There is nothing in haasman's original post that indicates a problem with the thermostat. His cooling system temperature behavior is normal. There is no need for him or anyone else to "re-engineer" the cooling system.

A lot of guys seem to think that the themostat should maintain constant coolant temperature like the themostat in your house maintains near constant air temperature. This is not true for any car. The thermostat establishes the minimum operating temperature, and it is not fully open until about 10-15 degrees C above the initial opening temperature when the valve just begins to lift off the seat.

The upper end of the normal coolant temperature range is determined by radiator heat transfer capacity and air flow. The electric fan(s) doesn't engage at high speed until about 105C (and this should rapidly drop the temperature to about 100), so the normal operating range is about 80-105C (176-221F), and a temperature range of 100-105C in heavy stop and go traffic, especially in hot weather, is normal. Only if the temperature regularly starts pushing above 105 should one be concerned that there may be a problem.

Duke