What Causes the Radiator to Boil Over?
2 Answers
The reasons for a radiator boiling over are: 1. Insufficient water level; 2. Radiator blockage, causing poor circulation and backflow; 3. Radiator leakage obstructing water circulation; 4. Abnormal operation of the thermostat in switching between large and small circulation modes; 5. Damaged cooling fan or short circuit in wiring causing the fan to stop working, or the cooling fan rotating very slowly; 6. Malfunction of the fan water temperature sensor. The function of the radiator is: When the engine's water temperature is high, the water pump repeatedly circulates the water to lower the engine's temperature, thereby protecting the engine. In winter, when the water temperature is low, the water circulation stops to prevent the engine temperature from dropping.
Boiling over in the radiator commonly occurs when the engine overheats. I've driven many long-distance trips and experienced this several times. The main causes are usually insufficient or degraded coolant, leading to boiling and splashing. It could also be due to accumulated dust or blockages in the radiator, preventing heat dissipation when the fan isn't functioning properly. A stuck thermostat or a faulty water pump, causing poor fluid circulation, can also trigger issues. This happens especially often in summer when engine load increases and temperatures spike rapidly. Preventive measures include regularly checking fluid levels, using a dedicated antifreeze-water mixture instead of plain water (which has poor cooling performance), and cleaning the radiator fins to ensure good ventilation. If it happens on the road, immediately stop the engine, open the hood to cool for half an hour before handling—safety first.
