STEERING HYDRAULIC SYSTEM
Malfunction Analysis and Troubleshooting of Sinoteng wheel loader, forklift loader and log loader steering hydraulic system.
1. Heavy steering
① Normal at slow rotation of steering wheel, but heavy at fast rotation
a. Air in the system. When the oil level is low, the return of oil will bring in a large amount of air. In such case, add the oil timely. It may further rotate the steering wheel after rotating to limit position to open the overflow valve and drain the air.
b. Insufficient control pressure of priority valve and lowered spring force. Check the spring for damage or excessive compression set of spring and replace the spring timely.
c. The priority valve core is blocked at certain position. Disassemble the valve core, clean the parts such as valve body, and grind the valve core and valve body together. Make sure that the valve core moves smoothly in valve body.
d. Damage or insufficient flow of oil pump. Repair or replace accordingly.
② Light under unloaded status, but heavy under loaded status.
a. Low regulated pressure of steering overflow valve. Check the spring for damage or excessive compression set and replace accordingly. 2) Loose lock nut and pressure regulating bolt. Re-regulate the pressure and lock the lock nut.
b. Sealing failure of overflow valve and defect in sealing surface of valve core or valve seat. Repair accordingly.
c. Low cushion valve pressure in valve block. Check the spring for damage or excessive compression set or check sealing surface for sealing failure and replace the spring or repair accordingly.
d. Damage or insufficient flow of oil pump. Repair or replace accordingly.
③ Heavy steering at light accelerator, but normal at heavy accelerator.
a. Damage or insufficient flow of oil pump. Repair or replace accordingly.
b. Excessive fit gap between valve core and valve body of priority valve. Replace valve core or assembly accordingly.
2. No limit feeling at rotation and light rotation of steering wheel after rotating to limit position.
① Serious wearing and excessive gap of steering valve body, valve core, valve sleeve or stator/roller. Replace the worn-out parts or steering valve.
② Low opening pressure of overflow valve or cushion valve. The solution is same with above.
3. Steering failure
① Failure of automatic return of steering wheel and breakage of spring piece. Replace accordingly.
② Clear pressure tremble or even rotation failure. The pin or coupler shaft is damaged and shall be replaced.
③ Thorough damage of oil pump or shear-off of square key. Repair or replace.
4. Occasional action of hydraulic cylinder at rotation of steering wheel, with irregular noise.
This may be caused by the air in the steering system or excessive internal leakage of steering hydraulic cylinder. Open the oil tank cap and observe the oil tank for presence of foams. If yes, check oil tank for air leakage, check various pipeline connectors for intactness, and bleed the air from system. If the hydraulic cylinder only functions occasionally, check the sealing status of piston and replace seals when necessary.
5. If the steering wheel rotates by itself or swings left-and-right, this may be caused by the inverse installation between rotor and drive rod.
In such case, disassemble the steering valve and engage the tooth of drive rod with the tooth of roller spline hole, punch point to punch point.
6.Sudden feeling of heavy steering or rotation failure of steering wheel. Cause analysis and troubleshooting:
(1) Insufficient oil suction. Insufficient oil in oil tank, excessive oil viscosity, or blockage of oil suction filter will lead to the oil suction failure of the oil pump. In such case, check the oil level in the oil tank, add enough hydraulic oil, replace with proper oil, and clean or replace filter core.
(2) Excessive wearing and excessive internal leakage of oil pump. Check the working status of oil pump and repair or replace.
(3) If the steering check valve is not installed, the impurity lifts the steel ball of check valve to cause poor sealing with valve seat, or the steel ball of check valve drops into groove ring between valve sleeve and valve body, these will lead to poor sealing of check valve and interconnection between oil inlet and oil outlet during steering. In such case, check the installation status of check valve, check the oil cleanliness, and clean the steering valve. Check the sealing status between check valve steel ball and valve seat. In event of poor sealing, repair by grinding and replace with new steel ball.
(4) Failure and early opening of steering valve safety valve. Check the safety valve spring for deformation or failure. In event of insufficient spring force, add gasket between spring and spring seat.
(5) The deformations of valve core and the valve sleeve will lead to the blockage of both parts. Before installation, add some hydraulic oil via oil inlet. The rotation of valve core shall be smooth. In event of any stagnation, grind the valve core. Sometimes, the non-uniform application of force while tightening the bolts at bottom of steering gear will lead to blockage of valve core. The correct way is to tighten the bolts uniformly by 2~3 times.
7. Serious vibration of steering wheels. Cause analysis and troubleshooting:
(1) Mechanical malfunction. Such as the increased gap due to wearing between connecting pins or the wearing at bearings of steering wheels. In such case, check the gap and replace the parts to restore the normal working status of the system.
(2) Air in steering cylinder. In such case, loosen the oil port connector at one end of steering cylinder, rotate the steering wheel so that the oil flows via steering gear to the chamber at another end of steering cylinder, till the oil flowing out from the loose connector is free of air bubbles, and then tighten the connector.
8. The steering wheel can rotate without any limit, but steering wheels have no movement. Cause analysis and troubleshooting:
This is mainly caused by the failure of dual-directional cushion valve or the damage of hydraulic cylinder piston seal ring. Replace the hydraulic cylinder piston seal ring and check the dual-directional cushion valve to guarantee the close fit between valve core and valve seat.
