A buzzing solenoid can result from a loose solenoid bracket, worn solenoid sleeve, damaged/worrn solenoid plunger, worn coil stop, loose coil stop or loose coil stop bracket. Since the original coil stop gets the most abuse, it should be the first item replaced on a buzzing solenoid unit. To find the source of the buzzing, you can always switch out parts from another solenoid unit on the machine to see if it will quiet down the buzzing sound on the solenoid unit in question.