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  1. #1
    Member
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    Mar 2005
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    Tucson, AZ.
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    Rebuilding an air compressor pump

    Hey everyone:

    I gambled and bought a used Speedaire (Dayton - Grainger) air compressor from a guy on Craigslist for $50. Its from the early 80's, all cast iron, oil lubricated pump, nothing metric, made in USA...

    I think I may need to rebuild the compressor pump because when I drain the tank, after the air and moisture is gone, oil drips out of the drain and makes a pool about 6" dia. I've never owned an oil lubricated compressor, so I am guessing this is not normal. Also, I unscrewed the top of the regulator and there was oil in it as well. I'm looking at all of this and thinking that oil is getting past the compressor pistons where it shouldn't.

    It looks easy to remove everything. Should I dive in and figure it out myself - or is this something that I should have fixed by a professional?

    Anyone have experience with doing this?

    Thanks,
    Bryan

  2. #2
    Sonny Edmonds
    Guest

    RE: Rebuilding an air compressor pump

    "Should you dive in and fix it yourself" ???
    Chit! Is that ever a loaded question! How the heck should we know?
    Are you proficient in mechanical stuff?

    Chances are you bought a fairly well used and probably well worn compressor.
    I would try and clean out the tank and piping first to establish how much oil it uses (sucks by the rings).
    While it is pumping up after that, go online and see about parts for it. That would determine if it is worth the work, or if a new pump would be a better route.
    For $50, I wouldn't put a lot of change into it myself.
    You could tear it down for the experiance, then replace it.

    :D

    [link:home.earthlink.net/~pie/data/index.html|Sonny Edmonds ]
    Saugus, CA
    "Precision Firewood Specialist"

    "Lurkimus turdius orifus" (Limey-speak latin for a lurking A$$hole)
    A handle bestowed on me by my Dear Friend, Robert "Limey" Bolton. 1947-2007

    "A candle loses nothing lighting another."


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  3. #3
    Member
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    Mar 2005
    Location
    Tucson, AZ.
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    RE: Rebuilding an air compressor pump

    I'm not bad at fixing mechanical things. I have more success stories than failures, so far. I've never messed with compressors though. I was just wondering if rebuilding a compressor was tricky or not.

  4. #4
    Member
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    Dec 1969
    Location
    Buchanan Dam, TX, USA.
    Posts
    301

    RE: Rebuilding an air compressor pump

    Another dimension of "is it worth the trouble" is this: How much would a compressor with comparable capabilities (assuming you fix the compressor) cost? If you can get a compressor with higher flow and/or higher pressure and/or larger storage capacity (granted, oil-less, I'm sure, but mine has run for several years without any problems) at the BORG for a couple hundred bucks...is it worth your time and trouble to fix it, considering the cost of the overhaul kit if one is available?

    Most of the commonly available compressors today will supply plenty of ***pressure***; it's the ***volume*** that gets us in trouble. If you look at the specs of your air tools, you'll see that they are rated to perform at a certain pressure and a certain volume. For example, 4 cfm @ 90 psi. Then you have to look at what the compressor will supply - will it supply 4 cfm @ 90 psi? If it doesn't supply what your air tool requires, you'll run out of air to run your tools and you'll have to stop long enough to let the compressor refill the tank.

    I have a P-C compressor with a 30-gallon tank (IIRC), but the compressor shuts off at 175 psi, making the tank ACT like a substantially larger tank when using tools that require only 90-100 psi. I bought it several years ago at Sutherland's on a day when they were having a pretty good sale, and it only cost me something like $225, which was a STEAL at the time. For my purposes, it runs everything I need to run just fine, including an occasional air ratchet.

    I have a buddy who faced a similar problem - the compressor head was worn out. However, the storage tank was just fine. It dawned on him that his compressor never moves, so portability isn't an issue. he bought a brand new compressor, trashed the old compressor head, and plumbed the old storage tank into his air system WITH the new compressor, giving him a new compressor with effectively twice the storage capacity. He runs air ratchets and impact wrenches (both known air hogs) without any problems now.

    I've never tried to run a sand blaster or paint gun with my compressor, so I don't know how it would work. I think those are both even bigger air hogs than ratchets/wrenches, so I tend to doubt that it would do the job. Your mileage may vary, with approved credit, etc.

    Let us know what you figured out.

    phil

  5. #5
    Member
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    Dec 1969
    Location
    Bradford, Vermont, MerryCanna.
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    18,751

    RE: Rebuilding an air compressor pump

    Shouldn't be very tricky at all - certainly less so than rebuilding a small engine (example: lawn mower engine). The results... well, that compressor has probably been in operation essentially since Day One... which makes it a veteran of about 20 to 30 years. I'd guess it's got steel sleeves in it, which to my mind ranks high in importance for a long-lived compressor. Remember when the Chevy Vega was introduced, and it had all-alumin(i)um cylinders, and it was good for exactly 75,000 miles before it burned a gallon of oil getting to the gas station? Once sleeved, it became a good little motor.

