Compressor repair

[jviss]

I would appreciate some input on my garage compressor.

 

I have a Sears 5 HP, 20 gal. compressor, model 19.176850. It's about 25 years old. It has seen regular, light use. A lot of that use has been pumping back up from cut-in to cut-out pressure due to a tiny leak in my garage air plumbing, when left on.

 

It's not pumping well now, and I think it was damaged due to overheating. Here's what I think happened:

 

For some reason there's a lot of oil on everything; I don't know why. The pressure switch was pretty oily. Don't know if this is what initially caused the problem, though.

 

The pressure switch failed. The compressor came on, and ran past the switch cut-out pressure of 125 psi, until the overpressure relief popped, and then just kept running. I don't know how long it ran. My wife found it; the garage was hot and smelled bad. She shut off the compressor breaker at the electrical panel (good girl!).

 

Everything was oily. The switch won't cut out, and now, the compressor pumps up, only very slowly, There's some air pumping back out of the intake, and I can detect an air leak at the head gasket.

 

I drained the oil, and got only about 3 ounces. Should have been 16. I had changed the oil about a year previous. Refilled, but it's leaking from somewhere.

 

Check valve is O.K.

 

So, I'm planning on pulling the head. While I'm at it I may just remove the pump from the rest of the assembly and look for a crack, or whatever, that would explain the oil leak.

 

This compressor uses flapper valves.

 

So, does anyone have any experience or insight on these things? I'm tempted to attempt to repair the pressure switch, 'though they are pretty cheap to replace. Any suspicion I may have a ruined cylinder and piston/rings?

 

It isn't making any bad noises. It just takes forever to get to 125 psi ('though it does get to 125).

 

So disappointed! I considered replacing it, but the 'economy' Chinese compressors get such bad reviews, and otherwise a compressor this size is a lot of money.

 

Any help or advice appreciated.

[enfoman]

Sounds as if the reed valves for your compressor have given up the ghost due to age and use. (of course the incident did not help) Good thing the relief valve popped instead of the tank. I make it a point to shut off the compressor after every job. Bad things like yours or worse can happen and there is really no discernible immediate need to have a ready standby air supply at home. If you can find them, Change out the reed valves and flush, change the oil and replace the regulator if you think it is worth your time,effort and skill set. Otherwise, consider something new.

[Richard_D]

http://boston.craigslist.org/nos/tls/2740999475.html http://boston.craigslist.org/nwb/tls/2754679735.html Try here. http://www.searchtempest.com/

[ESokoloff]

First the disclosures...

Not familiar with your unit.

I'm not an air compressor expert tho I know more about them then most

 

You said that the head gasket is leaking so an open & inspect sounds to be in order.

I would try to find a rebuild kit & pull the top end off.

 

No abnormal noises so if the cylinder wall(s) look good it might indicate the rings are not worn & the bottom end is OK. (I'm not an expert tho).

 

The loss of performance may be in the valves and you may find them to be weak.

They should be reed valves which operate on pressure differential.

Open on negative & close on positive.

You MIGHT be able to test the seal by pouring a liquid

on one side of them & watch for escaping fluid from the other side.

 

The oil on/in the control (P.E. pneumatic/electric)switch may indicate a leak.

A typical PE switch also incorporates a small valve that opens & relieves the discharge pressure when the PE opens.

If this valve were to leak that may account for some performance loss as well as explain the oil accumulation.

Not sure why yours failed.

If the contacts welded you may have another issue as well.

I cant remember seeing one fail mechanically but you said yours was subjected to elevated cycles.

Probably best to just replace.

 

Hope some of this helps & good luck.

 

 

Sooo when's the next air compressor Tech Daze

 

 

 

[AviP]

I wouldn't replace your compressor until it's terminal. They don't build them like they used too. Pull the head and check the gasket. If they don't make a rebuild kit, make your own gasket.

 

It's good that there's a leak at the gasket because that may have saved the piston rings. Let us know how it pans out.

[ESokoloff]

They should be reed valves which operate on pressure differential.

Open on negative & close on positive.

 

 

That would only apply on the suction side.

 

Discharge would be the opposite

[jviss]

It looks like I can get any of the parts I need: valve kit, gaskets, piston, rings, etc. I guess it just remains to pull the head and see what's going on.

 

Found a pressure switch that looks identical to the original on eBay for $15 (Sears wants $57).

 

 

[ESokoloff]

Make sure that switch can handle the 5 HP motor.

 

May want to tear into it before ordering parts.

 

Out of curiosity how much to rebuild the top end or better still a link to a parts list?

