Chevrolet 70 1969 Series, Shop Manual

Page: 469 / 913

STEERING SYSTEM 9B-18
ventional cab models or to the transmission con­
trol island panel front support on tilt cab models.
When the slightest evidence of dirt, sludge,
or water is discovered in the system, drain and
refill with clean hydraulic fluid recommended in
L U B R IC A T ION (SEC. 0). To drain system, discon­
nect fluid lines at power cylinder. Air in the fluid
system will cause spongy action and noisy oper­
ation. When any hose has been disconnected or
when fluid has been lost for any reason, the sys­
tem must be bled after adding fluid. Bleed system
as directed later in this section under "Bleeding
Hydraulic System."
Should the power steering system become in­
operative due to loss of hydraulic fluid, pump pres­
sure line should be re-routed from pump outlet
directly back to pump reservoir.
IM P O R T A N T : Do not operate pump without
fluid in pump reservoir.
The hydraulic pump, control valve, and power
cylinder do not require adjustment on the vehicle.
The only adjustments are on the steering linkage.
Adjustment of these parts are normally required
only when the units have been removed or dis­
connected.
N O T E : These adjustments, with the exception
of the power cylinder piston rod end, are the same
as previously described in "M E C H A N IC A L S T E E R ­
IN G " of this group.
Wheel alignment must be maintained to proper
specifications. Refer to "F R O N T E N D A L IG N -
M E N T " ( S E C . 3A) of this manual for proper pro­
cedures for checking front end alignment. Im ­
proper tire inflation will also affect operation of
the power steering. The tires, therefore, should
be checked at regular intervals.
Because of the power assist from the power
steering system it is more difficult to detect de­
fects in the steering system. Therefore, periodic
maintenance is very important on a vehicle having
power steering.
BLEEDING HYDRAULIC SYSTEM
When a power steering pump or power cylin­
der has been installed or a disconnected oil line
has been reconnected, the air that has entered the
system must be bled out before the vehicle is again
operated. If air is allowed to remain in the hy­
draulic fluid system, noisy and unsatisfactory
operation of the steering system will result. Bleed
air from the hydraulic system as follows:
N O T E : When hydraulic fluid is added to power
steering system, fluid should be poured through a
Figure 2— Power Steering System (Series TM/W M80) (Typical)
200 mesh wire screen. Use only the hydraulic fluid
recommended in LU BR IC ATION (SEC. 0).
1. Fill pump fluid reservoir to proper level
and let fluid remain undisturbed for about two
minutes.
2. Raise front end of the vehicle so that front
wheels are off the ground.
3. Turn wheels to right and left to wheel
"stops" to eliminate air pockets in the power cyl­
inder. Continue this operation until fluid in reser­
voir stops bubbling. Maintain fluid level during
this operation.
4. Start the engine and run at idle for two
Figure 3— Checking Pump Hydraulic Pressure
(Vane Type Pump) (Typical)
CHEVROLET SERIES 70 -80 H EAVY DUTY TRUCK S H O P M A N U A L