I also have a bad ac fan on my 2001 X5 4.4i and I am wondering the AC fan or so called Auxilary fan has something to do with the main engine fan. I've been driven about one month now without AC fan because I don't use the AC. I may not need to replace it right now if I don't turn on AC. I just worry whether my car will be overheated if I drive in the hot summer days even though I don't turn on AC. Does anyone have any idea? So far, I've been driven without any problem at all and my temp guage remains staying in the middle. Please advise.