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1. Abnormal coolant temperature can be addressed from the following aspects:
a. The oil level of the oil pan is too high
Analysis: If the oil level in the oil pan is too high, causing the connecting rod journal to be submerged in the engine oil, during the operation of the diesel engine, the crankshaft and connecting rod large end stirring the engine oil will generate additional heat due to friction. Based on the above reasons, additional heat is transferred to the coolant in the oil cooler, causing an additional increase in coolant temperature.
b. Incorrect or ineffective pressure caps can cause excessive loss of coolant and overheating of diesel engines;
c. Air or combustion gases entering the cooling system
Analysis: Air entering the cooling system can cause coolant to overflow due to heating, while the air expands and the cooling system pressure is high, causing the pressure cap to open, resulting in increased coolant loss;
Leakage of cylinder head gasket causing gas or compressed air to enter the cooling system can also have the same consequences as mentioned above;
If the air or gas entering the cooling system cannot be discharged in time, it will return to the inlet of the water pump with the coolant, causing a decrease in the flow rate of the water pump and an increase in the outlet temperature of the diesel engine;
Method to check if combustion gas has entered the cooling system:
When the diesel engine cools down to below 50 degrees, remove the radiator pressure cap. Install a pressure cap on the radiator that has removed the pressure relief valve, allowing gas to flow out along the overflow pipe. Connect one end of a rubber hose to the overflow pipe of the radiator, and insert the other end under the water surface of the water container. (During the test, it is necessary to ensure that the pressure cap is sealed.) Start the diesel engine and run it at rated speed until the outlet water temperature reaches 80 degrees. Check for bubbles in the water container, indicating that combustion gas is leaking into the cooling system (note: the coolant temperature must be stable during the test, and if the temperature rises, it may cause false images due to the expansion of the coolant in the system).
d. The flow rate of the cooling water pump decreases;
Analysis: Loose belts or damaged water pump impellers can also reduce its flow rate, but before checking its flow rate and replacing the water pump, other relevant parts should be checked according to the troubleshooting procedure.
e. The radiator fins are obstructed and the airflow through the radiator is reduced;
f. Abnormal operation of the thermostat can cause the diesel engine to overheat (note: without a thermostat, the diesel engine cannot operate. Without a thermostat, the resistance of the bypass channel is small, and the coolant flows directly through this channel to the outlet of the water pump, which can cause the diesel engine to overheat.)
g. Electrical circuit failure, water temperature sensor failure, or temperature gauge failure.
