100 degrees C shouldn't be too hot. That's the third has mark, between 80 and 120. My temp gauge will climb slightly higher than the 100 C (110 estimate) mark. It only gets that warm when climbing 3,000ish feet, with three 200lb passengers, luggage, at Hwy speed, in 100 degree desert heat.

My radiator might not be new, but it does fine. The red line is at 120 C and boilover for the coolant is a little higher. Just keep it out of the red I say.

Now that fan that sits in front of the radiator, I have no idea if that works as it should....

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1982 240 D, 308,000 - 321,127 miles (sold)
1982 300 TD,166,500 - 226,000 miles
1998 E 320, 120,000 - 144,000 miles
2005 C 230 K, 26,000 - 77,000 miles (sold)