In celsius, 100 degrees is the boiling point of water (much less confusing than Fahrenheit, don't you think?). But you don't just put water in the cooling system; you put a mixture of antifreeze and water which has a slightly higher boiling point, perhaps around 105 to 108. In addition, everything is under high pressure which further raises the boiling point of the mixture to around maybe 115. I don't know about on your car, but on my 300E the "red zone" on the temp gauge is at 120 degrees.

Once the water starts to boil or bubble, you have a gas/liquid mixture rather than just liquid flowing through the cooling jackets. The gas will not absorb heat as quickly as the liquid, and the temperature of the metals shoots through the ceiling quickly, resulting in warpage or other damage. Rapid cooling (like turning the engine off or - worse yet - adding cool water to the cooling system) can cause cracks in the metal, much in the way an ice cube cracks when you drop it in a glass of water. In all cases, the key to avoiding damage is to prevent boiling from occurring in the first place.

As long as your coolant/water mixture is not boiling, you are fine. And 85 celsius is not even near the boiling point.

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280