Fault Diagnosis for the Engine Cooling System

2019.06.25

To troubleshoot engine overheating fault, keep it in mind that an overly full oil sump will raise the oil temperature and transfer it to the oil cooler cooling system.

1) Temperature sensors must function properly, as any high temperature and overheating will cause serious damage to the piston and cylinder sleeve.

2)The engine thermostat must operate correctly to make sure that the engine operates within the optimum temperature range. Overheating or undercooling can shorten the engine life. The thermostat controls the coolant temperature. When the coolant temperature is lower than the operating temperature, the thermostat is closed. Then, the coolant flows into the water pump inlet through the bypass. When the cooling temperature rises to a certain degree, the two thermostats are opened at the same time, and the coolant flowing to the bypass pipe starts to be restricted. At the engine operating temperature, the thermostat opens and the bypass valve closes.

Note: Without a thermostat, the engine shall not be operated. At this time, the coolant channel has low resistance, and the coolant directly flows into the pump inlet through the bypass without restriction, which will cause the engine to be overheated.

For more specific information, refer to the maintenance manual for the vehicle or consult with the Yutong service engineer.