1) Fault phenomenon
After the loader has been working for a long time, the temperature of the working oil of the torque-converter hydraulic system is reflected on the oil temperature gauge at a value of 80~95℃, and the housing of the torque converter and the transmission does not feel particularly hot when touched by hand. If the temperature displayed on the oil temperature gauge exceeds 100℃ and is close to 120℃, or the housing of the torque converter and the transmission feels particularly hot when touched by hand, the oil temperature of the torque-converter hydraulic system is too high. If the oil temperature of the system is too high, the sealing parts will age easily, the working oil will become thinner, and the pressure of the system will drop. Such a vicious cycle will shorten the service life of the loader. Even if it does not affect the operation of the loader temporarily, the fault must be eliminated as soon as possible.
(2) Fault cause and elimination
1 The diesel engine has not started for a long time, the speed is not high, the transmission is not running in neutral, and the system oil pressure is normal, but the oil temperature rises quickly.
a. When the diesel engine is started and in neutral, the power output shaft of the torque converter should rotate even in the idle state. If the output shaft does not rotate, it means that the transmission efficiency of the torque converter is low and the input power is converted into heat. The torque converter is not working properly. The main reasons and troubleshooting methods are as follows.
i. The pressure of the inlet pressure valve or outlet pressure valve is abnormal. The pressure of the inlet pressure valve and outlet pressure valve on the triple valve is not displayed by a pressure gauge, but only the pressure detection port is set to detect. Under normal circumstances, the inlet pressure is 0.64MPa and the outlet pressure is 0.25MPa. If there is a problem inside the valve, such as spring breakage, spring softening, valve core jamming, etc., it is possible that the system pressure is not suitable, and the triple valve needs to be disassembled for inspection and repair.
If the pressure of the inlet and outlet pressure valves is not suitable and needs to be adjusted, a pressure gauge should be connected. Without a pressure gauge, the pressure cannot be adjusted to a qualified level by trial adjustment based on feeling. If you only try to adjust, remember the original position of several adjustment screws (that is, the height of the head of the adjustment screw above the valve body). If the adjustment screw is turned in 1~2 turns, the working condition of the torque converter does not change at all, and the adjustment screw should be screwed back to the original position.
II There is mechanical friction inside the torque converter. When the torque converter is working, there is a certain gap between the working wheels (pump wheel, turbine wheel, guide wheel), and they do not contact or rub each other when rotating. If the bearing is severely worn, the working wheel blades are broken, or the rivets or screws fall off, abnormal friction and wear will occur between the working wheels, resulting in an increase in the working oil temperature.
If the oil temperature rises due to the above reasons, after the diesel engine is turned off, remove the connecting bolts of the first transmission shaft and the transmission input shaft, and turn the first transmission shaft by hand. You will feel obvious resistance, and a large amount of silver-white aluminum alloy powder will be found on the filter screen of the oil pan of the transmission. The released oil is silver-white. In this case, the torque converter should be overhauled, all damaged parts should be replaced, and the gear shift clutch should be properly assembled as required.
b. The gear shift clutch is not completely separated. If the torque converter works normally, but a gear shift clutch of the transmission feels hot when touched by hand, it means that the clutch of the gear is not completely separated. When not in gear, there should be no large friction between the active friction plate and the driven friction plate, and even relative movement will not generate too much heat. If the active friction plate and the driven friction plate are severely deformed, the disc return spring does not return to its position, and there are large impurities between the friction plates, the clutch of a certain gear will not be completely separated. Troubleshooting method: disassemble and repair the shift clutch.
2 The loader has not been running and operating for a long time, but the housing of the torque converter and the transmission feels particularly hot when touched.
a. The system oil pressure is normal, but the operation or driving is weak, and the housing of the torque converter feels higher than the housing of the transmission when touched. The reason is often that the guide wheel of the torque converter is stuck. If the guide wheel of the torque converter is stuck, the torque converter needs to be disassembled and repaired.
i. If the inner and outer raceways are not smooth, deformed, and have pits and other serious wear, the one-way clutch subassembly should be replaced.
ii. The spring in the roller top sleeve of the one-way clutch cannot return due to sludge clogging. The working oil should be replaced and the system should be cleaned.
iii. The roller spring of the one-way clutch becomes soft, which will also cause the guide wheel to get stuck. The spring should be replaced.
b. The hydraulic system oil pressure is too low, causing the transmission's gear clutch master and slave friction plates to slip during operation, causing heat. The specific causes, judgments and solutions should be analyzed with reference to the hydraulic system oil pressure failure, and the hydraulic system oil pressure failure should be eliminated first.
3 The thermal balance system is not working properly. The failure of the temperature sensor of the thermal balance system, the failure of the calculation module of the thermal balance system, and the poor operation of the oil pump and motor will also cause the torque conversion hydraulic system oil temperature to be high.
If the thermal balance system is not working properly, the temperature of each cooling system that needs to dissipate heat will be high. 4 Long-term driving and operation.
a. The radiator has poor heat dissipation effect. The working oil of the torque conversion transmission is cooled and dissipated through the radiator. If the radiator is clogged with sludge, the heat dissipation pipe is deformed, and the outside of the heat dissipation pipe is covered with dust, the heat dissipation effect will be poor, and the working oil temperature of the torque conversion transmission will also be high.
b. High ambient temperature and long continuous operation time. In hot areas, when the summer temperature is above 40℃, continuous operation for more than 3~4 hours and high-intensity operation of the loader will make the oil temperature of the system relatively high. In this case, the operation should be stopped to cool down.