Engine Noise 2003 S80
 

Hi, I have a 2003 S80 2.9.
After the car is shut off, there is a buzzing sound that comes out of the engine every 20 seconds or so for a few minutes then stops. I traced it to a round silver gizzmo just to the right of the radiator and a bit lower. It has a few hoses that come out of it and an electrical connection. When I disconnect it electrically it stops and resumes when I plug it back in.Any idea what it is and what it does? Can I change it myself? Thanks

Sounds like maybe the brake vacuum pump.
Anyway you can post a pic of it?