Question: On my 540i 2001 6 spd, I notice a pulley on the serp. belt between the Alt and PS pump. This pulley is without grooves and rides gently on the back on the serp belt. ? what is purpose here ? Seems like a strange place for a idler pulley as the length of serp belt run is rather short compared to other pulley to pulley distances on the same belt or even the AC belt. Almost no deflection of the belt with the pulley tension, so the exact reason is not clear to me. ? Any thoughts on this mystery ? thanks
You must be talking about part #11287500560 at http://www.realoem.com/bmw/showparts.do?model=DN53&mospid=47588&btnr=11_2012&hg=11&fg=18. Early models didn't have it (look at http://www.realoem.com/bmw/showparts.do?model=DN53&mospid=47588&btnr=11_1529&hg=11&fg=18 for comparison). Best guess is to dampen the belt vibration - the run is too long.
You are right ON!! That is the one. I have seen a similar diagram wo the ID numbers. Good work!! I have orderd some pulleys from Rock Auto that are supposed to fit the 70mm deflection pulley on the serp belts, but I notice from this diagram that the pulley in question is 80mm. I will be measuring them and making sure. Have 86k miles on the car and figure the last owner prob did not change out the pulleys. Just a preventative maintenance sort of thing... thanks again for the help. really appreciate it. Cheers
