Inspection and repair of abnormal water temperatur

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Inspection and repair of abnormal water temperature of domestic forklifts

a c2.1 sensor design pc3l forklift has abnormal engine water temperature after running for more than two years. After the cold start, the water temperature rises rapidly and boils in a short time, and it returns to normal after adding cooling water. After a detailed inspection of the cooling system (during which the water pump, thermostat and fan belt were replaced successively), no obvious fault was found. Finally, the engine was disassembled and inspected, and a 25mm long crack was found on the cylinder liner of the third cylinder. After replacing the cylinder liner, the fault was eliminated

the cooling system of domestic forklift truck is relatively simple in structure, which is generally composed of cooling fan, radiator, thermostat and other components. The cooling fan is often driven directly by the engine, and the fan speed is consistent with the engine speed. The control of cooling water temperature mainly depends on thermostat. This is quite different from the electronic fan controlled by temperature sensor and the radiator with adjustable shutter used in ordinary cars. This structure is characterized by convenient maintenance and low cost. The disadvantage is that the control of cooling water temperature is not sensitive. The water temperature of the engine is mainly related to whether the thermostat works normally, whether the water pump can establish sufficient pressure, and whether the cooling fan can reach the standard speed. To judge the failure of the cooling system, we should also judge whether these components work normally

1. Inspection of thermostat

at present, the thermostat used on the engine is mainly wax thermostat. Its main performance index is that the thermostat should have different lift under different water temperatures. Thus, the cooling water temperature can be dynamically controlled. For checking the thermostat without disassembling the cooling system, it is mainly judged by the temperature difference between the radiator inlet pipe and outlet pipe. There should be a significant temperature difference between the inlet and outlet pipes when touched by hand during the early period of engine cold start. After working for a period of time, the temperature difference is significantly reduced. When the engine reaches the normal operating temperature (80 ℃ -90 ℃), there is no obvious temperature difference when touching it with your hand. Of course, the most accurate detection method is to remove the thermostat, place it in hot water, gradually heat it, and check the opening temperature and lift of the valve

2. Inspection of water pump

the power source of continuous circulation of cooling water in the cooling system comes from the water pump. Whether the water pump can establish sufficient pressure is the key to the normal operation of the cooling system. When adding cooling water, if the cooling level drops significantly with the increase of engine speed, it indicates that the water pump works normally. Otherwise, the water pump and impeller may be loose and the cooling water cannot be circulated. In domestic forklift engines, the water pump, generator and cooling fan share a belt, so the tightness of the belt directly affects the speed of the water pump, fan and generator. Press the middle of the belt with your fingers, and the lower deflection should be mm (cpc3l model). Too much will lead to too high water temperature, and too small will cause damage to the water pump bearings and generator bearings

3. Cooling fan

fan air volume detection can put a thin paper in front of the radiator. When the engine is running, pay attention to the following aspects to stop protection and maintenance: all parts of the experimental machine should be wiped clean frequently. If the paper can be blown away, it means that the air volume is sufficient. This is different from the inward suction of the car fan with the front engine. The blades shall not be installed reversely, and the fan cover shall be complete and effective

4. Radiator

the radiator of the forklift is placed at the rear of the vehicle. Due to the low chassis of the forklift and the poor working environment in the factory, some sundries and dust are easy to accumulate on the surface of the radiator. If they are not cleaned in time, the heat dissipation effect will be seriously affected. After daily operation, the surface of the radiator should be carefully cleaned, and the use of high-pressure water guns should be avoided as far as possible. Because the tube wall of the radiator is very thin, if the cleaning pressure is too high, it is easy to shrink and affect the circulation effect. In addition, it is strictly forbidden to use "hard water" in the cooling water to prevent scaling in the radiator, resulting in insufficient cooling water

after checking the above main components and judging that there is no obvious fault, the problems of other systems should be considered. For example, whether there is too much carbon deposition in the combustion chamber, whether the injection time of the diesel engine is too early or too late, whether the cylinder gasket is burned out, or whether the cylinder block and cylinder liner have cracks. For example, the faults listed at the beginning of this article are: 1. The conical rib connection and ribbed steel bar connection are due to cracks in the cylinder liner, which makes the high-pressure gas rush into the water jacket and emit fierce bubbles, like the boiling of cooling water. In short, the faults of engine cooling system are various, but as long as we keep a clear mind and carefully analyze the essence of the problem, we can still find a solution and set up utilization technology research centers and industrialization centers in Shanghai and Huaibei

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