Knocking noise from Compressor

[Mmfh]

Hey there,

My small daily runner compressor has been making a lite knocking noise for awhile now, the last few days its been getting a lot louder and at the rate its going sounded like it was going to blow if I didn't tear it down and fix it.

Sounded like a rod knock. I would have bet the bank that one of the rods were going to be hammered and done.

I took it all apart and found nothing, rods, pistons, cylinders, crank, bearings, everything looks good. I'm actually surprised because I've used the hell out of this thing and in 10 years I might have changed the oil once.

Only thing I can figure is the reed valve assembly must be making noise. You can't take it apart as its riveted together and you can't even see the surface that seals. I honestly don't see how this assembly could make a loud knocking noise but I don't see anything else.

One thing I noticed before tearing it down, when you fired it up with an empty tank is was very noisy, as the pressure got up to about 100 it would quiet down a lot. Almost no noise at all.

Here lately and why I took it apart is the noise that would normally go away just kept getting louder. I really didn't like running it because it sounded like it was self destructing.

This is a Coleman Powermate, 60 gal, 6.5 hp. Aluminum pump with iron cylinders. 220 volt , single phase. Pump number 165

Have you run into a pump that knocked like crazy and it turned out to be the valve assembly that was doing it?????

I really hope so as I'm not seeing a knock anywhere else.

Thanks very much!

Mm

 

[gregthor]

I had a knock in my speedaire that turned out to be a loose pulley/flywheel. Sounded just like a rod knock. Was the pulley/flywheel tight when you took it apart?

 

[PowerDubs]

I bought 2 matching compressors from Lowes last summer. One makes some knocking when it starts up, the other is quiet and makes no noise. I was wondering myself if it was a rod knock.

It hasn't got any worse yet, but I've only used it maybe 10 hours total run time so far.

 

[G_P]

Check the belt? I have seen belts with a chunk missing make some racket especially if it is shaking the whole machine enough.

 

[Mmfh]

The flywheel was very tight, I had to get after it with a puller and it didn't want to let go. Belt seems fine, no cracks and no chunks missing anywhere.

When I say this thing was noisy, I mean I listened to the knocking noise for a long time and it wasn't really getting any worse. Last few days it progressed to the point that I was sure rod and crank were getting torn up by the minute.

Inside looks good and no metal in the oil. Oh and the unit ran smooth, with the exception of the knocking noise it ran fairly quiet too.

 

[pipsters]

Did you check the belt tension?

 

[Mmfh]

Did you check the belt tension?

Belt tension was good.

 

[Mmfh]

Anybody else have any knocking compressor stories?

 

[RangerDaleXp]

I had a knock in my speedaire that turned out to be a loose pulley/flywheel. Sounded just like a rod knock. Was the pulley/flywheel tight when you took it apart?

interesting point, I have a speedair doing the same time and I will look into that.

 

[b-body-bob]

I've got an old DeVilbiss that sounded like it's going to fly apart > 100 psi. Below that it's quiet. Got to looking around and found one leg floating over the bricks I've got stuck under them, and the flywheel was loose. Corrected all that and all is well or at least better.

I guess since the OP has torn his pump down and put it back together it wouldn't be his flywheel, but posting that here just in case someone in the future runs into a problem.

 

[j.c.whitney]

My Champion Porta-Champ (small 1-cylinder compressor) makes a knocking noise like a rod is going out, the oil is full, the unit functions normally but that knock is bothersome. When it beaks, I'll either fix it or buy another compressor. Been going on several years like that.

 

[Altec]

If it is knocking, you really should answer the door.

 

[Chris.Santamarina]

Hey there,

My small daily runner compressor has been making a lite knocking noise for awhile now, the last few days its been getting a lot louder and at the rate its going sounded like it was going to blow if I didn't tear it down and fix it.

Sounded like a rod knock. I would have bet the bank that one of the rods were going to be hammered and done.

I took it all apart and found nothing, rods, pistons, cylinders, crank, bearings, everything looks good. I'm actually surprised because I've used the hell out of this thing and in 10 years I might have changed the oil once.

Only thing I can figure is the reed valve assembly must be making noise. You can't take it apart as its riveted together and you can't even see the surface that seals. I honestly don't see how this assembly could make a loud knocking noise but I don't see anything else.

One thing I noticed before tearing it down, when you fired it up with an empty tank is was very noisy, as the pressure got up to about 100 it would quiet down a lot. Almost no noise at all.

Here lately and why I took it apart is the noise that would normally go away just kept getting louder. I really didn't like running it because it sounded like it was self destructing.

This is a Coleman Powermate, 60 gal, 6.5 hp. Aluminum pump with iron cylinders. 220 volt , single phase. Pump number 165

Have you run into a pump that knocked like crazy and it turned out to be the valve assembly that was doing it?????

I really hope so as I'm not seeing a knock anywhere else.

Thanks very much!

Mm

If the knock is really that bad it usually turns out to be the wrist pin bushings on the piston or the insert bearings that connect the connecting rod to the crank. This model may have the pressed in insert bearing and not the split type that are found on some larger pumps like the Quincy. Ingersoll Rand uses the one piece style connecting rod. The reed vales usually don't knock that loud as supposed to drop-in style valves when not seated.

Chris

 

[Mmfh]

I bought a gasket kit and also a valve assembly, reed valves, and put it all back together. Same knocking noise, spent $50 and still the same thing. Started doing a little more checking and pulled out the one way valve that is in the top of the tank, comes right off the pump and into the tank.

