When the car is turned off there is a buzzing sound coming from under the air filter box l.h. side of car. Is it a Brake Booster Switch? how to check if it is working? it has been happening for a year now and does not seam to affect the brakes. Has anyone experience this?

here is the youtube video: http://www.youtube.com/watch?v=2htm0PBv_4E

 

Vac pump. No worries. Its the Vac for the break assist for the break booster. Mine runs for a min or so even when the car is off. Nothing to worry about. It normal. The pump is located right below the Airbox.Its a silver looking beer can size.

 

there are 3 noises in my volvo
the vac under the brake boost (normal)
the cooling fan inside the computer control moduel housing (pulls air into the box from the cab aria to cool the computers pretty neat if you ask me) and the little tiny fan behind the climate control temp sensor

this car is cool

 

It turned out to be the brake booster. I put a used one in last October.
I wanted to confirm for anyone with similar simptoms as it seams to be a common problem with Volvos.

 

I'm having that issue now. I think it was always there, but very mild. Now its pretty loud. Any suggestions on where to purchase the brake booster and/or any installation advice?