Air compressor

**tpilews** · 09-12-2007, 01:05 PM

Hi, I have a Craftsman air compressor that is not building pressure. It was working fine but noticed that it was leaking oil, so I took it apart to replace the seal. Put it back together, added oil, turned her on. It comes on, but does not build any pressure.

I checked the intake side of things to make sure the flaps were opening and closing, and everything looked alright. It does sound a little different that it normally does.

Sorry, this is a little vague. I'm hoping some of you might have some experience. I'm at a loss. I searched around google, and couldn't find anything worthwhile.

**Hot Black Trans-Am** · 09-12-2007, 01:57 PM

Did you check the air filter? I have a craftsman and mine leaks by the gauges/regulator area bad when I have the air pressure turned up. Maybe the bypass valve is stuck open. Do you hear air leaking anywhere?

**tpilews** · 09-12-2007, 03:19 PM

Originally Posted by Hot Black Trans-Am

Did you check the air filter? I have a craftsman and mine leaks by the gauges/regulator area bad when I have the air pressure turned up. Maybe the bypass valve is stuck open. Do you hear air leaking anywhere?

I dont' hear it leaking anywhere. When I put my hand near the intake filter, I do feel a little suction, but I also feel air coming out. I guess the intake valve could be staying open. Any other ideas? Thanks.

**Hot Black Trans-Am** · 09-12-2007, 03:24 PM

You can pull the output pipe and see if air is coming out there. When they are pumping into open air there isn't really much air that comes out of the motor so it won't be huge amounts like when there is pressure in that tank.

**tpilews** · 09-12-2007, 08:06 PM

Originally Posted by Hot Black Trans-Am

You can pull the output pipe and see if air is coming out there. When they are pumping into open air there isn't really much air that comes out of the motor so it won't be huge amounts like when there is pressure in that tank.

Figured it out. When I replaced the head gasket, I cleaned it up real good, and the gasket that was on there before was torn to shreds. Well, I only put gasket material around the outside, I forgot the part in the middle that separates the intake and exhaust flaps.

Thanks for your help though HBTA

**Hot Black Trans-Am** · 09-13-2007, 01:35 PM

Originally Posted by tpilews

Figured it out. When I replaced the head gasket, I cleaned it up real good, and the gasket that was on there before was torn to shreds. Well, I only put gasket material around the outside, I forgot the part in the middle that separates the intake and exhaust flaps.

Thanks for your help though HBTA

Glad to hear you got it working. It's easy to over look things at times.

**tpilews** · 09-14-2007, 08:40 AM

Originally Posted by Hot Black Trans-Am

Glad to hear you got it working. It's easy to over look things at times.

Well, I'm not sure if it is back to normal or not. It is building pressure, but it seems to be struggling to get over 90 psi in the tank. Also, it seems to be much hotter than before. I don't remember the tank ever getting warm, but now it is.

Well, it used to fill up in about 2 minutes. I let it run for about 3 minutes, and it was up to 90 psi.

It's a 30 gallon tank, 5 hp motor.

Am I just being paranoid?

When I first put everything back together, there was a small leak going from the compressor to the regulator, but I tightened everything down, and it went away.

Am I just nitpicking?

Thanks for your help.

**Hot Black Trans-Am** · 09-14-2007, 06:05 PM

Originally Posted by tpilews

Well, I'm not sure if it is back to normal or not. It is building pressure, but it seems to be struggling to get over 90 psi in the tank. Also, it seems to be much hotter than before. I don't remember the tank ever getting warm, but now it is.

Well, it used to fill up in about 2 minutes. I let it run for about 3 minutes, and it was up to 90 psi.

It's a 30 gallon tank, 5 hp motor.

Am I just being paranoid?

When I first put everything back together, there was a small leak going from the compressor to the regulator, but I tightened everything down, and it went away.

Am I just nitpicking?

Thanks for your help.

Your probably just watching it a bit to close. I have the same setup and I never timed mine to see how fast it gets up to pressure or ever felt it to see if it got warm or not. I know the last 20 or 30 psi takes the longest to build up though. If you don't hear any leaks I wouldn't really worry about it. Maybe seeing it's cooler out it might be taking a little longer?

