DrTofu

Hey, I'm replacing the water pump on my 300E and I cant get the center hex screw out of the fan clutch. I got the 3 outter ones off(5mm) but i cant find a hex socket that fits, I've tried 4-7 cause thats all ive got but they dont work. The diagram/steps that i was given says it's 7mm but it doesnt fit, and i can't see to measure it. Anyone know off hand what size it is, before I go out and buy a whole set of hex scokets.

Thanks
Matt