In our daily lives, small loaders are widely used, but malfunctions are inevitable. If a small loader fails to move or moves weakly in any gear, the fault can be narrowed down to the torque converter, travel pump, pressure reducing valve, and other common oil circuits and components for each gear. When this type of fault occurs, the main drive shaft will not rotate when the machine is not moving.
For this type of fault, first check if the hydraulic oil level in the transmission is sufficient. The method is to keep the engine at idle and observe the oil level; it should be in the middle of the oil level indicator on the side of the transmission. If the oil level is not visible, add oil promptly. After the oil level is normal, determine whether the fault appeared suddenly or gradually. If it is a sudden fault, disassemble and inspect the pressure reducing valve to see if it is dirty, if the valve core is scratched, or if it is stuck at the minimum oil supply position. This can be resolved by cleaning and grinding. Then check if the spline of the travel pump connection sleeve is damaged. If the fault symptoms appear slowly, it is generally due to gradual wear of the travel system components or poor oil cleanliness. Check in the following order:
(1) Determine if the fault is in the torque converter. Inspect the hydraulic oil return filter mounted on the rear rack. If a large amount of aluminum dust adheres to the filter screen, it indicates that the bearing inside the torque converter is damaged, causing wear on the three wheels. The torque converter should be disassembled, the damaged parts replaced, and the oil circuit cleaned.
During operation, the transmission oil in the torque converter's working oil chamber must be kept full. Insufficient oil will lead to a decrease in output torque, causing the main drive shaft to rotate weakly or stop rotating. During inspection, disconnect the low-pressure hose for the torque converter's return oil (torque converter overflow) to the transmission and observe the overflow flow rate of the return oil hose at engine idle. Under normal conditions, there is only a small flow rate. As the engine speed increases, the flow rate will suddenly increase when the overflow valve in the torque converter's pressure reducing valve suddenly opens. If this flow rate is also large at engine idle, it can be determined that the sealing ring inside the torque converter is severely worn, causing internal leakage.
(2) If the torque converter's return oil to the transmission is normal, run the engine at high speed. If the return oil volume is small, check whether there is dirt blockage or air leakage in the oil suction line of the travel pump. The main checks include inspecting the oil suction filter installed in the gearbox and whether the travel pump hose is aging, internally detached, or bent.
(3) If the above are normal, it can be determined that the travel pump has low volumetric efficiency, and the travel pump should be replaced.
(4) A lack of travel power is generally not considered a problem with the torque converter's oil return cooling circuit.
Drivers who frequently operate small loaders will inevitably encounter various malfunctions. This article introduces some of these malfunctions and their solutions, hoping to provide assistance to drivers.
