I found information that non-turbo E9x cars used three different part #s for water pumps:

#11517546994
#11517563183

#11517586925

I didn't bother looking at water pumps for the N54/N55 becuase it's already been established that the water pump was definitely updated for those engines.

My assumption is that the part # at the bottom is the newest one. I'm not sure though what model/year E9x vehicles used which water pump. I'm trying to figure this out because my assumption is the newest part # is a revised, more robust part that is less likely to fail and I just want to see if it's possible to determine when BMW started putting these in cars from the factory.

All I know is that the bottom part # is what you find at places like getbmwparts.com or ECS Tuning, so I would hope it's the newest and most durable part.

Does anyone know where or how someone can figure out what models/years used which part #? I've tried looking on Google and on Bimmerpost, but I've had no luck. I posted in this thread: http://www.e90post.com/forums/showthread.php?t=807187&page=9 but no one has replied with an answer (I understand it may be difficult to get one). Someone did list some models and years with the part numbers, but I have no idea where they got their information and my assumption is that the models and years they listed are simply cars that can use that part #.

I know this is all just a theory, but I'm just trying to find anything that might give some people more clarity on the situation and hopefully some peace of mind for not only myself, but others. Many of these cars are used as everyday drivers and even for long distance trips. It could be dangerous for the engine to shut off with little or no warning due to a failing water pump.