One day I was driving to work and started my car. Well my ac is always on because I always use it. I turned my car on and heard the rattling before it actually started so I tried starting it and it started fine and ran fine all the way to work didn't act funny on the highway and whatnot. Except for that rattling. Couldn't figure it out until I got to work shut the car off and kept the keys in 2nd tier to keep the AC on. Since I still heard the rattling I checked under the hood. Sure as hell it was coming from the front only when the AC was on
Loud bearing noise especially noticed at high idle. I initially greased (white) bearing, but eventually will replace idler pulley.
Had a bearing squeal. Listened to noise and traced it to idler for A/C. remove and replace pulley. growl/high pitched wine is gone.