From back before there were microprocessors a car radiator valve was mainly two layers of different metals fused together in a housing with valve flaps. They had no power connections yet were strong enough to hold against pump pressure, more than strong enough to flip a switch and off the shelf solidly automotive-standard reliable.
I've never seen a thermostatic valve like that.
Almost all thermostatic valves are operated by a cannister full of wax which expands with heat and drives a pin out - the pin is mechanically connected to a flap to seal/divert the coolant. A heavy spring keeps the wax under pressure and pushes the pin back as the wax cools and contracts. On some modern cars the cannister includes an electrical heating element so that the operating point can be varied by an electronic controller.
The bimetallic device you describe sounds like what is often called an 'otter switch' and is simply used to make/break an electrical circuit to operate the fans - it does not generate any significant mechanical force and doesn't directly operate anything mechanical. These have largely been phased out in favour of simple relays driven directly from an ECU.
What is being proposed here could be implemented trivially easily using a couple of otter switches, but I gather the OP wants to use a microcontroller.