Air Compressor Knocking - how to fix?

[wes_k]

All - I recently bought a Snap-on AC580V air compressor off CraigsList. Snap-on still lists an AC580V in their current catalog, but pictures are very different, so they appear to have updated the model, and I don't know if parts for my older unit are available anymore. Seems to be a fairly nice compressor, but once I hooked it up at home, I found that there's a fairly aggressive knock above 40psi. The 5hp Dayton motor turns at 1740rpm, so I anticipated this to be a fairly quiet compressor, but once it reaches around 40psi, it starts knocking fairly aggressively. The pump is running at 760rpm (I checked with laser tach.), and I confirmed that the sharp knocking noise occurs at pump speed (12.7Hz.)

My untrained ear attributed it to something in the cranktrain (piston, rod, etc.), but reading online, some people seem to indicate that the reed valves might be a problem. Or possibly a restrictive intake (that's an easy one that I'll test later today).

1) I'm not sure who actually makes/made this compressor; does anybody know? Are parts available, and if so, where?

2) Any good way to identify the source of the noise?

3) If I need to rebuild it (and I can find the parts), where can I find the specs to check (bearing clearances, etc.)?

4) Any other help?


Thanks,
Wes

 

[BillK]

Reed valves shouldnt make a knocking noise. I would suspect the connecting rod bearing and crankshaft are torn up. You could get it warmed up and drain the oil out and see if it has a lot of metalflake in it. Either way I would bet you will be taking it apart.

 

[bullnerd]

I inherited a large, two stage craftsman that had a knock.

Ran for a long time with the knock. Company had it in a closet with zero venting!

I forget what happened when it finally quit, but when I took it apart, the large end of the rod was egged out and had about an 1/8" of clearance! lol!

 

[Kevin54]

Make sure your oil is changed and up to level. As far as a knocking noise, maybe look at the cooling fan. My IR has a plastic fan that came loose and made it sound like it was going to throw a rod.

 

[sberry]

Quit running it. Its likely broke. I had a Chanp spit a rod, gad an insert andcaught it in time, thats been 25 years ago, ran every day since.

 

[The Cobbler]

I would tear into it & see what is causing it, otherwise you'll very likely end up with a scrap (if not already) pump

 

[kazlx]

There's not much to them. It's pretty easy to take apart and just take a look before it destroys itself.

 

[nadogail]

I would tear into it & see what is causing it, otherwise you'll very likely end up with a scrap (if not already) pump

What he said.

 

[The Cobbler]

actually you can probably learn ( see) a lot by taking off the end plate on the crank housing

 

[csaws]

I have a horizontal Craftsman air compressor that I bought at a garage sale like 5 years ago, it is used on occasion and it knocks like mad. I can’t wait for the day it detonates so I can buy a new one [emoji51]


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