Air Compressor Pump ?

[LFD2037]

I have a Speedaire air compressor. It's a horizontal unit w/a ~30gal. tank. The pump makes some odd noise that sounds like a rod knock. I know nothing about air compressor pumps. Is this fixable/rebuildable? I looked for a replacement pump but they're pretty pricey.

[CabezaBlanca]

Tear it apart and look inside. You’ll find out quick if it’s a rod bearing. I’m sure it’s rebuildable.

[LFD2037]

Tear it apart and look inside. You’ll find out quick if it’s a rod bearing. I’m sure it’s rebuildable.

I can do that. What's inside it? I'm assuming it's an average crank/bearing/rod/piston pin/piston set-up like an internal combustion engine?

[double bogey]

Yep, and reeds for valves. Speedaire parts should be available. Grainger sells them i believe. What hp are you talking about?

Check out these guys

https://www.aircompressorsdirect.com/tools/air-compressor-pumps.html?msclkid=a29d0731bd3d1f2a34d259b37640460a&utm_source=bing&utm_medium=cpc&utm_campaign=Accessories&utm_term=air%20compressor%20pumps&utm_content=Pumps

[RifleBowPistol]

I had one of those style compressors many years ago. It got what sounded like a rod knock, I took it apart and found the cylinder wall was wiped out, had a lot of wear. I think the cylinder wall was aluminum, not sure on that. I know I was not happy with the way it was made, don't remember the brand, that was probably 28 years ago. I have found things like that are usually all made pretty similarly.

Won't know till you get it torn apart, but probably time for a new one.

[Done'it]

It could be a blocked screen in the line that goes from the pump to the tank. Mine was at the tank fitting

[LFD2037]

Yep, and reeds for valves. Speedaire parts should be available. Grainger sells them i believe. What hp are you talking about?

Check out these guys
https://www.aircompressorsdirect.com..._content=Pumps

I looked for that info. but didn't find anything on the pump. It has a Dayton electric motor. Would the HP be on that or the pump?

I had one of those style compressors many years ago. It got what sounded like a rod knock, I took it apart and found the cylinder wall was wiped out, had a lot of wear. I think the cylinder wall was aluminum, not sure on that. I know I was not happy with the way it was made, don't remember the brand, that was probably 28 years ago. I have found things like that are usually all made pretty similarly.

Won't know till you get it torn apart, but probably time for a new one.

This is a quality unit, made in USA with a cast iron pump. I don't know if it has an aluminum sleeve in the cylinder jug, though.

It could be a blocked screen in the line that goes from the pump to the tank. Mine was at the tank fitting

It fills fine w/air, no problem. It just sunds awfully loud w/that knock. Did yours fill up w/air okay?

[double bogey]

Hp should be on the motor. It may only have fla, or rla. Typically a 30 gal portable will have a 2 to 5 hp motor.

115V, usually around 7 amps per hp. 230V, half that.

Look up your compressor model on grainger and see what the specs are.
cfm@psi. hp advertised. Use that data to search for a replacement pump.


A knock with anything reciprocating is usually a rod bearing, or a wrist pin bad.
Some larger compressors are worth rebuilding, smaller ones not worth the labor, at least paying a pro's labor. for myself, my labor is pretty cheap.

The speedaire/grainger model number should be on the tank somewhere, the compressor should have a tag also.

[Bubbabowhunter]

Check the big pulley on the compressor to see if the set screws came loose.

[LFD2037]

Hp should be on the motor. It may only have fla, or rla. Typically a 30 gal portable will have a 2 to 5 hp motor.

115V, usually around 7 amps per hp. 230V, half that.

Look up your compressor model on grainger and see what the specs are.
cfm@psi. hp advertised. Use that data to search for a replacement pump.


A knock with anything reciprocating is usually a rod bearing, or a wrist pin bad.
Some larger compressors are worth rebuilding, smaller ones not worth the labor, at least paying a pro's labor. for myself, my labor is pretty cheap.

The speedaire/grainger model number should be on the tank somewhere, the compressor should have a tag also.

I found the tag. Speedaire model 4B227D. 20gal., 2HP, Pump #4B246A.
I'll see what I can figure out now that I found this info.

Check the big pulley on the compressor to see if the set screws came loose.

I'll check that.

[LFD2037]

Rings: $75
Piston: $22
Rod: $44
Crankshaft: $64
Entirely new pump: $253
Maybe I can find a knock-off pump for cheaper. Looks like I'll have to tear into it before I know which direction to go. Thanks.
Do all compressors of this size have the same footprint for the pump (ie. other brands are interchangeable)?

**ETA**
Just went out & started messing with it. It ran for about 10 seconds, quit & won't do anything now. To the trash it goes!
Thanks to everyone who tried to help. Have a great day & stay safe!

[double bogey]

Did the motor quit? If the pump was seizing the motor would cut out on an internal overload. Cools off it will run.

[LFD2037]

I said forget this one and got on Craigslist. Found a new one an air compressor company was selling. Got it for $200!

[double bogey]

Where do you live? Did you throw away your old one?

[LFD2037]

Where do you live? Did you throw away your old one?

I’m in northern Ellis county. I haven’t trashed it yet and you’re more than welcome to come get it tomorrow. It’ll be trashed after that.