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Air Compressor Making Weird Noise – Loud, Rattling Air Compressor Noise

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Get help and support when your air compressor starts making a strange noise, with existing problems and solutions from the community for a broad range of air compressors brands and models.

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My 1988 Craftsman DeVilbiss Air Compressor Is Making strange clunking noise?

by Daniel Shortt

(Travis AFB, CA)

I recently bought a 1988 model Craftsman air compressor made by DeVilbiss. It has a 3 hp electric motor and a 20 gallon horizontal tank.

Overall the compressor looks to be in great shape for it’s age.

I have done small upgrades to the plumbing on it and just made it look more presentable.

The only concern I have is when it is building pressure at around 40 psi maybe and about 60 psi again it makes a loud clanking or rattling sound. I have tried feeling all over the compressor as it runs and can’t find where the problem could be coming from.

At all other PSI-s it runs quiet and smooth and it also builds pressure quickly and easily.

The noise is a pretty loud and distinguished sound. Am I OK to keep using it like this and what are my possible troubleshooting steps?

I have changed the oil since buying it also. Any ideas? Thanks.

Clunking Noise From Air Compressor Could Mean Loose Belt

Response by Bill

Typically, Daniel, clunking or clanking noises can be cause by a too loose belt, belt misalignment, mounting bolts loose, and then into the heavy stuff, perhaps a bearing issue inside the pump.

I cannot hear the noise, nor can I see the compressor as I can find no image of it. Perhaps you might upload a photo or two?

If all mounting bolts are tight, if the belt is correctly tensioned and aligned, and there is no impact of visible moving parts on stationary components, then, I’m going to have to go with a bearing issue.

That will mean a tear down of the pump, unfortunately.

Follow up

by: Daniel Shortt

I have checked everything that was mentioned.

I have taken apart and re-assembled the whole assembly other than the actual compressor itself. I will probably take it apart and have a look inside the compressor this weekend, what should I be looking for?

Would you say it is the bearings on the connecting rods? Also, I can provide pictures of the compressor if it helps.

Wear Marks Could Indicate Worn Bearings

Response by Bill

Difficult to be certain. Wear marks, sloppy bearings….

Yes, please upload photos.

Why is my air compressor all of a sudden making a loud knocking noise?

By peter

(greene, ny 13778)

Oil level is good, just recently changed, in a heated garage?

It could be a mechanical issue in your pump

Response by Bill

Hello Peter. I get asked this question periodically, and really, since I cannot see the air compressor running, or hear it while it is making this noise, you don’t identify the compressor or the model, so I really don’t know how to answer the questions.

If the motor is still mounted securely to the mounting plate, and the pump is too, then either it would be a mechanical issue in the pump, or the motor shaft rotating and hitting.

It might be a loose centrifugal switch inside the motor cap, for example.

Can you not isolate the knocking to a specific compressor part or area and add a comment with that information and the make and model?

Sanborn has knocking noise at 120 PSI

I just purchased a 60 gallon sanborn compressor, and when the pressure reaches about 120psi I hear a knocking noise. It doesn’t make any noises from 0-120psi.

Nov 11, 2014
knocking noise resolved
by: Anonymous

I took the guard apart and I noticed the belt was loose, causing the knocking noise. I adjusted the belt tension, turned on the compressor and the noise was gone.

I really appreciate your help and concern, thank you.

Nov 11, 2014
Knocking Sanborn
by: Bill

You want to get the cover and belt guard off and have a look at the various components while it’s running.

That it starts knocking at 120 PSI suggests to me that back pressure is increasing the load, that load is being transmitted back to the drive and the motor, and the knocking may be related if there is a loose mount or part.

It still would be good to get a model number so folks can go find an image on line to try and help you with your Sanborn compressor problem.


Nov 10, 2014
knocking noise
by: Anonymous

I bought it brand new from princess auto, it’s a 60 gallon sanborn compressor. The cut out pressure is 135psi. When it reaches around 120 psi I hear a knocking noise somewhere around the motor and the belt guard. When I touch the plastic cover I feel the knock.

Nov 10, 2014
by: Doug in s.d.ca

You bought this new? or used?

Can you describe the noise more fully? What is the model and cut-out pressure?

New comment? New question? Please add it here along with photos to help others help you with your compressor and equipment problem!

By Bill Wade

About Air Compressors has been helping folks with their Air Compressor Problems since 2002 online. We're a community of DIY and Compressed Air professionals who are keen to support everyone across the globe with their air compressor issues and troubleshooting. Whether you're trying to identify an old air compressor, or troubleshoot an error code on a sophisticated new industrial air compressor - the community at About-Air-Compressors.com is here to help you

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