The current invention relates to an apparatus for cooling and / or heating a motor vehicle, with at least one
coolant pump (30, 32) for circulating a
coolant in a cooling and
heating system, with a main cooler segment (10), which has a main cooler inlet (11) and a main cooler outlet (12), wherein the main cooler inlet (11) is at least intermittently connected to at least one
coolant outlet (24, 224, 225, 229) of an engine to be cooled (20), in particular an
internal combustion engine, of the vehicle, and its main cooler outlet (12) is connected to at least one coolant inlet (23) of the engine (22), and with at least one other, secondary cooler segment (15, 215, 315, 415, 515) provided in addition to the main cooler segment (10) and at least one other unit to be cooled (60, 61, 70, 80, 90, 97, 170, 186), which is connected to the cooling and
heating system. The invention proposes that the apparatus have at least one bypass line (125, 325) with a
bypass valve (72, 251), which is associated with the at least one secondary cooler segment (15, 215, 315, 415, 515) and is disposed parallel to this secondary cooler segment (15, 215, 315, 415, 515) in the cooling and
heating system of the motor vehicle.