Fault Phenomenon: Hongda HBT80 coolant temperature is normal when cold. After continuous operation for 3 hours (operating temperature), the radiator boils, coolant overflows, and eventually overheats.

Troubleshooting Process:
– Checked radiator fan: fan runs normally, sufficient airflow.
– Checked thermostat: opens normally.
– Checked water pump: pump impeller not corroded.
– Measured radiator inlet-outlet temperature difference at operating temperature: found temperature difference too small.

Root Cause: Internal cooling passages of the radiator are blocked, leading to decreased heat exchange efficiency.

Required Parts: Radiator assembly and cleaning agent.