190D22,

If you have an electrically operated clutch for the main fan, the fan will spin freely when the clutch is disengaged, and then it will spin in direct proportion to engine speed.

If you notice the electric fan turning on at about 105 degrees Celsius then you should try popping the hood and looking to see if the main fan is roaring. It engages and disengages on my 1986 190E 2.3-16 with an audible click. And the fan makes a significant roar from beating the air as it draws it across the radiator.

On my 190E 2.3-16 it is "normal" and the car has always exhibited this tendency, to heat up at idle. It used to scare me as my older Diesels never flinched on the temperature gage - 175 degrees Fahrenheit on the old 220D, and 80 degrees Celsius on the 240D's, regardless of load, ambient temperature, city, stop and go, highway driving, etc.

I can look up the specs on the temperature sensors on my car, but you should confirm what kind of clutch you have and how it is activated. Maybe someone reading these posts knows for sure what the clutch mechanism is for your car. A viscous clutch will have some drag so it rotates at something like 1200 rpm max (varies with engine speed somewhat) until the clutch engages. Then the fan speed varies with engine speed to about 3200 rpm max, when the clutch basically can no longer handle the torque load of the fan and the fan speed tops out regardless of how much higher the engine turns.

Well, good luck and I hope some of this helps. Jim

edited for clarity

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)