What the heck is this???
 

Hi, so my X5 has a front end rattle over rough surfaces. It doesn't seem to be the standard clunk over a speed bump from a broken link. Smooth surfaces no rattle. Panels seem ok. Tonight I jacked up, wheel, carrier, rotor, etc all seem good nothing loose. I was banging on an under panel and I heard something loose. so I took a few screws off and banged on the bottom panel. A air intake clip fell out and this thing fell out... what is this. I've never seen this.

I think I just answered it, part of idler pulley. Years ago, my belt fell off because a pulley broke. I guess this piece fell down below the engine. Car was repaired,. new belt on. So I guess this isn't the cause of my rattle. I think my front suspension is due to refresh.

Wow. It's first time I've seen a cracked pulley. Usually the bearings wear out first. My guess it as a simultaneous failure. I've found sockets, clips, bolts, and other stuff on dust shields. It's nice to have a tool "catch can". PIA when you need to get a socket or tool you are using at the time.