Sounds like it is probably functioning normally now. It should run around 90 on the highway and 90-100 or higher in traffic. After the thermostat starts to get old, it starts to open at a lower temperature. That is why a new thermostat makes the car run warmer.

An 87C Mercedes thermostat starts to open at 87C +/- 2C. It is only fully open at and above 102C. That means it will restrict coolant flow through the radiator at any temp below 102C.

Looks to me like they did fix it properly.

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Ali Al-Chalabi

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