Hi,
it´s nice to carry on this pretty old thread.

As your thermostat is working probably and the coolant temperature is still too low, the cause will be a worn viscous clutch of the cooling fan.The clutch is permanently tight and at cold engine the fan can not idle, even if the engine is working with high revolutions.
Testing: Cold engine: The fan must be turnable easily with just one finger. As you need much more power, a strength hand for example, the clutch is worn an must be replaced.

Beste Grüße
Tim