1. The power steering feels heavy or lacks assistance

Symptoms:
Heavy steering, with brief loss of hydraulic power assistance

Causes of fault: 

① Loose V-belt on the oil pump 

② Oil level in the reservoir too low 

③ Insufficient oil pump pressure 

④ Pressure control valve sticking 

⑤ Excessive external leakage 

⑥ Excessive internal leakage 

⑦ Steering shaft bushing too tight 

⑧ Front suspension deformation 

⑨ Air in the hydraulic system

Troubleshooting: 

① Check the condition of the power steering pump drive assembly. Press down on the power steering pump drive belt by hand; if it compresses excessively, this indicates that the drive belt is too tight and needs adjusting. Start the engine and allow it to run at idle speed, then suddenly increase the engine speed to check whether the power steering pump drive belt slips. If slippage occurs, this indicates that the drive belt is too loose or excessively worn, and it should be adjusted or replaced.

② Check the level of the steering fluid in the reservoir. If the level is below the lower mark or the ‘MIN’ mark, this indicates that the steering fluid is low and should be topped up to the specified level.

③ Check the filter in the power steering fluid reservoir. Remove the filter and inspect the condition of the filter screen. If the filter screen is excessively dirty, this indicates that the filter is blocked and should be cleaned; if the filter screen is torn, it should be replaced.

④ Check for air in the system. First, start the engine and allow it to run at idle speed, then turn the steering wheel back and forth several times and observe the condition of the steering fluid. If the steering fluid is foamy or cloudy, this indicates that air has entered the steering system and must be bled out; check whether the steering oil pump’s inlet hose is cracked; if so, replace it; Check whether any of the pipe joints are loose; if so, tighten them; check whether the seal ring on the steering oil pump shaft is damaged; if there is an oil leak, replace it with a new part.

⑤ Check the oil pressure in the steering system. Connect a pressure gauge between the steering oil pump and the power steering unit, run the engine at idle, and close the pressure gauge valve. If the pressure does not reach the specified value within 10 seconds, this indicates insufficient pressure from the steering oil pump, which should be dismantled, inspected and repaired. Turn the steering wheel to its left or right limit position, open the pressure gauge valve; if the pressure does not reach the specified value, this indicates a fault with the power steering unit or that the valves are incorrectly adjusted, and it should be dismantled, inspected and adjusted.

2. The power steering system is making a noise

Symptoms:
A noise is heard coming from the power steering pump when the car is turned

Causes of failure:   

① Loose V-belt on the oil pump 

② Damaged oil pump bearings 

③ Damage to the pressure plate or rotor 

④ Excessive wear on the oil pump ring 

⑤ Insufficient oil in the reservoir 

⑥ Air in the hydraulic system or loose pressure hose connections 

⑦ Incorrect assembly of the oil pump 

⑧ Faulty relief valve

Troubleshooting: 

① Check the level of the steering fluid in the reservoir. If the level is below the lower mark or the ‘MIN’ mark, this indicates that the steering fluid level is too low; top up to the specified level. If the steering fluid is being consumed too quickly, this indicates a serious leak, which should be investigated and rectified.

② Check the condition of the power steering pump drive assembly. Press down on the power steering pump drive belt by hand; if it deflects too much, this indicates that the drive belt is too loose and should be adjusted.

③ Check for air in the power steering fluid. Open the reservoir cap, start the engine and let it run at idle speed, then turn the steering wheel back and forth several times to check for bubbles in the power steering fluid. If bubbles are present, this indicates that air has entered the power steering fluid and must be bled out.

④ Check whether the filter screen on the oil reservoir is blocked and whether the oil piping is correctly routed. Remove the filter screen from the oil reservoir; if it is excessively dirty, this indicates that the oil is not circulating properly and it should be cleaned; if the oil piping is kinked or dented, it should be replaced.

⑤ If all the above test results are correct, the steering oil pump should be dismantled and inspected to check for scratches on the vanes and the pump housing; replace the relevant parts as necessary based on the findings of the inspection.

3. The steering feels different on the left and right

Symptoms:
Whilst the vehicle is in motion, the steering effort required to turn left and right is not equal.

Causes of fault: 

① The spool (or slide valve) of the steering control valve is out of the centre position, or, although it is in the centre position, the clearance between it and the shoulder of the valve body is inconsistent;

② Debris inside the control valve is causing blockages, resulting in different levels of resistance when turning it to the left and right;

③ Air has entered one of the oil chambers of a power cylinder in the hydraulic system;

④ Oil leakage

Troubleshooting: 

This fault is usually caused by contaminated oil; replace the oil with fresh oil in accordance with the specifications before carrying out any checks.

① If the fault persists despite the oil being of good quality or having been replaced with fresh oil, the hydraulic system should be bled and checked for oil leaks. Should a leak be found in the hydraulic system, the components at the leak point should be replaced; 
 ② If the fault still cannot be rectified, it may be caused by poor centring of the control valve. Faults in spool-type steering control valves can be rectified externally to the power steering unit by adjusting the position of the valve body. If the fault persists after adjusting the spool position, the spool should be dismantled and inspected to measure its dimensions; if there is significant deviation, the spool should be replaced. For rotary-type steering control valves, the fault must be rectified by dismantling and inspecting the valve.