I have a old Sears air compressor made in 1968 it has about a 40 gal tank and a twin piston pump with a centrifugal unloader on it. What it is doing is at about 100 psi it starts to labor and spit air out the filter nut on the centrifugal unloader. It always would run up to 150 psi and shut off without any problem. Does anyone know what would cause this problem?????

Thanks

Rangr90