When the water temperature of Ruifeng vehicle reaches 90 degrees, the engine compartment makes a sneering sound, and then the water temperature drops and slowly disappears. What happened?

Hello! The coolant is boiling! There may be several reasons for the high water temperature. 1. The cooling fan does not rotate. The cooling fan can be controlled by a temperature control switch; It can also be controlled by a water temperature sensor. 2. Insufficient cooling medium. (1) antifreeze: high-end cars are required to be filled with antifreeze all year round; ② Water or distilled water: temporary substitution; ③ The water tank cover leaks. The thermostat is broken. (1) If the thermostat is to be removed, the small circulation should be blocked at this time to ensure that the coolant is completely dispersed by the water tank; (2) When installing a new thermostat, pay attention to the water hole, such as Santana, there is no water hole. At this time, a hole should be drilled with a 6mm drill. One function is used for marking; Another function is that when the car heats up, it will produce the temperature difference between the two sides of the thermostat, so that the thermostat can be opened accurately with the water temperature. The water tank is blocked. ① External blockage should be removed by water or gas; (2) Internal blockage will affect the circulation of coolant and generate pressure at the same time. At this time, there will be two results, one is that the water tank leaks, and the other is that the water temperature is particularly high when driving at high speed. 5. Pump failure. ① The timing belt is broken due to slipping or sticking of the impeller; ② Impeller deformation. 6. Cylinder corrosion. (1) When the combustion chamber collides with the waterway, it will drain water or discharge white smoke from the drain pipe, resulting in frequent water shortage in the water tank; (2) The waterway collides with the oil path (the oil with water is white); (3) The collision between waterways leads to poor heat dissipation of the cylinder block, especially at high speed; ④ The waterway is blocked.