Just wanted to add, I observed the same thing as decribed by screedchan today during my trip from Vancouver to Bellingham...while waiting at the Canadian/American Peace Arch border crossing to come back into Canada for around 40minutes, I noticed how the coolant temperature would shoot right up to 110C, then the fan comes on to take it down to 100C...happened 3 or 4 times during the 40 minute wait...A/C was off...temperature reading on dash said 20.5C...after I got up to speed on the highway with the A/C on again, the coolant temperature quickly dropped down to a little above 80C...wow...this is one HOT operating car...

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1995 black pearl/black Mercedes-Benz E420 :