# Bogged-down Craftsman compressor



## spavined (Feb 16, 2010)

All,

Finally fed up with the lack of capacity my 6-gallon (oil-less) compressor provided, I recently bought a used 5hp 33-gallon craftsman. I bought it off a chiropractor who said he didn’t use it very much and who knew less than I do about it—which is not saying much. He ran it for me for ~30 seconds when I bought it, and it ran well.

After the hour-drive home, I unloaded the unit and plugged it in. It ran well for about 5 minutes, but then something happened and it really started to run poorly; it sounds like it’s getting bogged down, like the motor is having a hard time driving the compressor. I loaded a short video on youtube here: http://www.youtube.com/watch?v=p-toEKTBkLE 

The only thing I can tell you that it seems to be losing a good amount of oil out of the bottom gasket, which appears to be shot. I noticed it was even spraying a little bit of oil as it ran while it was running well. This seemed bad, but I’m not sure whether it’s the cause, related to the cause, or unrelated to the cause of the problem.

I’m pretty comfortable with engines and taking things apart (I rebuild old motorcycles), but I don’t know anything about air compressors. If someone could please give me some idea as to what this problem may be and how I troubleshoot it, I would appreciate it.

Thanks in advance – I really appreciate any thoughts.

Thanks,
-s


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## jlhaslip (Dec 31, 2009)

drain the air tank before messing with anything.
pull the head off and look for cylinderf wall scoring and bad rings.
might be sleeved? might be a bad gasket. hard to determine. rip it apart to find out.
Craftman parts should be easy to get.


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## spavined (Feb 16, 2010)

Looks like that's the solution for troubleshooting. Thanks for the response - I'll let you know if I find anything interesting.


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## Thurman (Feb 9, 2009)

I watched the video--the motor is straining under an abnormal load. Note the motor moving radially within it's mounts. Something in that cylinder is binding. You're a bike mechanic, I'm a compressor mechanic. The jug needs to come apart--for sure. There should be no compression within the bottom of the cylinder, I'm suspecting a cracked/broken ring here which allowed some compression into the bottom which helped blow out an already loose bottom cylinder gasket. That's why it starts fine and then begins to strain--equal pressure(s) on both sides of the piston. Therefore: hard to run after a minute, and oil blowing out the bottom.
I'm thinking these newer (Red) units have the aluminum cylinders, whereas the older (Green) units had a C.I. sleeve within the aluminum cylinder. Hopefully the cylinder wall is not scored too bad and can be honed. There could be a cracked piston, odd in these smaller units but has happened. I would suggest searching Sears Parts.com for parts breakdown on this unit and availability of parts. Check the "Reed" (intake/exhaust) valves on this unit while the head is off. They often get a slight rust build-up on them and won;t seat well. They can be cleaned with oil and fine emery cloth. Check the check valve while it is down also. The tube (copper usually) from the head goes into the check valve, which is screwed into the tank. Wash it out with carb cleaner, blow through as if blowing into tank, should not be able to blow the other way. You can do this, and that's a decent unit when running properly. Keep us posted. Good Luck, David


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## spavined (Feb 16, 2010)

David, This is great, great information - thanks a bunch. Give me a few days - I'll keep you posted. -s


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## spavined (Feb 16, 2010)

I tore down the compressor, and I expected more parts. In any case, here is where I am:

Exhibit A
Exhibit B
Exhibit C

Several findings:

Of note: gaskets were blown. Wired for 110, but probably should be 220.

Good news: no broken rings or piston. Cylinder walls look good.

Bad news 
#1: I'm fairly positive this is not the original compressor. When I got to taking it off, I only then realized it didn't fit the original mounts. It has no features I can find to tell me its make or model.

#2: Due to the above, it looks like I'm going to have to make all my new gaskets, which is not my preference. They differ from those seen on the sears parts site.

#3: Am I correct in thinking this is a piston short?(!)

Assuming "yes" to #3, is this my issue? Why would it run fine for a while before, though? I can't make the logic work there. If not the issue, is it simply the loss of pressure from very bad gaskets? Can I safely run this on one cylinder? If I need two pistons, I have no clue where to get the right hardware for this replacement compressor.

The reason I'm not positive about the # of pistons is the sears diagram for the original compressor shows two cylinders but only one piston. This makes no sense to me, but I'm new to this technology...

I appreciate any further thoughts, thanks.


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## Maintenance 6 (Feb 26, 2008)

Yeah, it's short a piston. And that's where the problem starts. Existing cylinder is pressurizing the crankcase and blowing the gaskets and spraying oil. Also why the motor is bogging down. It might be just as cheap to buy a rebuilt pump and have a known product than try to find pieces. especially since you don't have any true info on this one.


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## spavined (Feb 16, 2010)

I figured as much. If there's an upside, expensive lessons are usually the ones I learn the most from...

Thanks, all.


