The pump is one of the important parts of the engine cooling system. The function of the pump is to pressurize the coolant to ensure that it circulates in the cooling system to accelerate the emission of heat. As a long-term running device, the pump will also fail during the operation. How can we repair these failures? 1, check whether the pump body and pulley wear and damage, if necessary, should be replaced. Check whether there is any bending of the pump shaft, the wear degree of the journal, and whether there is any damage to the shaft end thread. Check whether the blades on the impeller are broken and the wear of shaft holes is serious. Check the wear degree of water seal and bakelite gasket, for example, new parts should be replaced if exceeding the limit of use. Check the wear condition of the bearing and use the meter to measure the clearance of the bearing. If more than 0.10mm, the new bearing should be replaced. 2, after the pump is removed, it can be decomposed sequentially. After decomposing, the parts should be cleaned and checked one by one to see if there are any defects such as cracks, damage and wear. If serious defects are found, they should be replaced. 3, water seal and seat repair: water seal, such as worn slots, can be grinded with sand cloth, such as wear and tear should be replaced; water seal, such as a rough scratch, can be repaired by a flat reamer or on a lathe. A new water seal should be replaced during overhaul. 4, when the pump body has the following damage, the welding repair is allowed: the length is within 30mm, the crack is not stretched to the bearing seat hole; the flange joint with the cylinder head has a broken part; the oil seal hole is damaged. The bending of the pump shaft should not exceed 0.05mm, otherwise it should be replaced. The blade breakage of the impeller should be replaced. The wear of the shaft diameter of the pump shaft should be changed or repaired. 5. Check whether the bearing of the pump is flexible or abnormal. If there is any indication that the bearing is defective, it should be replaced. 6, after the pump is assembled, rotate it with your hands. The pump shaft should be free from stagnation, and the impeller and pump shell should not be rubbed. Then check the displacement of the pump. If there are any problems, check the cause and exclude. If the pump fails, the coolant will not be able to reach the corresponding place, its performance will not be effectively played, and ultimately affect the work of the engine. Therefore, it is necessary to strengthen the inspection of the water pump.