Anyone here ever rebuild a 2-stage air compressor pump?

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Old 05-04-10, 11:28 PM
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Anyone here ever rebuild a 2-stage air compressor pump?

I never have, but apparently I'll be doing it in a couple of days. Any advice on accomplishing this in a day? I have a ton of tools, but no ring sleeve(s).

My plan is to remove the pump from the compressor first. Remove the head next and then seperate the case. (Reversing the process to reassemble.)
 
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Old 05-05-10, 12:26 PM
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What exactly do you mean by rebuild? Most problems with piston compressors are valve related.

If you need new rings you will also need to hone the cylinder walls. Connecting rod bearings on the crank end are usually Babbitt and the piston end are pressed-in sleeves. The main crank bearings are usually balls but you need a press to remove them. If the crank throws are worn or damaged you will need the crank turned/ground and the connecting rods crank ends re-Babbitted. Depending on the compressor the valves may be reeds on non-replaceable seats or they could be cartridge style.

If you plan on getting everything done in a single day you would have to have a mighty complete machine shop with the facilities to turn/grind crankshafts and do bearing pours and finishing. Quite honestly, unless this is a larger machine (over 15-20 cfm) or all it needs is a valve job, you are probably better off buying a new pump.
 
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Old 05-05-10, 10:06 PM
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The valve plate is shot. It's leaking alot around the high compression cylinder.

Rebuild kit includes piston rings as well as all the necessary gaskets to replace all the old ones. It also has the most important valve plate that I really need.
 
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Old 05-05-10, 11:01 PM
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I've used a worm gear hose clamp as a ring compressor. You might try an automotive parts store to see if they rent engine tools but the compressor piston, especially the high pressure piston, may be too small for a regular ring compressor.

Be sure to completely clean the ring grooves (use a piece of broken ring) before installing the new rings. The slightest bit of carbon can cause you to break the ring when re-installing in the cylinder. As I wrote before you really should hone the cylinder, at least enough to "break the glaze" or the new rings will never "seat" and the compressor will likely pump oil.
 
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Old 05-05-10, 11:42 PM
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Originally Posted by furd View Post
Quite honestly, unless this is a larger machine (over 15-20 cfm) or all it needs is a valve job, you are probably better off buying a new pump.
It's a 25 cfm pump. The rebuild kit costs $360, which I can barely afford. The pump cost about $1,200, which I don't currently have.
 
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Old 05-06-10, 10:15 PM
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Funny...

Originally Posted by furd View Post
I've used a worm gear hose clamp as a ring compressor.
I just bought 2 hose clamps. I think I might be able to pull this off. (or not)
 
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Old 05-08-10, 05:14 AM
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curious..

Why are you changing the rings if the problem is in the head?

Have you determined that the old rings are bad?
 
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Old 05-08-10, 11:41 AM
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I agree with Markiz, unless the machine has broken rings don't change them. New rings will require cylinder honing.
 
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Old 05-08-10, 01:57 PM
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Okay.

Originally Posted by furd View Post
I agree with Markiz, unless the machine has broken rings don't change them. New rings will require cylinder honing.
The rebuild kit I purchased included a new cylinder/crankcase o-ring and piston rings. Let's say I only replace the cylinder head assembly and seals (assuming the cylinder walls and piston rings look in reasonable good condition. If I don't get good pressure and determine after re-assembling that the piston rings really should be replaced as well, should I be able to reuse all the o-rings if I run the compressor for a week and am not pleased by its performance still? My parts distributor really would like me to do a full rebuild (including piston rings) to bring the compressor back to virtually new condition.
 
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Old 05-08-10, 03:09 PM
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Just a general observation----


DIYers often do a minimal quality repair job because they do only the minimum they think will be necessary to get something to work. They often lack the skills and tools to do a more thorough job.

I do this myself when I'm working outside of areas where I'm a properly equipped Xpert.
 
