Air compressor never goes above 50psi - just levels off and keeps running...

I recently got a small (1.5 HP, 2gal) Craftsman air compressor which seems to work fine with one exception:
It never gets above 50psi.
Now, it doesn't shut off at 50psi. The motor keeps running and running (it's supposed to cut off at 125psi). It doesn't seem to strain at all and I can't detect any leaks. Also odd is the fact that it gets up to 50psi quickly and just stays at that pressure. It's not like it seems to be having a hard time getting there. The pressure just immediately levels off as if a valve opened. However I can't detect any air escaping at 50psi.
If I shut off the compressor it holds 50psi indefinitely. No leakage at all.
Any ideas? Why would this compressor just STOP? Is there something I should know that I'm missing?
I don't know if I can take it back (it's used). I just want to know if there's a setting or valve which can account for this.
Please advise.
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Generally, this is not good news. It usually means that the compressor has become inefficient due to an internal mechanical problem or excessive wear. There's just too much internal compression loss to come up to the full output and it just plateaus once the resistance reaches a certain point (50 psi in this case). The fact that the tank holds the pressure without loss only tells you that the check valve is working and doesn't tell you anything about the condition of the compressor. If you're mechanically inclined or adventurish, the next step would be to remove the head of the compressor and visually inspect inside it. You can usually see when things are obviously amiss.
D.

there's
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pls replace nospam with my name to reply privately.

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Thanks for the input.
It's odd about the wear, considering this compressor looks almost brand new as I got it. Also, it goes up quickly to 50psi and levels off suddenly; it doesn't look like it's struggling to get to 50.
I may have an opportunity to swap it out; I'll see. Otherise I'll pop the head.
Is there any gasket sealant or anything I would need to reassemble the head?
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Had a similar problem. One of the bolts on the head was sheared off. Ordered another one from Sears parts ($.90) + $3 shipping, and replaced it.
The compressor itself is very simple if you have the oilless ones. Just a piston w/ teflon rings inside a cylinder and w/ a head that has an intake and exhaust valve. If you're even remotely mechanically inclined and a methodical thinker you can probably diagnose and fix it yourself.
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This is an oil lube compressor; still, however, it seems reasonably simple, mechanically.
I'm confident with opening it up; I was just curious, before I did, if there was any knowledge about this kind of problem.
Thanks!

it.
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Thanks. So this sounds like a known problem, eh?

adjustable
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On Sat, 26 Jul 2003 22:10:42 -0400, "Stellijer"

possabley a faulty presure gauge ? test for this is to hook up another presure gauge and see if it read 50PSI also
nother idea is to take back to sears and say that your wife or bro In law got it for you as a gift ansd you don't have the receit and try to exchange it or get Sears to repair it
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