Group 25, Steering Column and Gear
SM 765, Dec ’06 Stering System Relief Pressure Check and Adjustment • 25-4-1
CAUTION
!
SAFE PARKING. Before working on truck:
1. Park truck on a hard, level, and solid
surface, such as a concrete floor with no
gaps or breaks.
2. Put upright in vertical position and fully
lower the forks or attachment.
3. Put all controls in neutral. Turn key
switch OFF and remove key.
4. Apply the parking brake and block the
wheels.
Description and Operation
Steering system relief pressure settings above the speci-
fied values can cause failure of the hydraulic lines, dam-
age to seals in the steering gear, and ball joint breakage on
the steer axle.
The steering system’s pressure relief valve is part of the
main hydraulic pump assembly. Steering system relief
pressure is adjustable and should be checked if indicated
by troubleshooting. Use the gauge port on the pump to
check steering relief pressure.
Steering system relief pressure setting should be 10000
kPa (1450 psi).
N
TE
If relief pressure is not correct, the problem
may be caused by dirt in the valve or worn
parts, including steering control valve and
main hydraulic pump. Generally, if the relief
pressure measured when the steering system
is in bypass is not correct, the priority
demand valve should be replaced.
WARNING
!
Do not use your hands to check for hydraulic
leakage. Use a piece of cardboard or paper to
search for leaks. Escaping fluid under pres-
sure can penetrate the skin causing serious
injury. Relieve pressure before disconnecting
hydraulic or other lines. Tighten all connec-
tions before applying pressure. Keep hands
and body away from pinholes and nozzles
which eject fluids under high pressure.
If any fluid is injected into the skin, it must
be surgically removed within a few hours by
a doctor familiar with this type of injury or
gangrene may result.
Steering System Relief Pressure Setting
Check and Adjustment
This procedure requires installation of a pressure gauge at
the gauge port on the main hydraulic pump. The pressure
is measured while the steering handwheel is turned fully
in one direction to put the steering system in bypass.
Steering system relief pressure setting may be checked
using a Mico Quadrigage (Clark Part No. 1800106) or
with a conventional pressure gauge, 0-20,700 kPa (0-3000
psi).
1. Tilt the steering column fully forward and raise the
seat deck.
Section 4
Stering System Relief Pressure Check and Adjustment
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