I think we may be getting models confused. I also had a 300TE (M103) and used the cutoff allen wrench trick (8mm - not 5mm - I just measured it). It is near impossible to use on the C280. That is why I bought the MB tool for the C280. I can force it into the bolt and break it loose, but cannot thread it out far enough to rotate the bolt with my fingers. That is how I came to the 8mm ratchet box wrench idea. My pulley tool is .225" - I think 3/16 (.1875") would be too loose, and it can cock and distort the hole. I used to use the peg hook tool also. It won't work on this engine - way too short. It is a pain to get the tool engaged in the pulley on the M104 anyway, with the additional gingerbread at the front of the head. I never had much luck pulling the pump without loosening the A/C Compressor and P/S Pump. I know the techs do it, but I wasted more time trying and just bit the bullet - it wasn't that bad. I worked on the front of the engine in the 300TE several times in 250,000 miles and it was easy. I've been into the C280 twice (belt and later an idler pulley) and it is an entirely different, far more time consuming operation.