Swan 40gallon air compressor pump HELP!!!

[mr.jake]

Hi all, i've been lurking with forum for the past 6 years reading all the interesting discussions. Now i finally have a question to ask. I have a swan twin cylinder, single stage air compressor. It has a 40gallon tank and 5hp motor. Since i got it (second hand) the one cylinder wasn't nearly as strong as the other. It got to a point where under load the cylinder now blows air out the intake of the weak cylinder. This unit has a metal valve assembly with intake and exhaust metal disc and spring "check valves" (not sure if thats a good description) The valve assembly sits inside the head and head gasket blocks intake from exhaust ports. I checked the gasket and wasn't blown out. I have removed the valve assembly and disassembled/cleaned. It was full of crud so figured the intake valve was held open. Re-assembled it and made a head gasket for it. Still blows air out of the intake when it hits around 30psi. I removed the valve assembly again and trued it on my southbend lathe. Checked flatness of the valve plate to the discs, all looks good. Re assembled and same thing. The gasket has a heavy indentation indicating it is sealing around the intake portion of the valve plate.

i fear soon ill have no hair left on my head after trying to get this compressor to work. Its starting to drive me nuts. Any help would be very much appreciated. I can upload some pics of the parts im talking about if its of value. Hoping come compressor guru will chime in and tell me im an idiot and get this thing pumping! Thanks for reading!!

 

[jrsulo]

You look at the in tank check valve yet ??

 

[mr.jake]

no, but it doesn't leak when shut off so i assume its not the problem. Also only the one cylinder is leaking.

 

[jrsulo]

When I pulled mine apart it was one problem after another,,,,fix one thing find another problem,,,,came close to giving up,,,,so glad I didn't !!!!

 

[mr.jake]

hahaha i know the EXACT feeling!!! I keep thinking it has to be something simple and i'm overlooking something, but everything seems to be in order and should work. I'm stumped!

 

[jrsulo]

Just keep at it and don't lose your cool !!!!!

 

[G_P]

Is it possible that there is a crack in the head or in the piston?

 

[mr.jake]

I have checked the head for cracks, nothing that stands out but ill check again. I don't think the piston could have anything to do with air coming out the intake as the intake valve should prevent compression from escaping through the intake port.

 

[MacMcMacmac]

Do you have copper crush rings under the valve bodies? Is the cap for the valve seating the valve to the head? If both are true, and the gasket is properly crushed, the only other thing I can think of is that the valve itself is leaking back. I chased a leak like that on a Quincy once. Everything looked great until I ran the pump for a bit and it would begin popping back through the intake filter. Turns out, the valve body was worn to the point where the disc could seat off-center, creating a crescent moon shaped gap around part of the outer edge of the disc when seated. A new valve body solved that problem.

 

[mr.jake]

Do you have copper crush rings under the valve bodies? Is the cap for the valve seating the valve to the head? If both are true, and the gasket is properly crushed, the only other thing I can think of is that the valve itself is leaking back. I chased a leak like that on a Quincy once. Everything looked great until I ran the pump for a bit and it would begin popping back through the intake filter. Turns out, the valve body was worn to the point where the disc could seat off-center, creating a crescent moon shaped gap around part of the outer edge of the disc when seated. A new valve body solved that problem.

The valve assembly for the worn cylinder was .027" thinner than the good side valve assembly. I took shims and shimmed it .027"" under the valve to bring it up flush with the cylinder head. I used some anaerobic loctite sealant around the valve to seal it as the crush ring was now under the shims. Ill be going out soon to tinker with it and report back.

 

[mr.jake]

So i got tinkering again tonight, i shaved the cylinder head down about .030" until flat, the intake section of the head was cupped inwards. Installed the valve assembly with anaerobic sealant to insure no air was getting around the valve plate. Made yet another gasket and assembled everything. Starting off all seemed well, great suction from both intake ports. around 50psi the bad cylinder intake suction started dropping. 55-70 air was blowing out the intake. WTF!!

So question, this is a V style twin cylinder single stage compressor. The good cylinder is Teed into the bad cylinder, from there directly to the tank. Is it possible that the air pressure from the good cylinder is causing the bad cylinder valves to blow open or is there supposed to be a check valve from the bad cylinder to prevent the air from the adjacent cylinder from entering the bad cylinder? Is it possible the valve arrangement is different between the cylinders, in that air from the good cylinder enters the bad cylinder on the compression stroke, then the bad cylinder forces air from both to the tank? I'm just throwing ideas out there as i'm out of ideas other then try and find a new valve assembly, if possible!? Here's a pic of the pump, next tear down ill snap some of the valve assembly. Note discoloration of left cylinder!!

 

[ger]

I have a Swan compressor SVU 203 circa 1985 that has had the air controls removed. Could you provide me with a picture of your controls and location of each so I could set mine up properly. Thanks. Not much info around on these compressors, so need some help on this.

 

[mr.jake]

Are you talking about the pressure switch setup?

 

[ger]

All the new pressure regulator switches have a relief line (1/4 ") that is installed in front of the one way valve. My compressor does not have a place for that line in its original set up. I need to know if anyone has a picture of their setup (original) to know what I need to have on mine. Thanks

 

[redmondjp]

All the new pressure regulator switches have a relief line (1/4 ") that is installed in front of the one way valve. My compressor does not have a place for that line in its original set up. I need to know if anyone has a picture of their setup (original) to know what I need to have on mine. Thanks

That 1/4" line is for the unloader. Does your compressor have an unloader already? It might - check for a small orifice upsteam of the check valve. Yes, it's a by-design pinhole leak in your pressure line between the pump and the check valve. Many older, smaller compressors used this type of unloader. If you have this type already, then you do not need to connect the unloader valve in your control box to anything.