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Discussion Starter · #1 ·
I have a 80 gallon Sanborn air compressor that is blowing hot air from one of the intake filters ( there are 3 pistons each with there own air filter) I was doing some sanding in the garage and I noticed it kept running and my pressure was a little low. It usually gets to 150lbs in under 5 minutes. But it was hovering around 100psi and had been running constantly when i moved my hand past the air cleaner housing and it was pumping out hot air at a pretty fair rate. The compressor is only 2 years old, and I did some light painting with it a year ago and i just run basic hand tools with it on a semi average basis. What gives ? Did a cylinder burn up?? The other two are sucking air and running cool, this cylinder is pretty hot. It has plenty of oil which I can see thru the sight glass and is fresh.
 

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Discussion Starter · #3 ·
I pulled the head, i'm assuming the Reed valves are the think flat metal pieces that go over the Ports .. There not broken everything looks clean, piston head looks ok. Cylinder wall still has good cross hatching...
 

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read valves

are they laying flat ?? u may want to pull them and clean with brk fluid.. thats really the only way u get air comming out of the intake area's cause the read's are fouled somehow...
 

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Discussion Starter · #5 ·
Well I pulled it all apart, everything looks great, reeds are flat and straight. Piston looks fine, cylinder wall looks good, still has nice crosshatch. Im sure the rings are good cause it pushes air out at a good rate. Im going to clean it all and put some new gaskets on it and hopefully it works....

When assembling these things should I use just some non detergent compressor oil to hold the upper reed in place?
 

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you may have just got a small piece of something under a reed valve. check to make sure it sits flat on the seat of the head. that is about the only way you can get air backfeeding through the inlet is through a leaky reed valve. the parts are pretty cheap for those, maybe just install a new reed and make sure the seat in the head is in good shape, no paint residue etc. then put it all back together (I use compressor oil on the reeds to hold them) and try it. should work. good luck.
 

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the 'Duracell Project'
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try to re-surface your head or reed valve block with 400 grit sand paper stuck to a flat surface.
i rebuilt one of our compressors that way
 

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Discussion Starter · #8 ·
Ive pulled it apart 4 times now and im ready to start pulling my hair out instead. I just cant figure this out. the reed valves are straight as an arrow and clean as a whistle. they are staying in place when i assemble the head. Ive tried all new gaskets. still blows air back out the intake. There is no physical way the valve are sticking or dirty. What could I be doing wrong?

I even "resurfaced" the head with some 400 grit and a hardblock. after that it still leaked so I took it all apart and reassembled with a thin layer of RTV and it still leaks. So I did a third time and cleaned off all the rtv, cleaned everything again. Leaks...
 

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Discussion Starter · #9 ·
Well I guess the 5th time is a charm, i got it working again. Still dont know what went wrong I guess a reed valve had to of slipped out of place when I was putting the head back on. I think I could assemble one of these in my sleep now, haha. Thanks for the help everyone
 
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