Inspecting a Vintage Air Compressor (Checklist Recommendations Please)

[7th Kahuna]

Is there a check list of sorts for evaluating an older (rough guess 1950's) air compressor?

A couple days ago, I went to look at another tool and literally bumped into an air compressor. It is a horizontal compressor with a flywheel and is probably sitting on a sixty gallon tank. Made in Los Angeles. I didn't look too close, even for a name, except to note that it was 3hp and single phase. I didn't even look to see if it had a cord (it's on four castors). The previous owner passed away recently and its condition is unknown. The son has no idea when or if his father last used it. It has been sitting outdoors in the California sun for an unknown number of years. It doesn't look like a lost cause, but to me vintage tools rarely do . The truly bad news is that it has been on my mind ever since. Eventually I need to do some media blasting.

After reading through several threads here, i feel a lot more confident about the unknown condition of the tank, but I'm still left with questions.

Assuming one is not a compressor junkie, is it generally worthwhile to pick up an untested vintage compressor for more than scrap metal value? What is the risk of it being completely dead?

Vintage motors in my experience tend to run pretty consistently, do old compressor pumps do likewise or am I much more likely to be getting a crash course in pistons, gaskets and pressure switches? My guess is people are more likely to write about the ones that didn't work when they got them home than the ones that did. I'm not against rebuilding it, but now may not be the best time for another project.

If it hasn't been run in years, is it safe to fire it up without giving it a good going over. Can you achieve a meaningful test without pressurizing the tank and stressing the pump?

I've talked myself into at least going back and taking another look. I will try to open the drain, hand spin the flywheel, and get some pictures. What else should I be looking for?

I thank you for your shared experience.

 

[Roberts210]

Can you turn the compressor over by hand? They're kinda like car engines--if you can turn them over by hand, generally they can be rebuilt, but since there's no combustion by-products in the compression chamber, compressors are cleaner inside and last longer.

Definitely open the drain and see what comes out. As long as the motor hasn't been burned up internally you can always put new bearings in it and revive it.

 

[redmondjp]

Check oil level in pump. If there is any oil, does it look like clean car motor oil, or like a mocha (water in oil emulsion)?

Check tank drain for water and oil, a little bit of either is OK, but the less oil, the better.

Do reading on this site about hydrotesting the tank - there are plenty of threads on it.

Do you enjoy rebuilding compressors in your spare time? Or would you rather use the compressor to rebuild or fix something else? Only you can answer this question.

A compressor of that vintage, assuming that the pump hasn't been changed out, can have parts that are still available or are completely unobtainium. If you get some nameplate data and pictures we can help you figure that part out.

 

[Boilerhouse]

I see more downsides than upsides. Sitting outside, history unknown, condition unclear. Its a coin toss if this is ultimately a good machine or not. I would probably low ball the offer to limit any losses.

 

[kenfain]

I see more downsides than upsides. Sitting outside, history unknown, condition unclear. Its a coin toss if this is ultimately a good machine or not. I would probably low ball the offer to limit any losses.

I concur. Why not snap a couple pictures, put it on the forum. Some of these things aren't worth the trouble to fix. Just because it's old, doesn't mean it's valuable. Otoh, it could be a name brand, that just needs some tlc. There's a lot of knowledgeable folks here. Better to be fully aware of the value, going into a thing like this.

 

[Roberts210]

On the other hand, this guy is from L.A. where it hardly ever rains. Maybe the compressor doesn't have a lot of rust. At least go take another look.

 

[md21722]

Old tanks or newer tanks may or may not have rust and need to be scrapped. I have seen 60 year old tanks with less internal rust than 8 year old tanks. Does it have an air filter? If it turns over by hand you might remove the discharge hose (from compressor to tank) and see if its go heavy oil or carbon deposits. If the pump was blowing oil then it would be coated pretty thick. Should be no more than a light carbon coating. If it was sitting outside sometimes the valves can get rusty and any springs can break (if disc). The rest is often basic parts, like pressure switch and blowoff valve that should be easily replaceable if not working.

 

[7th Kahuna]

Thanks everyone for the input. Yes I would rather be using it than fixing it but there is a sense of pride (and perhaps a good story) to be found in a little fixing.

On the other hand, this guy is from L.A. where it hardly ever rains. Maybe the compressor doesn't have a lot of rust. At least go take another look.

Yes, that was why I mentioned California sun. It is sitting on a concrete pad, in the open, no bushes or trees dropping leaves into the nooks and crannies, no sprinkler over spray. The motor tag had so much dust on it I couldn't read it. Now there could be a lot more rust than I think, I only checked the motor tag because I wanted to know if this equipment had come out of a three phase shop. I seriously had no intention of possibly bringing home a compressor.

So I am going to give the guy a call and see if I can take another look and take some pictures. I let you all know what I find out.