【Troubleshooting Method】Causes of Slow Steering on Excavators

I. Check for external leakage in the hydraulic steering system

Major symptoms of external oil leakage include substantial hydraulic oil loss, reduced system pressure, and jerky movement of steering cylinders and motors. These lead to slow, weak steering or even complete loss of steering function. Main causes of external leakage: improper fitting of hose connectors, poor sealing or ruptured pipelines; ill-fitted, worn, aged or damaged seals; excessively high oil temperature which aggravates leakage. External oil leakage shall be repaired promptly once detected.

II. Inspect hydraulic oil

The quality and quantity of hydraulic oil directly affect the performance of the steering system. Insufficient hydraulic oil results in inadequate oil supply to the hydraulic pump and slow steering response of the machine. Top up hydraulic oil to the specified level. Contaminated hydraulic oil or foreign objects inside the oil tank will enter the hydraulic system, damaging seals and mating components and increasing internal leakage, which causes slow steering. The oil quality must be carefully inspected. Replace the hydraulic oil and clean the entire hydraulic system immediately if impurities are found.

III. Check if air has entered the hydraulic steering system

Even a small amount of air entering the hydraulic system can significantly impact performance, causing steering cylinder crawling, lowering hydraulic system efficiency and resulting in slow steering. Air may enter the hydraulic system through loose connectors or ruptured pipes on the steering pump suction line; poor sealing of the steering pump; excessively low oil level in the tank exposing suction or return lines above the oil surface; degraded hydraulic oil quality.

Inspection method: Start the engine and turn the steering wheel while observing the oil tank. If bubbles emerge in the tank, air has entered the hydraulic system. Identify and eliminate the root cause.

IV. Inspect the steering cylinder

Worn or damaged seals between the piston and cylinder barrel inside the steering cylinder increase internal leakage and slow down cylinder movement. Inspection method: Remove the steering cylinder and install it on another excavator with normal steering for testing. If steering works well after installation, the steering cylinder is intact. If steering remains slow, the cylinder seals are faulty. Disassemble the steering cylinder to check damage to pistons and seals, and scoring on the cylinder barrel, then perform repairs.

V. Inspect the steering pump

Severe internal leakage inside the steering pump also causes slow machine steering. A major cause of steering pump internal leakage is excessive clearance between the side faces of pump rotors/blades and the end faces of side plates (normal clearance ≤0.047 mm, maximum allowable value ≤0.100 mm). Inspection method: Carry out a comparative test by fitting a new pump, provided the steering cylinder, central swivel joint and steering control unit are in good condition. If steering performance returns to normal after pump replacement, the fault lies in the steering pump and a new pump shall be installed.

VI. Inspect the central swivel joint

Severe wear on the inner cylindrical surface or seals of the excavator central swivel joint causes cross-communication between oil and gas circuits at failed sealing points, resulting in sluggish operation of all circuits passing through the swivel joint. During steering, high-pressure oil leaks into the air circuit or other hydraulic lines (suspension, outriggers, etc.), reducing the oil supply to the steering cylinder and slowing its movement.

Inspection method: Pull up the manual air switch for wheel braking. If oil mist sprays out with the air, oil has leaked into the air circuit due to heavy wear of the central swivel joint. Replace the seals of the central swivel joint and repair the joint.

VII. Inspect the steering motor

Severe wear on the working surfaces of the steering motor stator and rotor, or the working surfaces of the rotary valve reduces the actual volume of high-pressure oil delivered to the steering cylinder and slows steering action. If the steering cylinder and central swivel joint function properly, turn the steering wheel to full lock with the engine shut down. If the front wheels deflect immediately without heavy resistance, the steering control unit is faulty and shall be repaired or replaced immediately.

VIII. Inspect the single-line flow stabilizing valve

Weakened spring force of the single-line flow stabilizing valve reduces the hydraulic pressure of the steering system, resulting in insufficient steering cylinder output and slow steering. Remedy: Remove the nylon plug at the remote control port on the valve base of the single-line flow stabilizing valve and fit a pressure gauge. Start the engine, turn the steering wheel to full lock left or right while placing a barrier beside the front wheel. Observe the pressure gauge reading. If pressure fails to reach 7 MPa, turn the adjusting screw of the flow stabilizing valve inward appropriately (loosen the lock nut first) to resolve the fault.