Just did the water pump replacement yesterday on my 528. I was changing the belts and when I inspected the pulleys the water pump pulley could be rocked back and forth from shot pump bearings. Dang it! That must have been what the squeaking at idle was coming from for the last year. Anyway, Friday afternoon and I need the car for the weekend. I called NAPA and they had three different kinds to choose from. I said I wanted one with a metal impeller, so he brought out two (the third was a rebuilt). I ended up getting the Saleri which was their "OEM" pump for $82. The other one had a metal impeller as well, but it was the cast version, which does not look well made to me. I was surprised how cheap a new Bimmer pump was. Unless you have a M5. Then you get to shell out $500. hahahahah. Sold mine a year ago.
Anyway, the design was about the easiest pump swap ever. But I managed to almost bungle it up, which I will admit here so hopefully others will learn from. After getting it all back together I started the car to start refilling the coolant. The car immeadiatly made a bad rattling noise. Turned the engine off and looked around. I cross threaded the fan to the pump and it was hitting the fan shroud! Dang! I thought it seemed firm going on, but I remember thinking its too big to cross thread- wrong. Its very awkward to hold the fan and get it started in the cramped space. Just be careful and if possible, get it started by just rotating the fan. I had to do the whole job over and take the pump out to repair the threads.
So today Im replacing the precat O2 sensors. Looks like a real joy...