You can use an allen/hex socket insert (6mm or 8mm don't remember exactly, see the manual) to get it out. You can buy these inserts at Autozone, Pep Boys, Walmart, or Home Depot. The set (3mm - 10mm) usually costs about $10 but you can buy individual ones for $2.99ea. Also you will have to hold the fan from rotating by inserting a L shaped allen/pin in the specified hole. Life is much easier if you get the radiator out but keep in mind you will have to remove the bumper for this. Pls remove the shroud, loosen the tensioner and you may have to remove the fan clutch bearing. I replaced the fan clutch, bearing, tensioner, serpentine belt and cleaned out the radiator on my 190E 2.6 in Oct 2001. It took me about 4 hrs for all this. It will be a little painful to work on this car since there is not much room to work with. Pls let me know if you need detailed instructions, I'll be happy to post'em. Good Luck.
86 BMW 325e