I JUST GOT THIS 99E320 A COUPLE OF MONTHS AGO AND HAVE NOTICED THAT THE COOLANT GAUGE READS JUST BELOW 80C AND THIS WEEKEND THE GAUGE STARTED TO READ A LITTLE ABOVE 80C AND WHILE IN STOP AND GO THE TEMP WENT CLOSE TO 100C. THE WEATHER WAS WARMER THAN IT HAS BEEN. IS THIS NORMAL FOR THIS CAR.
THANKS

Not normal. Sounds like you're due for some cooling system service including a new thermostat. Check the archives on thoughts of MB brand coolant vs other brands of coolant.

To qualify, getting to 100 occassionally is not a problem. Coupled with staying below 80 when you've been driving a while suggests that the thermostat is not closing fully. Not a stretch to suggest that it's also not opening fully.

Sixto
91 300SE
87 300SDL
83 300SD

On the 4valve@cylinder & 3valve@cylinder the normal engine temp is between 90 & 100C. IN fact for emissions MB runs the engines at these higher temps! IN fact ALL(newer) engines run hotter today than 20 years ago!

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REPLACE THEMOSTAT AND MB COOLANT.
TEMP RUNS ABOUT 83C TO 95C AND VARYS DEPENDING ON TRAFFIC. DOES ENGINE TEMP VARYS MORE ON NEW MBZ WITH ELECTRIC FAN THAN OLDER ONES WITH ENGINE FAN.
THANKS