06 Scion tc squeak/rattle front end when cold at idle?

I have an 06 tc and I've been having a problem with a noise for the past 3 winters. It only happens when the temperature outside is cold (below 35 degrees). It's a squeaky rattling noise coming from the front of the car. It only happens when in gear (Drive or Reverse) and idling (with foot on brake). It doesn't happen during acceleration or while driving. The dealership replaced the serpentine belt, but the noise is still there....driving me crazy....any ideas?