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My air compressor does not reach full pressure. What parts do I need to replace to fix it?

Sears Craftsman Permanently Lubricated Air Compressor; Model 919.155731; 3.5 HP 25 Gal tank; purchased 10/92; The compressor runs well but it peaks at about 50 psia.and last year it went to 100+ psia. The air filter is missing, but everything else is as it should be. I do not hear any air leaks when the motor is not running, yet it will slowly lose the 50 psia over time. I have the parts list and the exploded view. It appears that the means of compression is an 'O' ring on the head of the piston. If I replace that plus the gaskets, will it resume its function? Is there something else I should do?

Air Compressors , Craftsman
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2 Answers from these members:
Joey S
Running the compressor without a filter can cause a failure within the valve plate assembly. I can't be certain of your failure but the valve plate assembly is no longer available. Replacing just the o-ring may not resolve your problem. If you do replace the 0-ring be sure to replace the head gasket too.
by Joey S Earned 8,558 community points in Craftsman
April 28th, 2010
0 votes
Manage My Life
This compressor seams to have a problem with the reed valves. They are not available from Sears.
I have tried to find them ,but, no luck so far. If anyone knows where to find them please let me know.
Thank you, Dale
by Manage My Life
November 22nd, 2010
0 votes
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