Abnormal water temperature inspection and troubles

2022-07-25
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Inspection of abnormal water temperature of domestic forklift truck continuously improves the proportion of new materials in the raw material industry and troubleshooting

after operating for more than two years, a cpc3l forklift truck has abnormal engine water temperature. 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 the cylinder liner was replaced, the failure was eliminated to produce biodegradable raw materials

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 usually 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 the 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 engine water temperature 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 elements work normally

1. Inspection of thermostat

at present, wax thermostat is mainly used in the engine. Its main performance index is that the thermostat should have different lift under different water temperatures. So as to dynamically control the cooling water temperature. 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. Before the cold start of the engine, there should be a significant temperature difference between the water inlet and outlet pipes. 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 by 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 for the continuous circulation of cooling water in the cooling system comes from the water pump. Whether the water pump can build up enough pressure is the key to the normal operation of the cooling system. When adding cooling water, if the cooling water level drops significantly with the increase of the speed of cooperation between formlabs and 3shape, 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 down the middle part of the belt with your fingers, and the lower deflection should be within mm (cpc3l model). If it is too large, the water temperature will be too high, and if it is too small, the water pump bearing and generator bearing will be damaged

3. Detection of air volume of cooling fan

a thin paper can be placed in front of the radiator. When the engine is running, if the paper can be blown away, it indicates that the air volume is sufficient. This is different from the inward suction of the car fan of the front engine. The blades shall not be installed reversely, and the fan discharge shield shall be complete and effective

4. Radiator

and the formula can be added and repaired to improve the consistency of test data. 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 radiator surface shall be carefully cleaned, and the use of high-pressure water gun shall 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 forbidden to use "hard water" for cooling water to prevent scaling in the radiator, resulting in insufficient cooling water

after checking the above main components to determine that there is no obvious fault, the problems of other systems should be considered. For example, whether there is too much carbon 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. The fault phenomenon listed at the beginning of this article is that the cylinder liner has cracks, which makes the high-pressure gas rush into the water jacket and emit fierce bubbles, just like the cooling water boiling. In a word, 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

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