benmack1, a 1995 E320 has the newer style drive belt tensioner without the brass tensioner rod on the earlier 124 cars. Simply put a socket on the center nut/bolt head and release the tension on the drive belt and slide it off a nearby pulley.

Use a 5mm allen wrench to remove the bolts securing the fan. A 5mm allen wrench (with the short end inserted in the pulley hole) will work in place of the special tool. A 8mm allen wrench with a short cheater bar will work to remove the viscous fan clutch ... but you probably can leave it in place when replacing the water pump. Although I've never replaced a water pump on a 1995 E320 you will likely need to loosen the power steering pump to access the water pump bolt heads and have enough room to remove the water pump. As sptt mentions you will learn a lot the first time you replace the water pump, and by the next time you'll likely have forgotten some of the shortcuts.

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Fred Hoelzle