Air compressor acting funny, what gives?!

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Andre68

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Okay so I bought a 60 gal. 3.7hp 155psi kobalt air compressor from lowes about 3 or so years ago. It's worked great up until recently...

The issues.
About 6 months ago it began to bog down (sound weaker) at around 90psi, for about 30 sec. And then it would return to normal. I thought nothing of it as I don't know much about air compressors and it still would work fine.

Then the issue began where it would start to screech, and crank about 1/4 to 1/8 at a time. Then spin a couple times and then some times completely just come to a hault. So I run over there and shut it off, kick it on a few times until it starts running normal again.

Now it's at a point where it's just running weak. It will start normal, then begin to bog down when it starts getting hot, then do the screeching and 1/4 turn stuff, then it will start to come in and out strength wise. Normal then bog, normal then bog, etc.... I noticed it seems to do better when cold.

I now the belt is original and I can smell that belt burning when it's doing that odd cranking thing. Belt looks pretty saggy. So I take it, I need a new belt... That may fix the weird cranking, because the belt won't be slipping and it would be gripping good. Not sure if it would fix the bogging down though...

Does anyone know what's going on with the compressor? And how is it fixed?

Thanks!
 
This oiless or not? Sounds like an oil / lube problem. "It may be too late" at this stage.

Could be motor problems. Take the belt off immediately after it's gone into one of these screeching / stalling modes and see if the motor and compressor spins as it should
 
It is oil type.

Okay will do, I will take the belt off and run it and see how it goes. See if it makes the screeching noise still.

How long should I let it run for? A few minutes?
 
If so, try a new belt, when it is bogging down, I'll bet you a dog turd to a doughnut the electric motor is still spinning normal.
 
Belt sagging at all, tighten or replace it whichever it takes. "Belt looks pretty saggy"
Compressors are hard to turn when the pressure gets up and if the belt isn't tight it'll do exactly what you describe.
Take Roy's advice and I'll bet he's right.
 
Yea I always made sure to keep it oiled, and would change it out every couple months. I would use the recommended kobalt brand as well.

Yea I would drain it out after use. Not gonna lie... There been a few times I have forgotten until the next day. Just a few times though....

What would cause the lack of lube? Always made sure it was at level.

So it's the pump that could possibly be bad? Vs the motor?

I could have recalled hearing some sort of knocking coming from the pump as well. The last 30min before I shut it down completely.
 
Sounds like the compressor is on the way out.
 
Adjust/replace belts, clean air filters, replace 1/4 of oil with "duralube" .

If it's in a confined area, perhaps supply an auxillary cooling fan.

jmo..
 
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famous bob said:
sounds Chinese to me. bought mine at lowes, wish I hadn`t !
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I got mine at Lowes too. It's a little Cobalt. But it has a cast iron twin cylinder pump. So far so good. American made things are so far out of reach now for a lot of people.
 
RustyRatRod said:
I got mine at Lowes too. It's a little Cobalt. But it has a cast iron twin cylinder pump. So far so good. American made things are so far out of reach now for a lot of people.
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I have the same (or very similar) one. I've lightly abused it and it's still up and kicking. Wouldn't try to run a commercial shop with it, but seems fine for 'hobbyist' use...
 
Compressor will have a lot less condensation if you run a garden hose for inlet air to somewhere inside the house, rather than suck outdoor air.
If you live in a region with low humidity anyway, that shouldn't be an issue.
 
Ben Drinkin said:
I have the same (or very similar) one. I've lightly abused it and it's still up and kicking. Wouldn't try to run a commercial shop with it, but seems fine for 'hobbyist' use...
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Lemmie tell yall a couple of little secrets with these newer compressors they are makin nowadays. First, the tanks are thin. Not dangerous, but thinner than they used to be. So they don't last as long.

Secret number one. Shop ONLY for a compressor that has a TOTALLY cast iron compressor. Not an aluminum pump with cast iron sleeves, but a COMPLETELY cast iron compressor. Even the Chinese find it hard to screw up cast iron.