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## Thurman (Feb 9, 2009)

Thanks for the pics. What you have is indeed an older twin-cylinder compressor unit, may/may not be Craftsman. They did sell these type units years ago, quick/large volume at moderate pressures. * Not* to be confused with a two-stage unit, more on that. You/ the compressor is one piston short, that's the problem. Now--consider what it would take to get _this_ unit up and running, assess what _you _need in an air compressor. Then compare parts cost, do figure in your free time, the fact that this is an older unit/hard to find parts, and add this all up. You're a bike mechanic, I'm betting you've done this with bikes. Is it worth it, as compared to what you _need _in a new unit? You're call. IF you decide to rebuild--I do wish you the best. IF you decide to replace, save that tank--it will make extra air storage or maybe a portable tank. Good Luck, David


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## spavined (Feb 16, 2010)

Update: Things are progressing. After a few conversations, the prior owner of the compressor and I have come to an understanding about a few things. The result is he's sending me back 75% of what I paid him and I'm keeping the unit. I've rewired it to 240V (13A), which is a return to its original set-up. Seeing as the cylinders are in fine shape, I'd planned rebuild the compressor; however, seeing as I have no sense as to the original manufacturer (there's no identifying marks or numbers), this has proven challenging. This morning I called a couple of commercial compressor shops to see if they had any ideas for aftermarket rods and pistons that could match what I've got, but both told me I was out of luck. This leaves me with a couple of questions for you all: 1. There are serials on the piston and rod I have (VS-1-A and VT-1-B, respectively). Does this mean anything to anyone? An internet search unsurprisingly didn't find anything. Any other ideas for finding aftermarket pistons? 2. Unless something turns up for (1), I'll probably just buy a new compressor unit with the money I'm getting back from the prior owner. To this end, I've been looking around and have found both 3hp and 5hp options--the latter generally being considerably more expensive. If the only difference between the two is air delivery levels (i.e. max PSI and max RPMs are otherwise the same), is there a reason the 3hp compressor couldn't/wouldn't/shouldn't be put to work connected to a 5hp motor? Thanks, -s


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## firehawkmph (Dec 12, 2009)

Spa,
Just curious once again, how much money will you have tied up in this unit if you buy another pump? I bought a 5hp single stage with a 60 gallon tank over 15 years ago for less than $400. It still works great, powers all my air tools and my large blasting cabinet from TP tools. I still see similar compressors for less than $500.00. Just wondering if you might be better off going the new route. 
Mike Hawkins


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## spavined (Feb 16, 2010)

But what fun is that? 

(With a new pump, and importantly with the money he's returning, I will still be in the $200s)
-s


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## Maintenance 6 (Feb 26, 2008)

spavined said:


> Update: Things are progressing. After a few conversations, the prior owner of the compressor and I have come to an understanding about a few things. The result is he's sending me back 75% of what I paid him and I'm keeping the unit. I've rewired it to 240V (13A), which is a return to its original set-up. Seeing as the cylinders are in fine shape, I'd planned rebuild the compressor; however, seeing as I have no sense as to the original manufacturer (there's no identifying marks or numbers), this has proven challenging. This morning I called a couple of commercial compressor shops to see if they had any ideas for aftermarket rods and pistons that could match what I've got, but both told me I was out of luck. This leaves me with a couple of questions for you all: 1. There are serials on the piston and rod I have (VS-1-A and VT-1-B, respectively). Does this mean anything to anyone? An internet search unsurprisingly didn't find anything. Any other ideas for finding aftermarket pistons? 2. Unless something turns up for (1), I'll probably just buy a new compressor unit with the money I'm getting back from the prior owner. To this end, I've been looking around and have found both 3hp and 5hp options--the latter generally being considerably more expensive. If the only difference between the two is air delivery levels (i.e. max PSI and max RPMs are otherwise the same), is there a reason the 3hp compressor couldn't/wouldn't/shouldn't be put to work connected to a 5hp motor? Thanks, -s


I have a 3 H.P. and a 5 H.P. same manufacturer. The pumps are identical. The only difference is that the motor pulley on the 5 horse is bigger and spins the pump faster to up the CFM.


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## Thurman (Feb 9, 2009)

"spavined"--IF looking for a new compressor unit, look to see what they are rated for as far as "max H.P" and "max R.P.M.". Then you can size accordingly to your motor. A rule of thumb we used with air compressors below 100 H.P. was: 43.8 (a factor #) X motor H.P.=Surface Feet per Minute (SFM) @ 90 P.S.I. discharge. An example: 5 HP x 3.8=app. 19 CFM @ 90 PSI discharge. This _all _depends on system piping, etc. Some of the units I worked on were 360 H.P., 1450 SFM @ 90 PSI. These were two-stage units with 10" high pressure, and 17" low pressure pistons. I really miss working on those larger units. BUT--I ain't un-retiring! David


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## junkcollector (Nov 25, 2007)

That pump rings a bell for me, looks like a 70's vintage Campbell Hausfeld. Try giving them a call once.


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