Kubota D1105 Overheats Under Sustained Load
Fault Codes & Symptoms
Overheating Related symptoms: - Reduced heater output in cold weather - Coolant may appear discolored or contain debris when drained The engine temperature gauge goes into the red and the overheat alarm sounds, but only after running under heavy load for 15-20 minutes. It runs fine at idle or light loads.
Confirmed cause: Internal radiator restriction. A borescope inspection through the radiator inlet neck revealed significant scale and sludge buildup in the radiator tubes, restricting coolant flow. Repair performed: The radiator was removed and sent to a radiator shop for professional cleaning. A standard "rod and boil" procedure was performed to remove the internal deposits. The system was then reinstalled with new hoses and fresh coolant meeting manufacturer specifications. Verification: The engine was run under a sustained heavy load for 45 minutes. The engine temperature gauge remained stable in the normal operating range, and the overheat alarm did not activate. Technician notes: - This type of failure is common on equipment with poor cooling system maintenance history. - Using supplemental coolant additives (SCAs) or incorrect coolant types can accelerate scale buildup. - An infrared thermometer can be useful to spot large temperature differences across the radiator core, which can indicate blockages.