Kubota generator runs but coolant temperature remains abnormally low, causing wet stacking and unburned fuel in the exhaust.

Safety first: Allow the engine to cool before opening the cooling system. Wet stacking can lead to carbon buildup and fuel dilution of oil.

• Check operating temperature: Compare controller temperature reading with an infrared thermometer at the thermostat housing. If the engine never reaches normal operating temp, suspect thermostat.
• Thermostat replacement: Drain coolant to below thermostat level, remove housing, and replace the thermostat with a Kubota-specified temperature rating. Refill and bleed air.
• Load the generator: Periodically run the generator at 60–80% of rated load for at least an hour to burn off deposits and prevent wet stacking.
• Sensor check: If the engine feels hot but the controller reads low, test and replace the coolant temperature sensor as needed.