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Old 05-08-10, 05:03 PM
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Originally Posted by SeattlePioneer View Post
DIYers often do a minimal quality repair job
I actually intend to perform a high-quality repair job, so I'm trying to postpone the ring job until it can be done properly. I need to find a reliable shop that has the equipment to hone the cylinders (and possibly re-install the pistons with the new rings, which I'm still considering doing myself).

I've clearly determined there is a leak in the valve plate assembly. I can replace that part easily with less than 3-4 hours of downtime.

Oh... I also have a spare intercooler assembly and discharge assembly. Those occassionally fail too.
 
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Old 05-09-10, 05:02 AM
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nice kit!

If it came with new honed cylinders, by all means go ahead and replace the whole works. I just never heard of a rebuild kit that included a cylinder block
 
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Old 05-14-10, 03:48 PM
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Finally got to it...

Originally Posted by markiz37 View Post
If it came with new honed cylinders, by all means go ahead and replace the whole works. I just never heard of a rebuild kit that included a cylinder block
Cylinder walls look really good. Valve plate had a crack in the high-compression cylinder. Intercooler tube has a few leaks in it. Discharge tube fitting was also cracked. I'm losing pressure everywhere!

Thanks for the help from you and furd. Had trouble diagnosing the problem (since I actually had 3 problems!).
 
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Old 05-19-10, 09:39 PM
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Final followup...

maybe?

The manufacturer fused the cylinder head to the valve plates for the replacement parts. Unfortunately that throws the length of the discharge tube off by about 1/8th inch. I stressed the fittings alot to just get good seals, but I'm thinking something will stress. The distributor is trying to determine if the manufacturer modified the specs. I'm using a laser to determine distance, so I doubt it's off by 3/32s (at least).

The pump sounded weird on startup. It sounded way more base-y. More of a thump that a whistle sound.

I ran it for 30 seconds with the drain-**** open. I repeated this 6 times in minute intervals, building up to about 65 psi. Found a couple of minor leaks that I was able to eliminate. I then closed the drain-****. Took 3 more 1 minute intervals to bring it up to 160 psi. Looks like my pressure switch is corroded. It should hit about 175 psi.

I'll wait to hear back from my distributor, but I can't see how I won't end up replacing the discharge tube in the near future.
 
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Old 05-20-10, 07:34 AM
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Originally Posted by ImCurious View Post
I can't see how I won't end up replacing the discharge tube in the near future.

Do it, man. You don't want too much stress in there or the vibrations of the pump will destroy it. In fact, get a piece of braided ss hydraulic flexible hose, it'll do nicely. Otherwise, congrats on the rebuild and a job well done.
 
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Old 05-20-10, 07:02 PM
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Originally Posted by markiz37 View Post
Do it, man. You don't want too much stress in there or the vibrations of the pump will destroy it. In fact, get a piece of braided ss hydraulic flexible hose, it'll do nicely. Otherwise, congrats on the rebuild and a job well done.
Thanks... and again thanks (to you both) for the suggestions/feedback. I used it for real today.

From this experience all I can say is "if you think your compressor might need some service, remove the word 'might' from your statement." The longer cycling times and higher noise levels kind of sneak up on you (or at least me). You just don't notice the subtle changes over time.

I still need to replace the pressure switch, but:
Compressor noise level is a fraction of what it was. (can actually talk without screaming while it's running)
It cycles from 0psi to 160psi in about 3-4 minutes (used to be about 8-10 minutes).
It now only runs for about 90 seconds per cycle with a full load. (used to be 3.5-4.5 minutes with a very light load)
It stays off for 3-4 minutes before restarting with a heavy load(used to be 4-5 minutes with a very light load).

And, sadly, after reading this site, doing a few searches and spending some time at the supplier's web site... I know much more about air compressors than I would ever like to know. But I really do enjoy the education I receive here. It's always stimulating and thought provoking.

Thanks,
Jeff
 
 

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