25 gal horizontal craftsman air compressor is leaking at the pressure control valve. Can I replace the valve or repair it?

Some pressure switches have a valve that reliefs the compressor head pressure when the motor stops and closes the head pressure relief valve when the motor runs.
There is a check valve that keeps air pressure from coming back to the compressor head and the relief valve.
I think the check valve is leaking tank pressure to the relief valve and compressor head.
The check valve is where the pressure switch mounts on to and it mounts threaded on to the compressor tank.
Try replacing the check valve

i would look at the head gasket

Sounds like the reed valves in the head failed. you need to replace the head (usually cheaper to get a new compressor)

if they are oilless compressors then the rings are worn

Check the pressure release valve to make sure it is not leaking. Do a compression test if necessary and check gaskets for leaks.

The compressor will not auto shut off until it reaches the preset pressure which is usually around 100-130 psi - your problem is leakage of air from the oil filler cap suggesting that you have a failed internal valve.

ONLY TWO THINGS CAUSE THIS, A DEFECTIVE PRESSURE CONTROL VALVE OR A WORN OUT COMPRESSOR, THIS ASSUMES YOU HAVE NO LEAKS.

compresors pump, valvs or sels gon!

compressor will not build pressure

start your compressor and let it buid up pressure to turn off. then unplug from power.lossen the fill tube that goes from the pump to the tank. when you loosen it. if it leaks air then your check valve is bad and will have to be replaced.