What is the reason why the water temperature of the car goes up and down?

The reasons why the water temperature of the car rises and falls are as follows: 1. Insufficient coolant: Starting long-term water circulation will lead to the slow loss of coolant in the engine cooling system, resulting in water shortage in the water tank. If the owner fails to check and add coolant in time, it is easy to cause the engine water temperature to be too high. 2, water tank leakage: water tank connecting pipe rupture or loose connection, will cause water leakage. At this time, the water circulation will be seriously blocked, causing the engine to "boil", that is, emit white smoke. 3. Failure of cooling fan: The cooling fan is damaged or the wire is short-circuited, which causes the fan to work or the cooling fan to rotate slowly, which will lead to the heat of the engine not being radiated and the water temperature of the engine naturally rises. 4. Thermostat failure: Thermostat is a device to control the flow path of coolant. Once it is stuck or fails, the cycle of the engine is bound to be affected, and the heat of the engine cannot be effectively dissipated.