Just picked up a new Air Venturi HP compressor to replace my Carette ...........

Jason, You all are right. Years ago I worked as a production / equipment mechanic for 6 years and use to work on my own cars before they stated putting electronics and computers in them. That AV compressor ran for 10 minutes under no load what so ever with about 11 ounces of new synthetic compressor oil in it. I purged the O/W separator 2 minutes after I started it up and every two minutes for next 8 minutes. I can't believe this new compressor could bleed internal oil that black and dirty in that time frame. I am very troubled as to how this could of happened. New ISO 100 oil should not turn that black and dirty in a new compressor that quickly. The serial NO. is 2011280080 and it went thru a QC Test on 2020-11-18 It arrived at my home by Fedex on Thursday Feb 25, 2021. 


 
JKing correctly identified your problem. A friend of mine owned an AV that made that identical knocking sound once in awhile. The knock would start as the pressure reached 3000psi or more. It was spitting black goo out of the air bleed. The problem was caused by a failed high pressure piston ring. There was lots of burnt oil residue on the check valves and the lowest of the 3 piston rings was shredded. Over filling with oil and using motor oil both can accelerate this process. Never fill a Chinese compressor with too much oil. A little to low is better than a little to high. The occasional knock you here is oil dieseling in the high pressure piston chamber.

I'd send it back for a refund or replacement. Knowing what I know I'd either get a Yong Heng and stock up on replacement parts or buy a quality brand to begin with. By quality brand I mean Coltri, Alkin, or Bauer.


 
Humdinger, Thanks for the info. I think I might try one more time to get a good one. I reallly like to AV setup until the clunk started. I think it is worth another try. If the dealer will cover shipping this one back and send me a new one at no charge I will likely try it again. How long did your friend own his AV before the HP 1st stage seal blew?