STEERING CONTROL VALVE WITH
RELIEF VALVE OPEN
4. Flow control valve. 5. Pilot valve. 7. Orifice.
When the pilot valve opens, oil flows through orifice
(7) and past the pilot valve. The flow of oil past the
orifice causes a lower pressure in the chamber for the
flow control springs. This lets the pressure of the oil in
the inlet passage move flow control valve (4). Oil from
inlet (2) can flow through the holes in the flow control
valve. This releases the extra pressure from the circuit.
When the outside force is gone and the pressure is
reduced, the flow control valve and pilot valve return to
their normal positions.
Left Turn Position
The control valve operation for a LEFT TURN is similar
to that for a RIGHT TURN. When the steering wheel is
turned to the left, the valve spool moves into the valve
body. Pump oil, from the inlet, flows through the slots
on the valve spool into outlet (1 I). This oil then flows to
the cylinders and a LEFTTURN is the result.
The cylinder pressure is felt through passage (12), and
against the pilot valve and flow control valve. The rest of
the relief valve operation is the same as a RIGHT TURN.
The 5P5224 Pressure Gauge Kit can be used to
make the pressure tests of the steering system. Before
any tests are made, visually inspect the complete
hydraulic stem for leakage of oil and for parts that have
damage. For some of the tests a magnet and a
measuring rule (either for inches or millimeters) are
WARNING: When testing and adjusting the
steering system, move the machine to a smooth
horizontal location. Move away from personnel and
machines that are at work. There must be only one
operator. Keep all other personnel away from the
A visual inspection of the steering system and its
components is the first step when a diagnosis of a
problem is made. To remove the tank filler cap, slowly
turn the filler cap until it is loose. If oil comes out the
bleed hole, let the tank pressure lower before the filler
cap is removed. Make the following inspections:
1. Measure the oil level.
2. Check for air in the hydraulic oil. Do this
immediately after the machine has been operated (%
with the engine still running). Use a clear bottle or
container to get a sample of the oil in the hydraulic tank.
Check the sample to see if there are air bubbles in the
3. Remove the filter elements and look for particles.
removed from the oil by the filter element. A
magnet will separate ferrous particles from non-ferrous
particles (Piston rings, O-ring seals, etc.).
4. Check all oil lines and connections for damage or
Performance tests of the steering system can be used
for a diagnosis of poor performance and to find the
source of oil leakage inside the hydraulic system. The oil
must be at the normal temperature for operation when
the tests are done.
RECOMMENDED CORRECTIVE ACTION
Steering wheel hard to turn.
1. Mechanical linkage does not move freely.
2. Valve spool does not move freely in its bore.
a. Check mechanical linkage, repair or replace
b. Check valve spool, repair or replace as