Because BMW have fitted SAC to most of their models since about 2000, it's the SAC that death-rattles right before the clutch gives out when the pedal is pressed to the floor whilst stationary, and is the reason that you won't know your clutch is trashed until you get the odeur de brûlé .
An example is featured here on BMW TIS http://tis.spaghetticoder.org/s/view.pl?1/06/39/51
Yeah I think I need a new one as well. I just can't find a place that sells one that will fit my car. A lot I seen way they fit production date 10/03 thru but my car was made on 10/02