Removing water pump

remove the radiator to have better access.
remove all the belts
now here is the hard part you need to make your own tool or buy the bmw tool to hold the fan belt pulley by the 10mm bolts some how there are many tools that you can use for this just be creative sometime weding a bolt or a big screwdriver does the job too in between the pulleys than loosen the 32mm nut which you can get that wrench at a bicycle shop for a few buck unless you have a bench grinder and can grind a 32mm down to half its thickness or buy the bmw fan pulley wrench and holder there expensive than just remove the water pump. Sometimes they will not come out very easy just to let you know the times I've changed them in my car or others I have had to beat on them with a Hammer to break them off they seize up in there pretty darn good and once you break them you have to continue till its out I recomend any water pump that has a metal impellar or you might end up being stuck doing this job again in the next 6 months make sure the part is German trust me its worth it. Good luck