Doosan D20G, Service Manual

Page: 896 / 1209

Vehicle System Testing and Adjusting 38
Problem: Foreign material behind the wiper
rings causing scratches on the cylinder rod.
Probable Cause:
1. The wiper rings show wear and do not remove dirt
and foreign material.
Steering System
Problem: Too much force needed to turn
steering wheel.
Probable Cause:
1.
Priority valve releases pressure oil at a low setting.
2. Pump oil pressure is low, worn pump.
3. Steering gear covers are too tight.
4. Steering column not aligned with steering gear.
5. Priority valve spool is held in one position.
6. Steering gear without lubrication.
7. Low fluid level in the hydraulic supply tank.
8. Steer axle damaged.
9. Worn steer cylinder piston seal.
Problem: Steering wheel does not return to
center position correctly.
Probable Cause:
1.
Steering gear covers are too tight.
2. Steering column is not in correct alignment.
3. Valve spool in the steering gear has a restriction.
4. Priority valve check valve permits lift and tilt
hydraulic oil to affect steering hydraulic circuit.
Problem: Oil leakage at the pump.
Probable Cause:
1. Loose hose connections.
2. Detective shaft seal.
Problem: Low oil pressure.
Probable Cause:
1.
Low oil level.
2. Priority valve relief valve spring weak.
3. Relief valve (priority valve) will not move from the
open position.
4. Oil leakage inside or outside of the system.
5. Defective pump.
Problem: Pump makes noise and the steering
cylinder rod does not move smoothly.
Probable Cause:
1.
Air in the steering hydraulic circuit.
2. The pump has too much wear.
3. Loose connection of the oil line on the inlet side of
the pump.
4. The viscosity of the oil is wrong.
5. The oil level in the hydraulic tank is low.
6. Worn steer cylinder piston seal.
Problem: Lift truck does not turn when steering
wheel is slowly turned
Probable Cause:
1.
The oil level of the tank is low.
2. There is air in the steering system.
3. The pump operation is not correct.
4. Dirt in the steering system.
5. Steering gear operation is not correct.
6. Steering cylinder has worn parts.
7. Restriction in the steer axle linkage.