Secret number two. Take your NEW compressor home, un-box it and strip the tank bare. I know. It's a little bit of a PITA. Take the tank to your local radiator shop and have it coated, just like you would a gas tank. BAM. Instant compressor tank that will never rust.

Secret number three. Almost 100% of these import compressors run the pump WAY too fast. Generally, you want your pump speed to be around 750 RPM. You can figure all that out with this new stuff called math. Get you a smaller pulley for the motor and slow that pump down. It will run cooler and probably last forever.

Compressor manufacturers make the tanks thin and make them run fast so they will wear out and they can sell more compressors. If you do these few things, plus regular maintenance, they can last virtually forever. It only takes hand tools to disassemble a compressor. Nothin to it.
 
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Adding a check valve right at the outlet of the compressor will also take a big strain off the valves in the compressor, and may make it run much more quietly on the intake side.
 
Darthomas said:
Adding a check valve right at the outlet of the compressor will also take a big strain off the valves in the compressor, and may make it run much more quietly on the intake side.
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Compressors are supposed to already have this. There are several different methods, known generally as "unloader."
 
Darthomas said:
Adding a check valve right at the outlet of the compressor will also take a big strain off the valves in the compressor, and may make it run much more quietly on the intake side.
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I have never seen one without it.
 
I added check valves on two that friends had years ago, because they were hard to start until they had run down to about 50 psi, or they would smoke the belts.
 
Darthomas said:
I added check valves on two that friends had years ago, because they were hard to start until they had run down to about 50 psi, or they would smoke the belts.
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Then the unloader was not working to start with. A check valve, by itself will not unload the cylinder head. There are several methods

One is "automatic" This is a check valve that has a bleed hole. When the compressor stops, the check valve closes, and the movement of the piston in the valve uncovers a bleed hole

The most popular for 1/2--3hp class compressors used to be built into the pressure switch. You can always tell these unloaders, because there's a separate tube leading to the pressure switch

Others use a mechanical link on the compressor itself, I guess they are centrifugal. I have no idea how many kinds. If an unloader is properly working, you can usually hear the "hiss" of it unload when it shuts down. Another way is to crack the tube going to the head. Releasing pressure there shows it is not unloading, or the check valve is leaking back
 
As some have said. As the pressure builds up the difficulty of turning the pump increases. Add loose belts to the equation and you will get the screeching noise of the belt slipping and slower turning (bogging) of the pump. You can try and tighten the belt first but if it has been slipping for awhile it may continue to do so.
 
RustyRatRod said:
Secret number three. Almost 100% of these import compressors run the pump WAY too fast. Generally, you want your pump speed to be around 750 RPM. You can figure all that out with this new stuff called math. Get you a smaller pulley for the motor and slow that pump down. It will run cooler and probably last forever.
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Rusty, does doing this reduce the output of the compressor? IE. if you slow the pump speed in half, wouldn't it cut the cfm in half as well and take twice as long to fill up? Just curious, as this sounds like a really good idea.

To the OP- those Kobalt compressors (and husky's for that matter) are just re-badged campbell hausfeld units. I'd call them and see if there's anything they can do. Wouldn't hurt to ask at least. My Husky 60gallon compressor is no shop compressor, but it does everything I need it to and then some. Plus, I bought it new for under $400 at Home Depot. As Rusty said, not everyone needs or can afford a $1500-up industrial compressor.
 
mopowers said:
Rusty, does doing this reduce the output of the compressor? IE. if you slow the pump speed in half, wouldn't it cut the cfm in half as well and take twice as long to fill up? .
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It absolutely reduces CFM but it may not be a linear curve. If you look up some bare pumps, there is probably a chart. I've got one that has always been troublesome. It's a microV and has a tiny motor pulley with a 3450 motor. This means of course that the motor pulley must be much smaller than if it were a 1725 RPM.
 
Sure, it reduces the CFM somewhat, but at the cost of increased longevity. Unless I am sanding or paint a car.......which I probably never will again, I will have all the air that I need.
 
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