That is a little too warm. Is it running a solid 100C on the highway with low outside air temps? If thermostat is good and temp gauge is working properly, there might be the possibility of a flow problem. To test the fan clutch, with the engine running that warm you should be able to feel a large volume of air being blown by the fan when you open the hood, especially when it is reved. Just be careful to keep your hands clear. If there is no mass airflow from the fan at those temps, the fan clutch may be suspect as well.

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record