I just got my share of amber and red overheating lights this Saturday as I was about 70 miles into a 180 mile trip. Before I left I topped off the coolant and may have put in litterally "a little" too much.
As a former e46 owner I was surprised to learn of a few things on the e90, the reservoir has some kind of an overflow device which let out quite a bit of my antifreeze. Most important is that I have learned the e90 has an electrical water pump and t-stat. Not knowing I added coolant and tried to bleed the air the traditional way with the bleed screw as I had done a few times on my e46 after changing the expansion tank, waterpump and tstat. Well I couldn't bleed the system on my e90 this way and now I know why.
The worst part is that I think I may have fried my waterpump. When I try to bleed the air with the technique I just hear the water pump make a tiny motor sound but hear no water what so ever. Kind of sounds like a motor running inside but there is no drive attached to the water impeller. The sound goes on for 2 seconds then off for 1 second, on for 1 second off for 2 or 3 seconds. Has anyone had this happen? I thought the water pump was maybe 2 hundred bucks and was going to change it either way but after find that $396 is the cheapest I am debating this.
Any help or experience with a faulty water pump would be great.