Have shut-off valve open.
To test the pressure in both hoses connecting the valve to the cylinder, apply steering effort at the steering wheel.
With engine running at recommended idle speed, watch pressure as someone tries to steer in both directions while
Remember not to hold at maximum relief pressure very long. The pump can be damaged by overheating.
If maximum pressure is not attained, this condition indicates there is internal valve leakage past the restricting control
edges of the valve spool or severe external leakage past the seals. The valve should be disassembled and inspected.
When a valve has been scored or seized it should be replaced. Polishing of much extent will destroy the very close fit
necessary between the spool and the body. A valve spool must move freely and without sticking to operate properly. Dirt,
burrs, etc., cannot be tolerated in a valve.
If the valve tests okay, there may be internal leakage or bind in the power cylinder or binding in the steering system, or
insufficient oil flow.
The cylinder should be disassembled and inspected. Look for scored wall, broken piston ring, bent or scored piston rod
and binding by the linkage.
Insufficient Oil Flow.
In most systems a flow in excess of just maintaining pressure is needed for desired speed of steering. If it is possible to
steer slowly with enough hydraulic power to steer with ease, but a lack of power and hard steering is experienced when
trying to steer faster, the problem may be one of insufficient oil flow.
Common Causes are:
1. Fitting leaks-at seats, threads, seals.
2. Hose leaks-worn or burst, bad joints, pin holes.
3. O-ring seals-worn, cut damaged, split, flats, taken set, dirt under seal, cooked by excessive oil temperature. (O-rings
should be soft and pliable).
4. Reservoir spilling--may be too full, filter out of place, filter charred, oil may be overheated.
Check filter. Swinging dipstick may have rubbed opening in the filter elements which allows unbaffled stream of oil to
shoot directly at the filler cap and out the breather. A swinging dipstick may loosen the rivet which holds the vent baffle
and dipstick in the cap. In time, the rivet, baffle and dipstick may fall into the reservoir leaving a hole in the cap out of
which oil can readily spill. As oil is sprayed out of the reservoir, the level drops sufficiently to allow the outlet to pump to be
only partially covered as the oil slushes around. This produces aeration and frothing which forces more oil out of the cap.
The filter must be replaced as frequently as necessary to be sure it is doing its function as a filter of the oil.