Liquid cooled, thermostatically controlled internal combustion engine for a vehicle, especially for motor cars

The engine has an operating heat exchanger (5) connected to the engine cooling circuit (3) and exposed to exhaust gas in a controled manner and a heat exchanger (6) for a heating/air conditioning system. A return line (11) from the operating heat exchanger for connection to the heating heat exchanger is treated as of higher order in a control program than the return line (12) connected to the suction side of a circulation pump (13) for the engine.