Hmmm...I'm not buying that the caliper's making noise. I'd guess that your parking brake is adjusted too loosely, and that's what is knocking around back there. Had this happen on my 500E. Adjusted the P brake; noise gone!

Good luck!

__________________
"If God had meant for us to walk, why did he give us feet that fit car pedals?" Sir Sterling Moss

Michael
2014 E63S Estate
2006 SLK55
1995 E500
1986 Porsche 944 turbo