The Function of Thermostat in Diesel Engines and Consequences of Removal

Currently, most diesel engines use wax - type thermostats with stable working performance. When the temperature of the cooling water is lower than 83°C, the thermostat valve closes. The cooling water can only circulate in a small loop within the diesel engine without passing through the water tank for a large - scale circulation. This accelerates the rise of the cooling water temperature, shortens the warm - up time, and reduces the running time of the diesel engine at low temperatures.

When the coolant temperature reaches the opening temperature of the thermostat valve, 83°C, as the temperature of the diesel engine gradually rises, the thermostat valve gradually opens. More and more coolant participates in the large - scale circulation for cooling, and the heat - dissipation capacity increases accordingly.

Once the temperature reaches or exceeds the full - opening temperature of the main valve, 95°C, the main valve fully opens, and the auxiliary valve completely closes the small - circulation passage. At this time, the heat - dissipation capacity is maximized, ensuring that the diesel engine operates within the optimal temperature range.

When it is found that the water temperature of the diesel engine is too high, instead of carefully checking whether there are reasons in the diesel engine cooling system, such as a damaged thermostat or excessive scale in the water tank, some people simply think that the thermostat hinders the circulation of the cooling water based on their perception.

What will happen if the thermostat is removed due to high water temperature?

1. Excessive fuel consumption

After removing the thermostat, the large - scale circulation dominates. The engine dissipates more heat, resulting in more wasted fuel. When the engine runs below the normal working temperature for a long time, the fuel combustion is incomplete, which further exacerbates fuel consumption.

2. Increased oil consumption

When the engine runs below the normal working temperature for a long time, the engine combustion is incomplete. More carbon black enters the engine oil, making the oil more viscous and increasing the amount of sludge.

Meanwhile, the water vapor generated by combustion easily condenses with acidic gases. The resulting weak acid neutralizes the engine oil, increasing oil consumption. In addition, the diesel entering the cylinder is poorly atomized. The non - atomized diesel washes away the oil on the cylinder wall, diluting the oil and increasing the wear of the cylinder liner and piston rings.

3. Shortened engine life

Due to the low temperature, the engine oil has high viscosity and cannot lubricate the friction parts of the diesel engine in time. This increases the wear of the diesel engine components and reduces the engine power. The water vapor generated by combustion easily condenses with acidic gases, aggravating the corrosion of the engine body and shortening the engine life.

4. Removing the thermostat brings nothing but harm!

When it is found that the water temperature of the diesel engine is too high, if it is confirmed that the coolant level is normal and the water in the water tank is flowing, indicating that the water pump is working properly, it is necessary to check whether the thermostat has failed.

The method is as follows: Remove the thermostat from the machine and put it in hot water at 82 - 85°C. If the thermostat cannot open more than 1mm, it indicates that the thermostat has failed. If it is put in water at 95 - 100°C and taken out after a few minutes, and the main valve of the thermostat is fully open, it indicates that the thermostat is working normally; otherwise, it indicates that the thermostat has failed.

Once it is determined that the thermostat has failed, a new one should be replaced in time. Otherwise, the diesel engine will run at a low (or high) temperature for a long time, causing abnormal wear or overheating of the diesel engine and leading to serious accidents. The new thermostat should be tested for quality before being installed. Never operate the diesel engine without a thermostat, as this will cause the diesel engine to run at a low temperature for a long time.

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