A cooling system for a hydrogen hybrid locomotive including a set of electric traction motors and a hydrogen fuel cell system for providing electric power for driving the traction motors. The cooling system includes a radiator for extracting heat from cooling fluid circulated through the hydrogen fuel cell system and a circulation system. The circulation system has a pump for moving the cooling fluid through the circulation system, a first circulation path including a radiator output valve for controlling a selected amount of the cooling fluid provided by the pump to a cooling fluid inlet of the hydrogen fuel cell system through the radiator, and a second circulation path including a bypass valve for bypassing a selected amount of the cooling fluid provided by the pump around the radiator and to the cooling fluid inlet of the hydrogen fuel cell system. A fan system provides air flow across the radiator. A control system selectively sets a position of the radiator output valve and a position of the bypass valve such that the cooling fluid provided by the first and second circulation paths maintains a selected approximate temperature at the cooling inlet of the hydrogen fuel cell system and selectively controls a speed of the fan to control cooling of the hydrogen fuel cell system.