Power cylinder performance check Figs 912 913

1 Connect the combined pressure gauge and shut-off valve tester between the pump and control valve as under pump output check.

2 Open shut-off valve, start and idle the engine and turn the steering from lock to lock to bleed out any trapped air.

3 Turn the steering onto left hand full lock. Hold the steering on full lock and check pressure reading which should be within 10% of the pump output pressure.

4 Turn the steering onto the opposite lock and again check the pump output pressure.

5 If the pressure difference between the pump output and the power cylinder on both locks is greater than 10% then the power cylinder is at fault and should be removed for inspection.

6 If the pressure is low on one lock only, this indicates that the reaction control valve is not fully closing in one direction.

A possible cause of uneven pressure is that the control valve is not centralizing or that there is an internal fault in the valve assembly.

Binding check A sticking or binding steering action when the steering is moved through a portion of a lock could be due to the following:

a) Binding of steering joint ball joints or control valve ball joint due to lack of lubrication. Inspect all steering joints for seizure and replace where necessary.

b) Binding of spool or rotary type control valve. Remove and inspect for burrs wear and damage.

Excessive free-play in the steering If when turning the driving steering wheel, the play before the steering road wheels taking up the response is excessive check the following;

1 worn steering track rod and drag link ball joints if fitted,

2 worn reaction control valve ball pin and cups,

3 loose reaction control valve location sleeve.

Heavy steering Heavy steering is experienced over the whole steering from lock to lock, whereas binding is normally only experienced over a portion of the front wheel steering movement. If the steering is heavy, inspect the following items:

1 External inspection — Check reservoir level and hose connections for leakage. Check for fan belt slippage or sheared pulley woodruff key and adjust or renew if necessary.

2 Pump output — Check pump output for low pressure. If pressure is below recommended maximum inspect pressure and flow control valves and their respective springs. If valve's assembly appears to be in good condition dismantle pump, examine and renew parts as necessary.

3 Control valve — If pump output is up to the manufacturer's specification dismantle the control valve. Examine the control valve spool or rotor and their respective bore. Deep scoring or scratches will allow internal leaks and cause heavy steering. Worn or damaged seals will also cause internal leakage.

4 Power cylinder — If the control valve assembly appears to be in good condition, the trouble is possibly due to excessive leakage in the power cylinder. If there is excessive internal power cylinder leakage, the inner tube and power piston ring may have to be renewed.

Noisy operation To identify source of noise, check the following:

1 Reservoir fluid level — Check the fluid level as a low level will permit air to be drawn into the system which then will cause the control valve and power cylinder to become noisy while operating.

2 Power unit — Worn pump components will cause noisy operation. Therefore dismantle and examine internal parts for wear or damage.

3 If the reservoir and pump are separately located, check the hose supply from the reservoir to pump for a blockage as this condition will cause air to be drawn into the system.

Steering chatter If the steering vibrates or chatters check the following:

1 power piston rod anchorage may be worn or requires adjustment,

2 power cylinder mounting may be loose or incorrectly attached.

Do It Yourself Car Diagnosis

Do It Yourself Car Diagnosis

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