State judgment
When the engine starts cold running, if there is still cooling water flowing out of the water inlet pipe of the water supply chamber of the water tank, it indicates that the main valve of the thermostat cannot be closed; When the engine cooling water temperature exceeds 70 ℃, and there is no cooling water flowing out of the water inlet pipe of the upper water chamber of the water tank, it indicates that the main valve of the thermostat cannot be opened normally, so it needs to be repaired. The thermostat can be checked on the vehicle as follows:
Inspection after engine start: open the radiator water filler cap. If the cooling level in the radiator is static, it indicates that the thermostat works normally. Otherwise, it indicates that the thermostat works abnormally. This is because when the water temperature is lower than 70 ℃, the expansion cylinder of the thermostat is in the contraction state and the main valve is closed; When the water temperature is higher than 80 ℃, the expansion cylinder expands, the main valve gradually opens, and the circulating water in the radiator begins to flow. When the water temperature gauge indicates below 70 ℃, if there is water flowing at the radiator inlet pipe and the water temperature is warm, it indicates that the main valve of the thermostat is not closed tightly, resulting in premature large circulation of cooling water.
Inspection after the water temperature rises: at the initial stage of engine operation, the water temperature rises rapidly; When the water temperature gauge indicates 80 and the heating rate slows down, it indicates that the thermostat works normally. On the contrary, if the water temperature has been rising rapidly, when the internal pressure reaches a certain degree, the boiling water suddenly overflows, indicating that the main valve is stuck and suddenly opened.
When the water temperature gauge indicates 70 ℃ - 80 ℃, open the radiator cover and radiator drain switch, feel the water temperature with your hand. If it is hot, it indicates that the thermostat works normally; If the water temperature at the water inlet of the radiator is low, and there is no water outflow or little water flow at the water inlet pipe of the radiator upper water chamber, it indicates that the main valve of the thermostat cannot be opened.
The thermostat that is stuck or not tightly closed shall be removed for cleaning or repair, and shall not be used.