[jviss]

Link to the parts list;

Compressor parts

 

 

[jviss]

May want to tear into it before ordering parts.

 

Agreed. Going to pull it apart first and see what I'm dealing with. Curious about the oil leak.

[ESokoloff]

Also on the switch, does the original have a bleed down valve.

If so, I'll state the obvious.. make sure the replacement one has one as well.

 

Not a deal breaker but does the original have a manual switch?

 

It's obvious that you can do better on price then Sears but make sure it's spec'd to do the job.

[jviss]

I'm not familiar with how the pressure switch operates. There appears to be two pressure connections, one from the bottom, where it mounts to the tank, and another, that connects to a small diameter pipe that connects to the cylinder head, and is labeled "pressure release pipe" in the schematic.

 

The one I found on ebay appears identical to the one I have, at least judging by the pics.

 

 

[ESokoloff]

As to the loss of oil..

I don't know enough to make much more then a guess.

It's splash lubrication so no oil pump.

Perhaps the ring(s) are weak & allowing oil to get sucked into the cylinder???

What does the fluid look like that comes out of the condensate drain on the bottom of the tank?

I would think excessive oil MIGHT indicate time for new rings.

[ESokoloff]

OK sounds like it will work on the plumbing side but that 5 hp motor

(current rating requirement) may be the deal breaker on the electrical side.

 

On the switch, the bottom connection is the input from the tank(pressure) and the side one is the discharge pressure relieve valve.

This relieves the pressure between the compressor discharge valves & the check valve that's located on the discharge lint to the tank connection.

The check valve prevents the tank pressure from leaking out via the valve in the switch & or out past the discharge valves in the compressor in the off mode.

[jviss]

As to the loss of oil..

I don't know enough to make much more then a guess.

It's splash lubrication so no oil pump.

Perhaps the ring(s) are weak & allowing oil to get sucked into the cylinder???

What does the fluid look like that comes out of the condensate drain on the bottom of the tank?

I would think excessive oil MIGHT indicate time for new rings.

The tank discharge was very oily, rust colored water.

[ESokoloff]

The rust is no indication on the compressors condition but obviously the oil is.

Do you know if the amount is abnormal compared to the past?

 

Sounds like it might be time for new rings.

(I'll bet their cheep enough).

You'll also need a tool to compress the new rings when you reassemble the pistons.

You'll need a hone too.

 

Hopefully someone else will chime in to confirm or correct me.

 

As far as the rust, air holds a certain amount of moisture.

The more you use the compressor, the more moisture is introduced into the tank.

Once inside the tank, a certain amount of this moisture condenses & settles to the bottom of the tank.

Its important to remove this moisture on a routine basses to prevent the tank from rusting out.

[jviss]

It was a lot more oil thank normal. I drain the tank periodically.

 

I guess the rings may be shot. I have a hone, and a ring compressor (I've rebuilt a few motors).

 

 

[ESokoloff]

 

I guess the rings may be shot.

 

 

A restricted air filter will also increase oil consumption.

[jviss]

I thought about that. The input filer it just a brick of felt. It could be clogged.

[jviss]

Finally removed the head and valve plate. Both the gaskets tore. The cylinders look great, no scoring, can still see the honing cross-hatch pattern. Valves, which are reed and should be flat, are discolored and a bit warped. I'll just be ordering a valve kit and gaskets, plus replacing the pressure switch which is what I think caused the problem to start with.

 

Any recommendations on how to soften up the old gaskets for more easy removal? The surfaces are all aluminum, and I'm concerned with potentially damaging the while scraping the gaskets off.

 

Thanks,

 

jv

 

[ESokoloff]

I Googled it and well, you could use

(note: some strong language), but you need an air compressor

But seriously, you could also use an electric drill.

 

 

Weak valves explain the sluggish performance (extended run time) but not the oil consumption.

How hard will it be to check on the rings?

If they have baked on oil that would prevent them from sealing properly.

Do you think the air filter was dirty?

 

I'm still thinking one or the other or perhaps both are the cause of the excess oil consumption.

[jviss]

Ho would you remove baked-on oil? The cylinders and pistons are yellow with baked-on oil. I can only assume the rings are the same.

 

The air input filter doesn't look bad, but it's the original, felt filter.

 

As I said, the cylinders aren't scored, or even worn much.

 

I guess I could install new rings easily enough.

[ESokoloff]

If the piston ring groves aren't impacted with oil & the ring gaps aren't excessive I guess your good to go.

Hard to see on this end of the keyboard.

 

As far as the filter, you could clean it using dish soap & squeezing, rinsing & repeating as needed.