HP, 60 Gallon, Model# ILA7006056: Home Improvement

When the compressor kicks on, it starts pumping, then slows down pretty drastically. Over the course of 3-5 minutes, it will slowly build up speed. I thought maybe the pump was starting to seize, so I tore it down and couldn’t find anything wrong (cylinder bores still had crosshatches). I thought it was the pressure switch, so I replaced it with a new unloader valve, still the same thing. I checked the check valve on the top of the tank, seems to move freely.I cannot figure out what the problem is! Tank is only at about 55psi when I flip the switch on

BTW: Someone had mentioned to me that it could be the motor, but when this first started, I heard the belt slipping on the pulley. IT doesn’t do this in the video, but if that’s the case I don’t see how it could be the motor.

Here’s the link to the video. it’s in .3g2 format, I’m working on finding a converter if others cannot view this file type.

EDIT: Found a cheap converter, got it in AVI format as well

3G2 File (2.5 MB)

AVI File (15.3 MB)