We had a snap ring break which let the fan hit the housing on a 92 R62 several years ago and found that coupler area packed full of gunk just like a centrifugal filter. Our dealer didn't think the crud had anything to do with the snap ring failure, but after being down for several days waiting for parts and spending mucho buck$, I would have had that area inspected regularly had we kept the machine much longer. Happened at around 1400 engine hours.