The car has about 145K miles on it. The brakes seem to be functioning normally.
Often when I shut off the engine I hear a buzzing noise every 10 seconds or so coming from the vac. brake switch. If I un-plug the electrical connector it stops buzzing.

What is causing the valve to buzz after the ignition is shut off?
Thanks,
Art

What you’re probably hearing is the auxiliary vacuum pump that is supposed to maintain vacuum in the brake booster line for a certain period of time after the car is shut off or during times that the intake vacuum is low. If the brake booster or it’s vacuum line leak air, or if you press on the brake pedal after the engine is shut off, it will call for the pump to run momentarily and repeatedly depending upon how fast the vacuum was depleted.

To test if the leakage is within the booster you can disconnect and plug its vacuum line. Then run the engine for several seconds and shut it off. Does it then take longer before you hear the pump buzz? If so then the booster very likely has a leak. Now we can have a discussion as to whether the pump running every ten seconds is excessive or can you wait until it gets worse before you worry about fixing it.....

I will check further per your guidance, Thanks.
Art