hey whats up guys...i've got a 2000 B5 1.8, i don't have any problems with it, i just hear a peculiar sound sometimes when i start it and when i get to the end of my street or around the corner and come to the first complete stop i hear this sound like an electric motor. it turns on for a couple seconds and then turns off. nothing noticable happens but i was wondering what the sound might be? thanks guys

 

Its probably the vaccum motor for the brake booster.

 

The noise you are hearing is most likley your secondary air pump. This pump is activated to warm up the cats, for faster catalyst efficiancy. This pump is only run when the
engine is cold. I assume this noise is loud considering you have not noticed it before, so you might have a leak at or near the pump. If this is the case a check engine light
will soon follow.