auxilary fan for a 300e

[az300e]

I have a 1987 300E. When I am driving the engine temperature is normal. But if I sit in traffic or let it idle the engine temp starts to climb. The auxilary fan does not turn on until the temp is almost in the red. Is this normal or should the auxilary fan kick on before it gets that hot? The radiator has been replaced in the last year. Could this be a bad thermastat or is there something else. Any imput would be appreceated.

 

[HamishsCar]

Running Temps

The Bi-metalic strip in the Viscous Fan clutch controls it's speed causes the fan to engage at 96'C and off at 102'C and remain fully engaged at anything over 3250rpm.
I recently had to replace Rad in my 300TE 226,000 MILES ON THE ORIGIONAL so hope new one lasts as long,after which it ran very cool 45-65'C I checked then changed the thermostate as it was'nt closeing now steady at 87'C all day.
So Suggest you check the thermostate first to see if its jammed
Cheers Hamish