The fan should spin freely when its cold... you could grab it with your hands (wrapped in a towel) when idling. When ithe motor is hot the clutch will be working and the fan will spin in relation to the motor speed. You don't want to grab it then.
What kind of motor is in there? ...meaning which V8 designation? For sure there is a diagram for you somewhere on the web, or here. I have an early 90's S-class shop printed shop manual...but that won't help you.
