Hy smokinjoe3 and guys, If you are hearing noises in the cab with the engine off and while stepping on the brake pedal you are hearing the atmosphere valve on the Hydrovac opening to allow air at atmospheric pressure to enter the apply side of the Hydrovac. Air under atmospheric pressure on one side of the bulkhead/diaphragm air under a vacuum on the opposite side of the bulkhead/diaphragm the shaft connected to the bulkhead/diaphragm will move more easily toward the side under vacuum. So your booster seems to be at least partially working, but you are not able to feel the effect so something in the system must be frozen or seized. A complete inspection and repair of the braking system should reveal the problem.
