The causes and diagnosis of high engine water temperature

Excessive engine water temperature means that the water temperature gauge indicates that it is in a high temperature area or a position above 100°C; the radiator cover appears boiling and water spray; the engine makes a crisp knocking sound during driving; the engine is easy to stall.

The harm of high water temperature in engine cooling system

1. If the water temperature of the engine cooling system is too high, it will cause the fuel injected into the cylinder to burn prematurely, causing the engine power to drop.

2. All moving parts expand excessively due to the effect of high temperature, which causes the original matching clearance to change, which greatly reduces the working capacity of the bearing and destroys the normal working condition.

3. Excessive temperature will cause the viscosity of the oil to decrease, cause the oil film of each lubrication part of the engine to be destroyed, accelerate the wear of the parts, and in severe cases may cause accidents such as tile burning and cylinder pulling.

4. Too high temperature will accelerate the aging and damage of rubber parts, causing local deformation, cracking and burning of rubber parts, causing water and oil leakage of the engine.

There are many reasons for the high water temperature of the engine cooling system, which can generally be classified into two categories: mechanical failure of the cooling system and electrical control failure of the cooling system:

1. Mechanical failure of cooling system

① Too much scale on the radiator and engine water jacket causes poor heat dissipation. 

② The thermostat is damaged, so that the coolant cannot enter the radiator smoothly to form a large circulation. 

③ The water pump is damaged or the transmission belt is slipping, causing the water pump to work poorly. The water pump can't work normally, so it can't generate enough water pressure, which reduces the circulating flow of cooling water. 

④ Lack of antifreeze, resulting in insufficient cooling. 

⑤ There is air in the cooling system, causing the cooling water to not circulate normally. 

⑥ The cylinder head gasket is damaged, causing high-temperature and high-pressure gas in the cylinder to enter the cooling system, causing the water temperature to rise quickly. 

⑦ The coolant leaks, causing the engine temperature to rise. Water leaks mostly in radiators, water pumps, cylinder blocks, cylinder heads, cylinder gaskets, heater radiators, water pipes, rubber hoses and water drain switches.

2. Electric control failure of cooling system

① The cooling electronic fan does not work, or there is no high or low speed gear, so that the forced air cooling of the electronic fan does not work, causing the water temperature to be too high.

② The dual temperature switch is faulty. There are two switches inside the dual temperature switch: one switch is turned on when the water temperature reaches about 90℃, so that the fan runs at low speed. When the water temperature is lower than 84℃, the switch turns off again and the fan stops working; the other switch is when the water temperature reaches about 100℃, turn on the fan to run at high speed to enhance the cooling capacity of the fan. When the water temperature drops to 90℃, the fan returns to low speed. If there is a problem with the switch, it must be replaced with a new one during maintenance.

③ The electronic fan relay is damaged, the electronic fan does not operate, and the water temperature is too high due to no forced air cooling.

④ The air conditioning system is malfunctioning. When the air conditioner is turned on, the electronic fan must be operated at a low speed. When the air conditioning system pressure exceeds a certain value, the electronic fan must be operated at a high speed. If it is abnormal, it will increase the load of the engine, consume the heat dissipation performance of the cooling system, and cause the water temperature to be too high. In addition, if the air conditioning refrigerant is filled too little or too much, the cooling effect will be reduced.

⑤ If the water temperature sensor is damaged or the wrong signal is sent, it will cause the engine cooling water temperature to be abnormal.

⑥ The water temperature meter displays abnormally. Special measuring tools can be used to detect the measurement base point and range of the water temperature meter. If it is not normal, the water temperature meter needs to be replaced.

⑦ Improper adjustment of the fuel supply system caused the flammable mixture to be too lean. If the mixture is too lean, the combustion rate will be slow, and most of the heat generated after combustion will be lost to the cylinder wall, which will cause the engine cooling water temperature to rise.

⑧ Improper adjustment of the ignition system. If the ignition advance angle is adjusted too late, the mixture cannot be burned in time and fully burned. The unburned fuel is supplemented in the exhaust throat, which not only affects the engine's power output, but also increases the temperature of the engine's cooling system.