If you blow into it you can feel the valve open, it required me to blow fairly good before it would open but it did open, blowing the other way it would not let the flow go through.

That all seemed good, I took the valve anyway and soaked it in WD-40 over night. Played with it the next day and really loosened it up so blowing on it was much easier than it was before to open up the one way valve.

Installed and found it to have made a big difference! Not completely quiet but much better, I feel if I bought a new valve it will be totally quiet again. They are about $22 for this compressor.

So, if you have a knocking noise like maybe a rod knock, check the one way valve going into the tank from the pump. Seems like it should open fairly easily, that made a big difference on mine.

Mm

 

[osborn.ozzy]

My grandpa had one that made a hell of a noise, They key on the shaft was almost sheared off.

 

[Justin1776]

I second the wrist pin. There is a large by huge duplex compressor at the school that I am remodeling. It supplies air for the HVAC controls throughout the entire school. One of the compressors lost a wrist pin bushing a few months ago. When it ran, you could barely stand next to it, it was audible from several hundred feet outside the building.

 

[Chris.Santamarina]

I bought a gasket kit and also a valve assembly, reed valves, and put it all back together. Same knocking noise, spent $50 and still the same thing. Started doing a little more checking and pulled out the one way valve that is in the top of the tank, comes right off the pump and into the tank.

If you blow into it you can feel the valve open, it required me to blow fairly good before it would open but it did open, blowing the other way it would not let the flow go through.

That all seemed good, I took the valve anyway and soaked it in WD-40 over night. Played with it the next day and really loosened it up so blowing on it was much easier than it was before to open up the one way valve.

Installed and found it to have made a big difference! Not completely quiet but much better, I feel if I bought a new valve it will be totally quiet again. They are about $22 for this compressor.

So, if you have a knocking noise like maybe a rod knock, check the one way valve going into the tank from the pump. Seems like it should open fairly easily, that made a big difference on mine.

Mm

The valve you bought is a tank check valve. Its so the unit can shut down and unload the air in the discharge tube from the pump to the tank. This stops the pump from starting up under a load by keeping the air in the tank and the discharge tube and head empty of air. I do not think even if you replace the valve completely you will see a huge difference. As the pump makes air and more pressure the high pressure piston is put under more of a load you will still hear the knock. If you can take the pump apart check the wrist pin bushing. If you snap the rod due to too much play in the bushings it could put the rod through the crank case. I have seen this hundreds of times in the field.

Chris

 

[Chris.Santamarina]

I second the wrist pin. There is a large by huge duplex compressor at the school that I am remodeling. It supplies air for the HVAC controls throughout the entire school. One of the compressors lost a wrist pin bushing a few months ago. When it ran, you could barely stand next to it, it was audible from several hundred feet outside the building.

What model is the duplex? I usually see some style Quincy pump for those applications. If it is a Quincy check the oil pump pressure. Be sure that it is between 18-22psi on the oil pump gauge. If its not it will knock like a mother. It also helps seal the unloader and allow the pump to make air. Just a thought. It could just be a bad knock as well, but worth looking into.

Chris

 

[Mmfh]

The valve you bought is a tank check valve. Its so the unit can shut down and unload the air in the discharge tube from the pump to the tank. This stops the pump from starting up under a load by keeping the air in the tank and the discharge tube and head empty of air. I do not think even if you replace the valve completely you will see a huge difference. As the pump makes air and more pressure the high pressure piston is put under more of a load you will still hear the knock. If you can take the pump apart check the wrist pin bushing. If you snap the rod due to too much play in the bushings it could put the rod through the crank case. I have seen this hundreds of times in the field.

Chris

I took the pump apart and measured everything, all the clearances are good. Including the .0005 on the wrist pin bushings, .003 rod to crank, .003 piston to cylinder. Rod side play is about .010, crank end play is next to nothing. Everything inside the pump looks as if its only run for a short time.

A little reminder, this knocks between about 50 psi and up to 100 psi, after that its quiet, before that its quiet. But did knock hard between those pressure points.

Mm

 

[Chris.Santamarina]

I took the pump apart and measured everything, all the clearances are good. Including the .0005 on the wrist pin bushings, .003 rod to crank, .003 piston to cylinder. Rod side play is about .010, crank end play is next to nothing. Everything inside the pump looks as if its only run for a short time.

A little reminder, this knocks between about 50 psi and up to 100 psi, after that its quiet, before that its quiet. But did knock hard between those pressure points.

Mm

That's strange. The reed valves wont knock, and the tank check doesn't either. It will chatter as the pulse of air passes through it, but not knock. Knocking at higher pressure is almost always a pin bushing knock or insert bushing issue. Those little pumps don't have too many moving parts that would cause a knock.

Chris

 

[Justin1776]

What model is the duplex? I usually see some style Quincy pump for those applications. If it is a Quincy check the oil pump pressure. Be sure that it is between 18-22psi on the oil pump gauge. If its not it will knock like a mother. It also helps seal the unloader and allow the pump to make air. Just a thought. It could just be a bad knock as well, but worth looking into.

Chris

Its a Quincy. The school board sent out one of their HVAC guys and he rebuilt the one compressor. We turned off the bad one and ran the school on the single pump until he showed up (a few weeks later....) The compressor is slated to be "removed" once we have fully converted to low voltage controls
Thanks for the heads up about the correct oil pressure, for future use.