Inspection and troubleshooting of abnormal water temperature of domestic forklift
After a CPC3L forklift has been running for more than two years, the engine water temperature is abnormal. After the cold car is started, the water temperature rises rapidly and appears to boil within a short period of time. It returns to normal after the cooling water is added. After a detailed inspection of the cooling system (during which the water pump, thermostat, and fan belt were successively replaced), no obvious faults were found. Finally, the engine was disassembled and inspected, and it was found that the third cylinder liner had a 25mm long crack. After replacing the cylinder liner, the fault was eliminated.
The cooling system of domestic forklifts is relatively simple in structure, generally composed of cooling fans, radiators, thermostats and other components. The cooling fan is often driven directly by the engine, and the fan speed is consistent with the engine speed. The cooling water temperature control mainly depends on the thermostat. This is a big difference from the electronic fans controlled by temperature sensors and radiators with adjustable shutters used in ordinary cars. This structure is characterized by easy maintenance and low cost.
The disadvantage is that it is not sensitive to the cooling water temperature control. The level of the engine water temperature is mainly related to whether the thermostat is working properly, whether the water pump can establish sufficient pressure, and whether the cooling fan can reach the standard speed. Judging the failure of the cooling system should also start with judging whether these components work normally.
1. Inspection of thermostat
The thermostats currently used on engines are mainly wax thermostats. Its main performance index is that the thermostat should have different lifts at different water temperatures. Thus, the temperature of the cooling water is dynamically controlled. For the cooling system that does not disintegrate to check the quality of the thermostat, it is mainly judged by the temperature difference between the inlet and outlet pipes of the radiator. During the early period of engine cold start, the temperature difference between the inlet and outlet pipes should be obvious when touched by hand. After working for a period of time, the temperature difference will be significantly reduced. When the engine reaches the normal operating temperature (80℃-90℃), there is no obvious difference in temperature when touched 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 valve opening temperature and valve lift.
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 establish enough pressure is the key to the normal operation of the cooling system. When adding cooling water, if the engine speed increases, the cooling liquid level drops significantly, which indicates that the water pump works normally. On the contrary, the pump may be loosened from the impeller, and the cooling water cannot be circulated. In the domestic forklift engine, 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 of the belt with your fingers. The deflection should be normal at 11-13mm (CPC3L models). If it is too large, the water temperature will be too high, and if it is too small, it will damage the pump bearings and generator bearings.
3. Cooling fan
The detection of fan air volume can put a thin paper in front of the radiator. When the engine is running, if the paper can be blown open, it means that the air volume is sufficient. This is different from the inward suction of the car fan of the front engine. The blades cannot be reversed, and should ensure that the fan guard is complete and effective.
4. Radiator
The radiator of the forklift is placed at the rear of the vehicle. Due to the lower chassis of the forklift and the poor operating environment in the factory, some debris and dust are easily accumulated on the surface of the radiator. If it is not cleaned in time, it will seriously affect the heat dissipation effect. After the daily work, the radiator surface should be carefully cleaned, and the use of high-pressure water guns should be avoided as much as possible. Because the wall of the radiator is very thin, it is easy to collapse if the cleaning pressure is too high, which affects the circulation effect. In addition, the use of "hard water" for cooling water is strictly prohibited to prevent scale formation in the radiator, resulting in insufficient cooling water addition.
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 deposit in the combustion chamber, whether the injection time of the diesel engine is too early or too late, whether the cylinder gasket is burnt out, or whether the cylinder block and cylinder liner are cracked. As listed at the beginning of this article,
It is because of cracks in the cylinder liner, so that high-pressure gas enters the water jacket and intense bubbles appear, as if the cooling water is boiling. In short, the failures of the engine cooling system are various, but as long as you keep a clear mind and carefully analyze the essence of the problem, you can still find a solution.
