Originally Posted by PichaDis11
Slight revision changes is the best guest. Thermostats were all aluminum housing before cars up to 08 I think. Now it looks like plastic or it is. But BMW does change p/n ever so often so we may never know what happened. Would be glad to know those info as well.
I think I got my answer from the local WI Bimmer community forum that I visit. A member suggested that I check out penskeparts.com or realoem.com and this is a summary of what I found:
Description: RMFD WATER PUMP (to 06/06)
No longer available since 2007-02
Superceded by 11517563183
Description: RMFD WATER PUMP (to 07/08)
No longer available since 2008-04
Superceded by 11517586925
#11517586925 - Currently available
Description: REPLACE COOLANT PUMP, ELECTRIC
Interestingly, this water pump part # is 0.02 lbs heavier than the previous two. No idea what that might actually mean.
realoem.com link http://www.realoem.com/bmw/showparts...=11&fg=35&hl=5
penskeparts.com link: http://www.penskeparts.com/DiagramsM...ts=11517546994
My belief would be that if Penske Parts lists the part as "no longer available" and could not sell it, I would hope that BMW stopped using those part numbers in manufacturing by the dates they were no longer available, if not sooner.
So my theory
is that if your car was built after 07/08 and has a non-turbo I6 (N51/N52), you should have the latest water pump part # installed in your car.
I HOPE this provides some peace of mind for some of you out there! It's unfortunately just a theory and I have no real way of confirming if it's 100% true right now. I don't know for sure either if BMW really made improvements between the part # revisions, though I would hope they did.