Dewalt Compressor Knock

[ishiboo]

I have a Dewalt DXCMV7518075 7.5HP I bought a few years ago for a great price, brand new from the store. I finally got around to wiring it up as I need the air, and it makes a pretty loud knocking sound that doesn’t seem normal. It has sat with a cover over it in my barn for a few years, it still looks good but has had a bit of dampness.

It had been factory filled with oil to the correct level, but I drained it and after a minute or two of runtime I don’t see any metal or anything in the oil. Pulled the cover that holds the bearing on the crankshaft, and I don't see anything hitting on the crank side, and it also doesn't turn hard with the flywheel. Nor do I really here much when I turn it over by hand.

Any thoughts? Video here: https://spacehog.s3.us-east-2.amazonaws.com/compressor-issue.html

Found another thread here but no answers at the time: https://www.garagejournal.com/forum/threads/new-dewalt-air-compressor-knock.458656/

 

[seber]

All piston compressors knock to some degree. Some are much louder than others. You might try putting a stethoscope on it and see where the knock is coming from.

 

[OccupantRJ]

I had two 25 hp Saylor Beale V4 compressors for 25 years at work that sounding like the rods were going to come out the sides in the morning until the pistons started getting loaded at startup. Nothing was found wrong with them, and they trucked on hard daily. How long have you run the unit at a time?

 

[ishiboo]

I had two 25 hp Saylor Beale V4 compressors for 25 years at work that sounding like the rods were going to come out the sides in the morning until the pistons started getting loaded at startup. Nothing was found wrong with them, and they trucked on hard daily. How long have you run the unit at a time?

Only has a minute or two of runtime, as I was afraid of doing permanent damage. There is a 30-minute break-in period where you run it with the air output fully open, so it's just dumping the air right now.

 

[Rinspeed]

I'm pretty sure those units are made by Sanborn. I would reach out to them and send them the link so they can hear it. Certainly sounds like some interference to me and they might be able to point you in the right direction to start, I wouldn't run it any more myself.

 

[whateg01]

I have a Dewalt DXCMV7518075 7.5HP I bought a few years ago for a great price, brand new from the store. I finally got around to wiring it up as I need the air, and it makes a pretty loud knocking sound that doesn’t seem normal. It has sat with a cover over it in my barn for a few years, it still looks good but has had a bit of dampness.

It had been factory filled with oil to the correct level, but I drained it and after a minute or two of runtime I don’t see any metal or anything in the oil. Pulled the cover that holds the bearing on the crankshaft, and I don't see anything hitting on the crank side, and it also doesn't turn hard with the flywheel. Nor do I really here much when I turn it over by hand.

Any thoughts? Video here: https://spacehog.s3.us-east-2.amazonaws.com/compressor-issue.html

Found another thread here but no answers at the time: https://www.garagejournal.com/forum/threads/new-dewalt-air-compressor-knock.458656/

I don't hear audio

 

[ishiboo]

I'm pretty sure those units are made by Sanborn. I would reach out to them and send them the link so they can hear it. Certainly sounds like some interference to me and they might be able to point you in the right direction to start, I wouldn't run it any more myself.

I believe this compressor, the Sanborn, Industrial Air, Masterforce, etc. are all made by MAT Industries, and I did reach out to them... but it's hard to find proper contact info.

 

[mreisner]

Only has a minute or two of runtime, as I was afraid of doing permanent damage. There is a 30-minute break-in period where you run it with the air output fully open, so it's just dumping the air right now.

If you briefly close the air outlet does it sound different?

 

[OccupantRJ]

I don't hear audio

I did not see the audio speaker icon at first either On my ipad. It was rather small.

 

[ishiboo]

Same noise under load, ran it up to 50psi.

 

[The Cobbler]

check to see that the flywheel is on securely. it does sort of sound loud, but it might just be the nature of the beast .

 

[Beerhippie]

On our old DVB, a loud knocking noise means it's running. Been doing it for a few decades now.

 

[MacMcMacmac]

Pull the filter. Block the intake and see if it changes. Some compressors just make an annoying pop when the valves operate.. This will completely unload the compressor and reveal if it is a mechanical knock.

This is a Cinese pump that lots of companies package and sell, including Sanborn and FS Curtis. I think LaPlante makes them.