Mercedes also changed to a torx head T55 for the 606 engine in my '98 e300. I bought one from a Mercedes dealer when I changed my fan clutch a year or two ago. Either by design or accident, that bolt also accepts an 8mm hex socket. I used the 8mm stubby socket made by Stahlwille (a Mercedes tool part no. 103 01 98) which I bought from Samstag to put it in my car. (The Mercedes parts salesman told me I could use an 8mm socket when I bought the torx head bolt.) You have to use a stubby socket, because there is so little clearance between the radiator and the bolt.