Why does my BMW overheat?

[Doughnut]

okay, but you should be testing the fan clutch at idle speed right? Because fan should have the most "grip" at idle right? The faster the engine turns, the easier it should be to stop it right? Or does the fan clutch hold the fan with the same amount of resistance all the time? (I sound like I don't know anything, but I really don't know jack about fan clutches, except how to make the tool that holds them).

Scott.
The fan in your BMW has a viscus (oil filled) coupling in the middle, and is harder to turn when hot to cool the motor, and easier to turn when cold to get it to operating temp asap.
lol, thought i'd make you look like the ultimate noobie Scotty!

So therefore, to test -
Without your engine running, pop the bonet and attempt to "free spin" the fan blades, if it spins very easily straight away (like mine) its rooted.
Also check around the fan for oil diposits (like mine has) which indicates a leaking seal - rooted clutch.
Thats IMO and how i check em' at work too.

My car still does not overheat BTW