Rings for an old air compressor

[Iron Beaver]

Hey everyone, first post here.

I have a Craigslist special Curtis ML-5 compressor that I just set up a few months ago. The other day I noticed it builds pressure much slower from 160-170 PSI than from 50-60. also that there is a detectable stream of air coming out of the crankcase breather. Does anyone know of a source for rings for this pump? It looks like the design has changed since Curtis became FS-Curtis so I'm not hopeful that I could get new ones. I would much rather not have to buy a whole new pump.

 

[marinusdees]

Last time I checked, Curtis is still in business. I bought parts from them about 5 years ago. Google them. If you want a source for rings many small engine rings fit air compressors.Get on your computer.

 

[MacMcMacmac]

ML = Masterline which is their heavy-duty industrial pump. There should still be parts available for it.

 

[nadogail]

If you can't get the rings from Curtis, try an an automotive machine shop and parts supplier near you.

Back in my high school days I worked in one and we were able to come up with rings for orphan engines based on the numerical section of our piston ring catalog.

Because I graduated from high school in 1958, you might have to ask to speak with the oldest employee at the company.

 

[sberry]

Not many of them have worn out rings that lose comp. Main reason for replacement is oil going by.. of course it builds that 10# slower,, it's pump g against 160 vs 50. Lots more stored energy.

 

[Iron Beaver]

I'm not worried that it's slower per se, but that it's slower plus if put my hand in front of the crankcase breather I can feel a detectcable stream of air. Not big, just detectable. Plus because I have a dirt floored shop that constantly has gritty dust in the air, I assume a lot of that could have got past the filter.

 

[Citation]

It's possible there is nothing wrong with the rings. I'm just going to offer an anecdotal story. Last year I saw a Craiglist ad for a $10 Campbell Hausfeld oil lubed, direct drive roofing compressor. The seller said it worked but the dipstick kept blowing out of the crank. When I got it home I pulled the head to check the bore. The bore was nearly new looking. That got me thinking, you aren't going to have bad rings but a clean bore. So then I compared it to my older Emglo roofing compressor. Hey, if I pull it's dipstick I feel the same amount of air blowing past. I assumed this was normal and then tried to figure out why the CH dipstick was blowing out. Then I realized it didn't screw in like the Emglo and the o-ring had taken a set and wasn't holding the thing in via friction. So really, the only problem with the whole thing was an old O-ring that had taken a set.

In the OP's case I wouldn't outright assume this is a problem. If you have spare head gaskets then pulling the head to look would be a good idea.

 

[sberry]

If you pull the head run it with the head off for a bit, if it pools oil on the pistons the rings are bad. If it's got a crank breather maybe it's sposed to be breathing there?

 

[RADcustom]

...or back the pressure down to 150 and let you kids deal with it.

 

[Iron Beaver]

It seems like the consensus is that the pump may not be bad. That was one of my questions, so thanks everyone for all the answers!

This is the first "real" air compressor I have ever used (plenty of flimsy jobsite units before this) so I am kind of shooting in the dark about how much blow-by is normal.

That leaves me with dust. Is it likely an issue? The dirt floor of my shop raises large quantities of really fine grit when anyone is in there. Enough that I have to wipe down all the ways on any machine tool before I use it. I have been obsessively checking the air compressor filter and it remains clean. Then again, I don't know how good those little paper filters are.

 

[Iron Beaver]

I should add. There is no oil in the air that I have been able to detect. I assume my plasma cutter would be telling me about that in a hurry if there were.