Controller displays F05 – High coolant temperature shutdown during operation

Safety first: Allow the engine to cool completely before opening any part of the cooling system. Hot coolant can cause severe burns.

• Check coolant level: Inspect the expansion tank or radiator fill (if accessible). Top up with the correct MTU-approved coolant mixture if low. Investigate and repair any visible leaks.
• Inspect fan and belt: Verify that the radiator fan turns freely and that the drive belt is intact and properly tensioned. Replace worn or broken belts and check pulleys for damage.
• Clean radiator and charge air cooler: Examine the radiator fins for dirt, dust, or debris. Clean with low-pressure compressed air or water from the clean side out, taking care not to bend fins.
• Check coolant temperature sensor: Inspect the sensor and wiring harness. If the engine is not actually overheating (verified with an infrared thermometer or mechanical gauge), replace the sensor.
• Verify jacket water pump operation: Ensure the engine-driven coolant pump is not leaking and that hoses are not collapsed or kinked.
• Test run: After corrections, clear the F05 alarm and run the generator while monitoring coolant temperature. Persistent overheating requires professional diagnosis of the cooling system and thermostat.