activation for the viscous fan clutch is at a very high temp. although they may go out, they typically are not at fault. you can do a search on viscous fan clutch or VFC to get more info on this. it's difficult to get a sense of how hot the radiator fins are because they are very efficient in dumping heat specially with wintertime ambient temps. the top of your radiator should at least be very hot to the touch. if you think the radiator is not cooling then either it is clogged or the thermostat is not functioning properly. there was a report that there is possibly a bad batch of thermostats out there. re: the water pump - it will start weeping coolant when it is shot so if you have no coolant on the floor it's probably ok.
BTW, "Mercedes" thermostats are either Wahler or Behr. the Wahler thermostat is stamped with the brand. the Behr has a "made in Germany" & "BTT" stamped on it...
1993 300e-2.8 - gone now <sigh>
"Do not adjust your mind, it's reality that's malfunctioning"