Can anyone help me with an air compressor issue?

[Robert Engel]

Hey guys its an Ingersoll Rand 5HP with dual piston SS5 compressor. About 10 years old, light to moderate use.

A couple weeks ago it suddenly started making a very loud noise (I mean VERY loud), honestly I thought it was going to blow. The shop was filled with oil smelling mist.

I don't know how long it was running like that, I immediately shut it down. I checked the oil it was slightly low, but in the eyeglass.

A couple days later I turned it on just for jollies and it ran up to pressure and shut down. I used it for a few days, then noticed it was short cycling - running for 5-10 seconds and shutting off. Then the other day it started making the loud noise and just shut off.

I've been trying to find a compressor service that can look at it, without much luck.

I decided to take the head off and have a look. When I turned the flywheel, I did hear a scraping sound but the cylinders look good to me - no signs of scoring. I don't know if the deposits on the valve plate are normal.

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Trying to decide to buy a new compressor pump, or can it be fixed. Thanks.

[Thomas C Barron]

Obviously, it’s either the motor or the pump.


Normally, if the motor goes bad it gives off a burning smell. If a winding wire breaks it can give off a clacking sound like a fan or cards in your bike spokes. You didn’t describe any of these observations.


I would guess the noise is a rod knocking. The clue to me is your note saying it started making a loud noise and then shut down by itself before reaching shut-off pressure.


The motor will only shut off under the following:


It reached max psi and shut off normally


The motor got hot and thermal shut it down


Low oil pressure sensor


The clue to me is the oil mist and smell. It sounds like bearings and rod

[Scott T Smith]

I had something similar happen with my 7.5hp Campbell Hausfeld compressor. Turns out that the big end of the connecting rod had worn quite a bit and was allowing the piston to hit the head.

[Edward Dyas]

It would probably help if you would describe what the loud noise sounded like. Your description suggests something has gone awry with one of the pistons since you can smell oil. If the pump is blowing air into the reservoir that would cause it to smell like oil. The tank also has a one way valve so the pipe going from the pump to the tank can be emptied when it's done running. That way the motor doesn't start under a load. If it has failed the motor has a hard time starting and belts can screech and the motor can get hot quick. The pump has valves in the head that open and close so the pistons can work independently from each other. They are usually just flat pieces of sheet metal. If one has failed it can blow air into the other cylinder on the down stroke.

[Bruce Wrenn]

A broken ring would be my guess, especially the oil ring. This would explain the oil mist