Early car engines did not have an important attachment we now consider essential - the water pump, when the liquid cooling medium used was pure water, mixed with a little bit of wood alcohol at most to prevent icing. The circulation of cooling water depends entirely on the natural convection heat phenomenon. After the cooling water absorbs heat from the cylinder block, it naturally flows upward and enters the upper part of the radiator. After the cooling water cools down, it naturally sinks to the bottom of the radiator and enters the lower part of the cylinder block. The use of this principle of thermosyphon can barely complete the task of cooling. But soon after, pumps were added to the cooling system to allow the cooling water to flow more quickly. Modern automotive engine cooling systems are generally used centrifugal pumps. The most plausible installation of the pump is at the bottom of the cooling system, but most of the pumps are located in the middle of the cooling system and a few of the pumps are located on the top of the engine. Pumps placed on the top of the engine are prone to cavitation. No matter in what position, the pump pumps a lot of water, such as a V8 engine pump pump water, idling about 750L / h, to about 12000L / h at high speed. From the service life point of view, the biggest change in the design of the pump was the appearance of ceramic seals a few years ago, which is more wear-resistant than the previously used rubber seals or leather seals, but it also has easy Disadvantages of being scratched by hard particles in the cooling water. Although the pump seal to prevent the failure of the design has been continuously improved, but so far can not guarantee the pump seal is not a problem. Once the seal leaks, then the pump bearing lubrication will be washed away. Troubleshooting In the past 20 years, the durability of the car has been greatly improved, then the service life of the pump is longer than it used to be? not necessarily. Today's pumps still need a lot of replacement work, the car about driving 100,000 km, the pump will have the possibility of failure at any time. Pump fault diagnosis is generally relatively simple. In the event of a leak in the cooling system, the smell of hot antifreeze can be heard, but a check must be made to see if the cooling water has escaped from the pump shaft seal. Use a small mirror and light to see if there is a leak in the pump vent. To be regularly maintained, pay attention to check the tank coolant loss. Leakage is the number one fault pump, noise is the second fault, due to bearing scratches caused by the shaft of the pump killed the phenomenon is very rare. Once this happens, wind and heat sinks get damaged. Although it is common to find in pump documentation serious corrosion of pump impellers, impeller corrosion is not a common occurrence if normal maintenance is done. When you see the coolant red, rusty color, it is estimated there is a problem of impeller corrosion. At this time you need to check the pump coolant circulation, the radiator can be part of the coolant, so that the water level just above the water pipe, and then preheat the engine so that the thermostat in a fully open position. When the engine speed is 3000r / min, you should see a good water cycle. Another possible problem is that the pump impeller appears loosely on the shaft.