I have a 2004.5 S40, the brake vacuum pump has been buzzing loudly since I bought it 2 years ago. It starts whenever I stick the key in (car not running yet), and it won't stop buzzing after I shut off the engine, it will continue for another 5-10 minutes.
Another issue is the pump is EXTREMELY hot, even after running for only a short while.
Is that normal? I've been to 2 mechanics but can't find out what's wrong. (IMG:style_emoticons/default/sad.gif)
One of the mechanics replaced relay and the pump, but nothing happened.

thanks!

 

If it runs contantly, unplug it, for now. Where it has a hose connected to it, it runs from there to a couple places but ends up at the left of the battery, then connects to another hose, correct? This other hose is more than likely your problem, you may have to remove the battery tray to replace it, but it has a switch for this pump to activate it. TRY THAT and LET ME KNOW.