I just went through this on my 300CE , I made the tool to hold the fan and borrowed the proper socket for it. That didn't work so I tried a Torx bit, 50 was too small and 55 was too big. I found a short bolt extractor (5/16") made by Hanson that almost grabbed but not quite . I evacuated the A/C and removed the condenser , along with the rad and aux. fan . I then had room to drill the inside of the bolt about 1/4" deeper with a 5/16" bit and used the bolt extractor to remove the bolt.Simple , no?
. I was doing the head gasket at the same time so I had to drain the coolant anyways. The A/C evacuate/recharge was $150 and all the time and scraped knuckles make this a very expensive bolt . If the only reason to remove the bolt is to change the fan tensioner (on a 103), it can be removed without removing the bracket bolt on the front cover completely , just loosen it enough to get the bracket out of the way, then goop some RTV on the bolt before you tighten it to avoid a oil leak there. Good luck