**SpurSS** · 09-14-2007, 07:16 PM

Did you notice any coking around the reed valves? Coking is a deposit left behind when oil is burnt off. If you noted coking change the oil to a better oil, I use synthetic. If the valve seat or reed valve area has any scratches you will loss efficiency, and increase the temperature of the output air. A little air flowing back out of the intake is normal, while running. If the valve is hanging open, just a little, you will loss the higher pressure, notice a different sound while running, and the amount of air flowing out of the intake will increase. By the way when not running there should be no air leaking out of the intake, any air out indicates leaking valves. If this is the direct drive style of compressor, no belt, they make them some what disposable.
Good luck

**SpurSS** · 09-14-2007, 07:19 PM

By the way, over the last twenty five years I have operated and maintained compressors from 3 cfm to 1200 cfm, in recips, and screw configuration.

**tpilews** · 09-15-2007, 07:54 AM

Thanks for the replies, I think I may just be looking into it too much, but SpurSS did provide me with some great information, which I will definitely check. There is no leaking at all when it is off.

Is it okay to use motor oil as long as it is full synthetic, or is a compressor specific oil preferred?

Also, this is a belt driven craftsman compressor

**tpilews** · 09-15-2007, 07:58 AM

The valve plate itself does not have any coking, but the valves themselves had quite a bit. I sanded them down to get rid of it all. Is this acceptable, or would replacements be in order? They can't be but a couple bucks, so I'll probably end up changing them.

I just want to make sure it is running in tip top shape before I put the stress of running higher cfm tools on it.

**SpurSS** · 09-15-2007, 08:10 AM

Efficiency gains are slight if there is no air leaking out while off, if the ports are clean, if you can get new valve reeds go for it, try cleaning with WD40... or in a parts washer, if needed.

I use a match to look for air leaks, the flame is very sensitive to air movement, as well as the smoke when it goes out, say ouch

Any syn oil if fine, mine has 10w30, ya know the last 1/2 quart from the oil change.

**Sunset T/A** · 09-15-2007, 04:41 PM

Recommended oil for all compressors is NON-Detergent 30W. I buy mine at PepBoys. It's hard to find non detergent oil.

**tpilews** · 09-18-2007, 11:08 AM

Well, there is definitely a problem with it. It couldn't even keep up with an angle grinder that needs 4cfm at 90psi. This compressor is supposed to put out 10 cfm at 90. After it ran for about 4 minutes, I noticed it starting to smoke so I turned it off right away. Any suggestions.

Maybe I'll take her apart and get some pictures up. It might be easier to make a suggestion after that. I need to let it cool down for a bit though. So, pictures will be up later.

**tpilews** · 09-18-2007, 11:11 AM

Also, as far as non-detergent oils go, is it clearly stated on the packaging?

**tpilews** · 09-18-2007, 02:26 PM

Alright, got some pictures

Head

Valve plate

Crankcase

Closeup Crankcase

**tpilews** · 09-18-2007, 02:27 PM

Most of the crap in the cylinder looks like gasket material

**tpilews** · 09-18-2007, 02:28 PM

Any ideas??

At this point, I'm just thinking about replacing the head and valve plate assemblies. Including the valves and gaskets, it comes out to $124. I'm going to try to clean it up real good and change out the gaskets, see where that takes me.

**SpurSS** · 09-19-2007, 12:03 PM

Good pictures, it looks like you have a overheated valve (third picture, top valve) as indicated by the blue-black color of the strip. I notice a possible heat issue at the fitting where the discharge line goes into the tank(maybe just dirts or something). I would not replace the valve head(save the money), unless you have wire drawing at the interface between the valve and where it meets the head (that could cause the discoloration), but the reed valves have to come off to see. It looks like the head is pot metal and can be damaged by sharp edges such as a screw driver. Use something like a scotch pad to remove the gasket material. I know you said that you have had the head off before, did you replace the gasket or was it in better shape than it is now, if you replaced the head gasket the last time you need another new one, if you put it back together the lastime with the gasket in similar shape that could have been your problem, and it would have sounded different.
What I can see of the cylinder walls looks good, if the rings where gone you might see damage(groves) in the direction of the stroke. It look like it is worth repairing, I would try the valves first, cheap fix before the expensive one. Let me know if I can offer any more assistance.
John