Is my compressor shot?

Also, it looks like a single stage 2 cylinder pump. Has reed valves in the head that lets air in on the down stroke, then closes and pushes the air to route to the tank on the upstroke.

Those reed valves can break off one of the flex tabs, then the pump does not work very effectively, over working it, heating everything up, and tripping breakers.

Easy job to pull the head, and check the reed valves. If you are careful you can probably save the head gasket too.

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That check valve at the tank is a big suspect too. Suposed to be a check valve with a bleed off. Holds pressure in the tank and bleeds pressure off the line and head so it is easy to spin up on the next restart. Not having to pump against the pressure in the tank.

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Also you could drop the cut off pressure down to 110 lbs instead of the higher 135 psi. That will lighten the load a lot on your well used compressor, helping to extend it's life.