Lesson 2/Learning Event 2
Start the engine, and check the hydraulic system for leaks while oil
pressure is applied. Remember that high pressure is developed in the system
only when a turning effort is applied on the steering wheel. So, have a
buddy turn the steering wheel while you look for slight oil leaks. Don't
hold the steering against the steering stop for more than a few seconds at a
time because this can damage the hydraulic system. The relief valve will
open to prevent the pressure from going high enough to rupture lines and
units; however, the high pressure creates heat which can damage the system.
Roadtest the vehicle. Check for any tendency to wander, weave back and
forth, or shimmy. Check for excessive free play, binding, and for pulling
to the right or left. Check the action of the steering assist through both
right and left turns. The steering effort required should be so small that
you can turn the steering wheel with your thumb and forefinger while the
vehicle is moving.
ISOLATING FAULTS
If the road test reveals any steering faults, the next step is to find the
cause. (Faults that are peculiar to the power steering system of the 5ton
truck will be described.)
If the steering was hard or was binding on turns, the trouble could be the
power steering gear, steering column jacket linkage, or steering knuckle
pivots. To pinpoint the trouble, you will need to disconnect the steering
linkage from the steering gear at the point where the upper drag link
connects to the pitman arm.
To disconnect the drag link from the pitman arm, remove the cotter
pin and dust shield from the upper drag link end. Unscrew the drag
link adjusting plug as far as possible without removing it. Turn
the steering wheel back and forth to loosen the ball seats on the
pitman arm ball stud. Then, lift the drag link from the pitman arm
ball stud.
Use a jack and raise the front axle until both front wheels are off
the ground. Grasp one front wheel at the front and rear, and pivot
the wheels back and forth on their steering knuckles. If the wheels
pivot easily, the binding is not caused by the steering knuckles or
steering linkage.
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