The electrically-heated thermostat is an installed on the thermostat housing and its operation is controlled by the ECM. If a faulty thermostat is suspected check the ECM for fault codes using a BMW scan tool. The housing assembly also had to be removed to carry out this, you will need to drain the
Radiator and engine block water. Next, bolt off the cooling fan and cowl and then clip of the electrical harness connector from the thermostat housing. Use a sheet to cover the alternator to avoid rusting by the coolant, remove the rivet type retaining clips and pull out the hose nipples from the housing. Pull the thermostat housing from the front of the engine with the nut on the top of the engine lifting eye unscrewed to better be removed. It is the process of the opposite of that on removal, the sealing faces must be clean of oil, a new sealing gasket is to be used. Last but not least you just add the coolant to the system and then release the pressure or more simply, bleed it.