    Yeah - at this point ya oughtta' see just how fast it's suckin' oil. If it's not too bad, you can put an oil separator on the air line & recycle the compressor oil back to the compressor. If it's really bad, more than you're willing to deal with, then what do you lose by yanking that compressor apart? Nada. Get it apart & see whatcha' got, then make the final decision from there. Could be you've got a broken ring - that's an EASY fix. Could be, though, that you've got badly scored cylinder walls... that's a little harder to deal with unless you can sleeve it.

    You don't have an oil injector right in the air line, right? As to lube an air tool? That could even explain the extra oil, maybe.

    -- Tim --

    Member of the
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  6. #6
    Sonny Edmonds
    Guest

    RE: Rebuilding an air compressor pump

    When you begin to dismantle it, you will need gaskets or the ability to make them.
    You might be able to anneal the head gasket if it is copper and reuse it.
    Then you will need to see what the cylinder(s) look like. If scored, it gets iffy.
    And if you decide to continue the disassymbly, plan on rings and being able to disassymble and reassymble the crankshaft and rod. And being able to hone the cylinder.
    Maybe a piston and bearings.
    It can become not cost effective to rebuild it.

    [link:http://www.grainger.com/Grainger/cat...nt-parts/parts | Here we go, grab your butt with both hands and smile.] }>


    :D

    [link:home.earthlink.net/~pie/data/index.html|Sonny Edmonds ]
    Saugus, CA
    "Precision Firewood Specialist"

    "Lurkimus turdius orifus" (Limey-speak latin for a lurking A$$hole)
    A handle bestowed on me by my Dear Friend, Robert "Limey" Bolton. 1947-2007

    "A candle loses nothing lighting another."


    [h1]Welcome to the Forum![/h1]
    http://smileys.smileycentral.com/cat/15/15_4_132.gif
    God Bless America !
    In God We Trust !



  7. #7
    Member
    Join Date
    Mar 2005
    Location
    Tucson, AZ.
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    30

    RE: Rebuilding an air compressor pump

    I'm gonna dig in and take the head off. Mostly for the challenge, but also I don't want to spend a bunch of $$ having someone else tell me I need a new compressor.

    I like Phil's (preyn2) idea of using the tank as an external storage tank. It's in good shape and holds air. I may plumb to it if the compressor looks grim!

    Thanks for the suggestions. I'll let you know what happens - and maybe send a picture.

    Bryan

  8. #8
    Member
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    Bradford, Vermont, MerryCanna.
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    RE: Rebuilding an air compressor pump

    MAYBE??? I'm not THINKIN' any dang ol' MAYBE... post 'em for show & tell!

    -- Tim --

    Member of the
    Robert "Limey" Bolton Memorial
    International
    Volunteer Mentorship and Assistance
    Programme

  9. #9
    Member
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    Dec 1969
    Location
    Port Coquitlam, British Columbia, Canada.
    Posts
    1,798

    RE: Rebuilding an air compressor pump

    Pull the head off and take a look at the cylinder walls, some Speed Air pumps have a plastic button that holds the wrist pin in place, if this wears out the wrist pin will move sideways and score the wall.

    If the rest of the compressor is in decent shape you can always put a new pump on it for a couple hundred dollars, sometimes less.

    Sawdust Making 101
    http://sawdustmaking.com
    Frank C

    Sawdust Making 101
    http://sawdustmaking.com

  10. #10
    Member
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    Sep 2004
    Location
    Huntington Beach, California, USA.
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    RE: Rebuilding an air compressor pump

    Bryan,
    After reading the comments of others, I can offer some advice on things not mentioned.

    With the head off, there is probably a ridge in the cylinders that can be felt. Just put your finger on the cylinder wall and slide it to the top of the cylinder. If there is a ridge there you'll be able to feel it. There is a cheap tool, $20-$30 that is designed to remove the ridge. You will have to remove the ridge if you install new rings. If you don't, the new rings will hit the ridge and either the piston or the new ring will break.

    Typically, all piston rings are similar. The rings are classified by function and size. The rings are designed for a certain size hole, the width of the groove in the piston and the depth of the groove in the piston. If the rings from a '39 Buick match the function and size, you can subsitute the ring in your compressor.

    If you still have one of those engine rebuild shops in your area you should be able to have the cylinders rebored. Then just use new rings that match the size of the over bore. If you're really lucky, the engine rebuilder may be able to install the new rings for you at a small charge.

    To install the new rings, you'll need another tool, a piston ring compressor. If you can't find one localy, one can be made by using a radiator SS Band clamp and a piece of metal cut from a coffee can. (DAMHIKT)

    Finally, there is something called taper. This is expressed as a difference between the cylinder diameter measurements at the top and the bottom of the cylinder. As an engine wears a taper is created by the wear. In a gasoline engine, 0.030" taper almost mandates that the cylinder be rebored. This is also an "Out Of Round" condition in the cylinder. In the old days we could rebore the engine block three times with the results being 0.030", 0.060" and 0.090" over bore. Usually going beyond 0.090" over resulted in block failure and water in the crankcase.


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