If the new thermostat never lets the car go above 82C and the coolant temp gauge is working properly then the new thermostat is faulty.

REMEMBER, an 87C rating means the thermostat STARTS to open at 87C. The thermostat does not fully open until 102C! In theory with a new thermostat working exactly as it is supposed to, the engine should never be below 87C. When my car starts running a constant 80C on the highway, this is when I replace the thermostat. That brings it up to 90C where it should be.

The old one you replaced was working properly. If you want your car to run at a temperature other than what the engineers decided it should run at, then don't get an 87C thermostat.

I would find that old one that kept the car a nice 90C, put it back in and make sure all the air is bled out.

__________________
Ali Al-Chalabi

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