I'm assuming its part number 13 - I'm almost certain it is.

http://www.realoem.com/bmw/showparts...89&hg=17&fg=05

I was doing some reading over on bimmerforums. Do I have to remove the fan and/or the fan shroud to get to the expansion tank or not? I'm not sure if I do or not. What size spanner do I need for the fan if I have to remove it?