What is the damage of abnormal water temperatures?

The cooling system is crucial for the continuous and stable operation of the engine. So, at what temperature should the engine's coolant operate for optimal performance?

1. Hazards of High Temperature: When the temperature is too high, the engine oil deteriorates, leading to improper lubrication. This results in a significant decrease in the strength of engine components and excessive thermal expansion, which can cause scratching. Additionally, because the pressure from the turbocharger remains constant, high temperatures lead to an increase in the intake air temperature, which reduces air density entering the combustion chamber, resulting in a decrease in diesel engine power.

2. Hazards of Low Temperature: Low temperatures reduce engine thermal efficiency. The viscosity of lubricating oil increases, leading to greater frictional losses in the engine. Low temperatures also cause rough combustion in the engine, resulting in corrosion and wear of the cylinders and exacerbating the tendency to produce cavitation erosion in the engine water jacket.

When temperatures remain low, close to the thermostat opening temperature, the thermostat may repeatedly open and close (commonly known as thermostat oscillation), increasing the risk of thermostat damage.

Diesel engine exhaust temperatures can reach up to 600 degrees Celsius. Engines are not afraid of heat; on the contrary, an appropriate temperature is beneficial for improving engine thermal efficiency, reducing emissions, and enhancing lubrication to reduce fuel consumption.

The most sensitive to heat is actually the engine's lubrication system. However, with the improvement of lubricating oil performance, optimization of lubrication cooling system design, and the popularity of electronic control engines, the optimal operating temperature of the engine's cooling system has also significantly increased, reaching above ninety degrees Celsius...

If genuine coolant and a pressure cap below 0.5 bar are used, the engine's optimal temperature is between 90°C and 100°C.

If genuine coolant and a pressure cap above 0.7 bar are used, the engine's optimal temperature is between 95°C and 105°C (the pressure cap is determined by the system pressure design and should not be arbitrarily changed). Nowadays, many mainstream engine manufacturers set the thermostat fully open temperature to 95°C to ensure the engine operates at its optimal temperature.

At the same time, the torque limit temperature set by engine manufacturers for electronic control engines is generally higher than 105°C.

When the water temperature exceeds a certain limit, the dashboard will issue a warning, and electronic control engines will actively limit torque and reduce power. After torque reduction, due to the decrease in heat dissipation, the cooling system can quickly return to normal water temperature, protecting the engine from damage due to high temperatures.

The purpose of setting water temperature alarms by the OEMs and high-temperature torque limiting by the engine is solely to remind the driver that there is a risk of further temperature rise and prompt them to quickly investigate whether there are any abnormal factors.

If high-temperature warnings occur in extreme environmental and operating conditions, and the engine coolant is sufficient with normal oil pressure, the engine can continue to operate before reaching the torque limit shutdown point, without causing damage to the engine.

▲Approaching the red line, but without water temperature warning and buzzing sound, you can continue driving.