What was found
(CAN) DURING CLIMB OUT THE FLT CREW NOTICED THE OIL TEMPERATURE RISING TO THE RED LINE. THE OIL COOLER SWITCH WAS SELECTED FROM (AUTO) TO (MANUAL) OPEN WITH NO RESOMNSE. THE OIL TEMPERATURE CONTINUED TO CLIMB. THE ENGINE WAS SHUT DOWN ANDTHE PROP WAS FEATHERED. THE AIRCRAFT RETURNED TO BASE. DURING TROUBLESHOOTING, MAINTENANCE STAFF FOUND THE OIL COOLER DOOR ACTUATOR WAS INOPERATIVE. THE OIL COOLER DOOR ACTUATOR WAS REPLACED AND THE AIRCRAFT WAS RETURNED TO SERVICE.