As far as I can remember the 400i doesn't have any bleeding points, the procedure is to remove the radiator cap and fill the system, open the internal heating taps and then run the engine at idle (the cap is still off), let the engine warm up until the thermostat opens, keep topping up the radiator until it reaches the correct level, which is about 15mm below the connection between filler neck and radiator. Refit the cap and run the engine, any excess coolant will be transfered to the expansion tank.
