DIESEL ENGINE

A diesel engine is provided with an EGR line G configured to recirculate a portion of exhaust gas, discharged from an engine body , to the engine body as combustion gas, an EGR cooler provided in the EGR line G and configured to cool exhaust gas by coolant, a coolant supply device configured to supply coolant to the EGR cooler , and a control device configured to activate the coolant supply device when the engine body is in operation and a temperature of the engine body is lower or equal to a preset prescribed temperature.