During the operation of a car, the engine combustion generates a large amount of heat, but the engine temperature should not be too high, otherwise problems such as cracking and deformation, poor oil lubrication, and increased wear may occur, resulting in a shortened service life of the engine. So it is important to cool down the engine. There are many cooling water circulation channels in the engine cylinder block. A water pump is installed at the engine's inlet, which is driven by a fan belt to pump out hot water and cold water from the channels, keeping the engine within a certain temperature range. The engine cooling water circulation generally has two cycles: small cycle and large cycle. When the car is first started, it is in a small cycle state, allowing the engine to heat up to around 80 degrees as soon as possible (the set temperature value varies depending on the model). When the thermostat is turned on, the car's cooling system enters a large cycle, rapidly cooling the engine coolant through the water tank and radiator to prevent the engine from overheating and malfunctioning. The water pump plays a key role in this process. When there is a problem with the water pump, it will affect the normal operation of the cooling system. Generally speaking, if the water pump is broken, there are the following symptoms: 1. Idle speed problem. The car water pump is connected to a belt to draw cold water from the water tank to cool the engine. If there is a problem with the rotation of the water pump, it will directly affect the engine speed, and the problem of unstable vehicle speed will be manifested. This phenomenon is usually manifested as the speed jumping and instability after the car starts. If the resistance is high, it may even cause the engine to stall. 2. Water pump leakage is a common fault, mainly due to inadequate sealing and engine leakage near the water pump. Leakage of coolant will leave traces of coolant color on the ventilation holes of the water pump, leading to symptoms such as high water temperature after lack of coolant. At the same time, when coolant leaks onto the bearings of the water pump, it will wash away the lubricant on the bearings, causing wear and damage to the bearings. 3. If obvious noise is observed in the car water pump during normal operation, it is likely that the water pump has started to be damaged, and the cause of the noise is the damage of the internal bearings or the loosening of the impeller, which is caused by the noise phenomenon of detachment from the shaft.