Fault detection and maintenance of hydraulic torque converters

The common faults of hydraulic torque converters mainly include five types: excessively high oil temperature, insufficient oil supply pressure, oil leakage, too low machine traveling speed or weak driving force, and abnormal internal noises during operation.

The oil temperature is too high

Excessively high oil temperature is manifested as the oil temperature gauge exceeding 120°C during machine operation or feeling hot when touched by hand. The main reasons are as follows: The oil level in the transmission is too low; The water level in the cooling system is too low. The oil pipes and coolers are clogged or too dirty. The torque converter operates for too long within the low-efficiency range. The fastening screws of the working wheel are loose. Loose or damaged bearing fit; The combined hydraulic torque converter was locked due to the free wheel getting stuck. When assembling the guide wheel, the free wheel mechanism was missing parts.

The diagnosis and elimination methods for the fault of excessively high oil temperature in the hydraulic torque converter are as follows: When the oil temperature is too high, the engine should be stopped immediately, let it idle, and check if there is any leakage in the cooling system and whether the radiator is filled with water. If the cooling system is normal, the transmission oil level should be checked to see if it is between the two marks on the dipstick. If the oil level is too low, the same grade of oil should be replenished. If the oil level is too high, the oil must be drained to an appropriate level. If the oil level meets the requirements, the machine should be adjusted to ensure that the torque converter operates within the high-efficiency zone and to avoid prolonged operation in the low-efficiency zone as much as possible. If the oil temperature is still too high after adjusting the machine's working condition, the temperature of the oil pipe and the cooler should be checked. If the temperature is low when touched by hand, it indicates that the oil drain pipe or the cooler is clogged or too dirty. The oil drain pipe should be removed to check if there is any sediment blocking it. If there is sediment, it should be removed, and then the joint and the oil drain pipe should be reinstalled and sealed. If the temperature feels very high when touching the cooler, a small amount of oil should be drained from the torque converter housing for inspection. If there is metal dust in the oil, it indicates that the bearing is loose or damaged, causing the working wheel to wear. It should be disassembled, the bearing replaced, and the fastening bolts between the pump wheel and the pump wheel hub checked for looseness. If they are loose, they should be tightened. When all the above inspection items are normal but the oil temperature is still high, it is necessary to check whether the guide wheel is working properly. Fully open the engine throttle to put the hydraulic torque converter in zero-speed condition. When the oil temperature at the outlet of the hydraulic torque converter rises to a certain value, switch the hydraulic torque converter into the hydraulic coupling condition to observe the extent of the oil temperature drop. If the oil temperature drops very slowly, it may be due to the free wheel being stuck, causing the guide wheel to be locked. The hydraulic torque converter should be disassembled for inspection.

2. Low fuel supply pressure

The phenomenon is that when the engine throttle is fully open, the inlet oil pressure of the torque converter is still lower than the standard value. It is mainly caused by the following reasons: insufficient fuel supply and oil level lower than the suction port plane; Oil pipe leakage or blockage; There is too much oil flowing into the transmission. The oil inlet pipe or the oil filter screen is clogged. The hydraulic pump is severely worn or damaged. Improper installation of the oil suction filter screen; The oil foams. The inlet and outlet pressure valves cannot be closed or the spring stiffness is reduced.

If the oil supply pressure is too low, the oil level should be checked first. If the oil level is lower than the minimum mark, oil should be replenished. If the oil level is normal, check whether there is any leakage in the inlet and outlet oil pipes. If there is any oil leakage, it should be eliminated. If the inlet and outlet pipes are well sealed, the working conditions of the inlet and outlet pressure valves should be checked. If the inlet and outlet pressure valves cannot be closed, they should be removed to check whether there are cracks or scratches on the parts, whether the oil passage and oil holes are unobstructed, and whether the spring stiffness has decreased. Any problems found should be solved in a timely manner. If the pressure valve is functioning properly, the oil pipe or filter screen should be removed for inspection. If there is any blockage, it should be cleaned and the sediment removed. If the oil pipe is unobstructed, the hydraulic pump needs to be inspected and replaced if necessary. If the hydraulic oil foams, the installation of the return oil pipe should be checked. If the oil level in the return oil pipe is lower than that in the oil pool, the return oil pipe should be reinstalled.

3. The torque converter is leaking oil

The oil leakage of the torque converter is mainly caused by the loosening of the connecting bolts between the rear cover of the torque converter and the mating surface of the pump wheel, or the mating surface of the pump wheel and the hub, or the aging or damage of the sealing parts. If oil leakage is found, start the engine and check the leaking part. If oil leaks from the connection between the torque converter and the engine, it indicates that the connecting bolts between the pump wheel and the pump wheel cover are loose or the sealing ring is aged. The connecting bolts should be tightened or the O-ring should be replaced. If oil is flung from the connection between the torque converter and the transmission, it indicates that the connecting bolts between the pump wheel and the pump hub are loose or the sealing ring is damaged. The bolts should be tightened or the sealing ring inspected. If the oil leakage occurs at the oil filling port or the oil drain port, the tightness of the bolt connection and whether there are any cracks should be checked.

4. The machine's running speed is irregularly low or it runs weakly

This kind of malfunction is mainly caused by the following reasons: the internal sealing parts of the hydraulic torque converter are damaged, resulting in a decrease in the impact of the fluid flow in the working chamber; The free wheel mechanism is stuck, causing the guide wheel to be locked. The free wheel has worn out and failed. The blades of the working wheel are damaged. The inlet and outlet pressure valves are damaged. The hydraulic pump is worn out and the oil supply is insufficient. The hydraulic oil level is too low. The friction-type main clutch of the transmission is faulty.

After the machine starts in gear shifting, if it moves weakly or slowly, first check whether the indicated pressure on the gear shifting pressure gauge is within the normal range. If the pressure is too low, it should be eliminated. If the pressure is normal, it might be that the free wheel has worn out and failed or the working wheel blades have been damaged. It could also be that there is a fault with the friction clutch of the transmission. A specific analysis should be conducted and the problem should be eliminated.

5. There is an abnormal noise when the hydraulic torque converter is working

This kind of malfunction is mainly caused by reasons such as bearing damage, loose connection of the working wheel or loose connection with the engine. When this situation occurs, first check whether each connected production part is loose, and then inspect each bearing. If there is any looseness, adjust or replace the bearing with a new one. In addition, the quantity and quality of the hydraulic oil should be checked, and new oil should be added or replaced if necessary.