The coolant temperature is abnormal, which can be solved from the following aspects:
a. The oil level in the oil pan is too high
Analysis: If the oil level in the oil pan is too high so that the connecting rod journal is immersed in the oil, when the diesel engine is running, the crankshaft and the big end of the connecting rod stir the oil and generate additional heat due to friction. For the above reasons, additional heat is transferred to the coolant in the oil cooler, causing the coolant temperature to increase additionally.
b. Incorrect pressure cap or failed pressure cap will cause excessive loss of coolant and overheating of the diesel engine;
c. Air or combustion gas enters the cooling system
Analysis: The air entering the cooling system will cause the coolant to overflow due to heat. At the same time, the air will expand and the pressure of the cooling system will be high, causing the pressure cap to open, resulting in increased coolant loss;
A leaking cylinder head gasket that allows gas or compressed air to enter the cooling system will have the same consequences;
If the air or gas entering the cooling system is not discharged in time, it will return to the water pump inlet with the coolant, causing the water pump flow to decrease and causing the diesel engine outlet water temperature to increase;
How to check whether combustion gas enters the cooling system:
When the diesel engine cools down to below 50 degrees, remove the radiator pressure cap. Install the pressure cap with the pressure relief valve removed on the radiator to allow gas to flow out along the overflow pipe. Attach one end of a rubber hose to the radiator overflow pipe and insert the other end under the water surface in the water container. (The pressure cover must be sealed during the test), start the diesel engine and run at rated speed until the outlet water temperature reaches 80 degrees. Check for bubbles in the water container, indicating combustion gases are leaking into the cooling system (Note: The coolant temperature must be stable during the test, if the temperature rises it will cause artifacts due to the expansion of the coolant in the system).
d. The cooling water pump flow rate decreases;
Analysis: Loose belts or damaged water pump impellers will also reduce the flow rate. However, before checking the flow rate and replacing the water pump, you should check other relevant parts according to the troubleshooting procedures.
e. The radiator fins are blocked and the air volume passing through the radiator is reduced;
f. Improper operation of the thermostat will cause the diesel engine to overheat (note: the diesel engine must not run without a thermostat. When the thermostat is not installed, the resistance of the bypass channel is small, and the coolant flows directly to the water pump outlet through this channel, which will Causes the diesel engine to overheat.)
g. Electrical circuit failure, water temperature sensor failure or thermometer failure.
