Coolant circuit for an internal combustion engine

The circuit has a radiator (2), at least one mechanically driven coolant pump (3) and at least one electrically driven pump (4) for a cooling circuit with a coolant feed (8) and heat exchanger (7) and a heating circuit with a coolant return (9') and heat exchanger (7'). The mechanical pump and/or electrically driven pump are associated with the heating and/or cooling circuits (5,5'); the mechanical pump can be turned on and off or choked.