Compressor startup rattling noise explained

[Humdinger]

It can be scary when a new owner starts up an Alkin or Bauer compressor and hears that paint can rattling noise. It stops as soon as a drain valve is closed. The sound is actually the free floating third stage piston which stabilizes under pressure. The rattling piston causes no damage but it is disconcerting. It sounds like something has broken loose inside the compressor. There is a recent Youtube video by a new Alkin owner showing an initial 10 minute break in run. He left drains open the entire run and the rattling continues non stop. He could have closed the drain valve and left the fill hose open to release pressure. Ayden at Alkin headquarters told me that all Alkins are broken in and tested before shipment so no break in run is required. It comes fully tested, contains oil, and is ready to run. The purchaser only needs to attach an outlet plug to match their receptacle type.

 

[grackleblast]

Exactly correct. My Airetex 45 sounds like a washing machine full of roofing nails when I first fire it up! I try to run it for about 5 minutes every couple of weeks, and will never get used to that "broken" mechanical sound. I find that closing one or two bleed valves (my compressor has 3) that the offending rattle is quickly gone rather quickly. In over 5 years of ownership, it still bugs me.

 

[Centercut]

Yup, my AireTex Mini Magnum (Bauer Junior 2 clone) does the same thing... As soon as I close the 2nd stage cyclone separator vent it stops...

 

[bubblerboy64]

Yep. It’s an impressive sound. Tell the wife what ya paid for that compressor then start it up. Look up at her and smile. She already knows you’re “ not quite right” just further proof. Don’t bother explaining that there is actually nothing wrong because she knows that it’s the same sound her car made right before parts flew off the engine after that time you changed her oil ( the cars oil) and forgot to put the new oil in.