Why Does the Coolant Temperature Become Too High?

[Richardson]

Causes of excessively high coolant temperature: 1. Insufficient coolant; 2. Slipping, broken fan drive belt or incorrect fan blade angle; 3. Failure of the fan clutch; 4. Insufficient opening or failure to open of the thermostat valve; 5. Overly rich or lean air-fuel mixture; 6. Engine operating under prolonged heavy load or overload. Methods to handle excessively high coolant temperature are as follows: 1. Immediately reduce speed and, after slowing down, drive the car to a safe area by the roadside to park; 2. Do not turn off the engine immediately. After parking, do not shut down the engine right away because excessively high water temperature can lead to overheating of the piston, cylinder walls, cylinder, crankshaft, etc., thinning of the engine oil, and loss of lubrication. Shutting down the engine could cause some soft metals to peel off, and in some cases, even lead to cylinder sticking; 3. Let the engine idle in place for a few minutes, adjust the air conditioning to the heating mode, set the fan to maximum speed, and open the hood to help the engine dissipate heat. Turn off the engine only after the water temperature has dropped.

[Henry]

I've encountered the issue of high coolant temperature several times, with radiator blockage being the most common cause. Dust and debris accumulate between the cooling fins, obstructing airflow and preventing effective heat dissipation. Water pump failure is another frequent issue, where worn impellers or leaking shaft seals result in poor water flow and inadequate coolant circulation. If the thermostat gets stuck in the closed position, the main cooling circuit won't open, causing the water temperature to spike. Check for aging cracks in hoses or loose connections that may cause leaks, as low coolant levels can lead to boiling. Also, ensure the fan is working properly—motor or belt problems may lead to insufficient cooling. Regular maintenance is crucial, such as cleaning the radiator annually and using high-quality coolant to prevent these issues. Otherwise, engine overheating may cause cylinder head gasket damage, which is time-consuming and costly to repair.

[AugustRose]

When driving myself, I pay attention to the maintenance of the cooling system. Overheating is often caused by insufficient coolant, and the drop in coolant level may be due to minor leaks or evaporation, especially when driving in hot weather. Thermostat failures are also not uncommon; if it doesn't open in time, the temperature can go out of control. When the radiator cap's seal deteriorates and pressure drops, the boiling point of the coolant decreases, making it more prone to boiling over. Checking the coolant concentration ratio is crucial, as improper dilution affects its antifreeze and anti-corrosion properties. Regularly replacing the coolant and inspecting aging hoses can prevent unexpected issues. Additionally, high-speed driving or towing heavy loads increases the cooling burden, so preventive measures like stopping to rest and cool down are essential to ensure safety first.

[DeJuliet]

From an electrical perspective, overheating may be related to the fan system. A faulty temperature control switch can prevent the fan from starting, resulting in poor cooling performance. Check if the relay or fuse is burnt out, affecting power supply. In congested urban areas, frequent fan operation increases the risk of circuit failures. Adding auxiliary fans or upgrading the controller during modifications can improve cooling efficiency, but must match OEM specifications to avoid issues. Faulty sensors may also provide misleading readings, requiring professional diagnosis. Keeping fans clean to prevent dust blockage is also crucial.