I would check the accuracy of the temp gauge on the car. If it is accurate, it may be possible that you got a defective thermostat. You can always boil the thermostat in a pot of water with a thermometer to check the accuracy of it.

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Ali Al-Chalabi

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