Chevrolet 1977 light duty truck Service Manual page 216

adjustm ent or disassembly o f the power steering gear or
p u m p is attem pted.
System Checks
M any factors affect power operation o f the steering
system, o f which the most com m on are:
1. Fluid level and condition.
2. Drive belt tension.
3. Loose c om ponent mountings.
4. Loose p u m p pulley.
These factors must be checked and corrected before
m aking any further diagnosis o f the steering system. The
need for proper diagnosis cannot be over-emphasized.
A fter the source o f the problem has been found,
determ ine the cause. For example, if the oil level in the
reservoir is found to be low, refill and check the entire
hydraulic system for oil leaks. Refilling the reservoir will
not necessarily correct problem.
Fluid Level
1. R un engine to norm al operating temperature,
then shut engine off. Remove reservoir filler cap and
check oil level to " h o t" m ark on dipstick.
2. If oil level is low, add hydraulic fluid to proper
level on dipstick and replace filler cap.
N OTE: W hen a dd in g or making a complete fluid
change, always use G M power steering fluid or
equivalent.
3. W hen checking fluid level after the steering
system has been serviced, air must be bled from the
system. Proceed as follows:
a. W ith wheels turned all the w ay to the left,
add power steering fluid to "C o ld " mark on dipstick.
b. Start engine, and run ning at fast idle, recheck
fluid level. Add fluid if necessary to "C old" m ark on
dipstick.
c. Bleed system by turning wheels from side to
side without hitting stops. M aintain fluid level just above
internal p u m p casting. Fluid with air in it will have a
light tan or red appearance. This air must be eliminated
from fluid before norm al
obtained.
d. Return wheels to center position and continue
to run engine for two or three minutes, then shut engine
off.
e. Road test car to m ake sure steering functions
normally and is free from noise.
f. Recheck fluid level as described in steps 1 and
2, m aking sure fluid level is at " h o t" m ark on dipstick
after the system has stabilized at its normal operating
tem perature approximately 170° to 190°F.
B elt Adjustm ent
W hen adjusting a power steering p u m p belt, never
pry against the pu m p reservoir or pull against the filler
neck. To increase belt tension move the pu m p outward
by prying against the p u m p housing casting extension
directly behind the pum p drive pulley.
A belt that has been
considered to be a used belt and should be tightened to
steering action can be
previously tensioned is
75 pounds. A belt that has never been tensioned is
considered to be a new belt and should be tightened to
125 pounds.
Place belt tension gage, J-23600 or equivalent
midway between the pulleys on drive belt being checked.
If the belt tension is incorrect proceed as follows:
1. W hen power steering pum p is driven by a single
belt:
a. Loosen the p u m p attaching bolts and adjust
the belt to correct tension by moving the pu m p outward,
away from the engine.
b. Snug all pu m p mounting bolts and remove
pry bar.
c. Tighten all pum p mounting bolts to specified
torque.
d. Check belt tension
tension gage.
Hydraulic System Checks
The following p rocedure
identify and isolate power steering hydraulic circuit
difficulties. The test provides means o f determ ining
whether power steering system
actually faulty. This test will result in readings indicating
faulty hydraulic operation, and will help to identify the
faulty component.
Before perform ing hydraulic circuit test, carefully
check belt tension, fluid level and condition o f driving
pulley.
Power Steering Hydraulic System Test
Engine must be at normal operating temperature.
Inflate front tires to correct pressure. All tests are made
with engine idling, check
necessary adjust engine idle speed to correct specifica­
tions listed in Section 6C and proceed as follows:
1. With engine N O T running disconnect pressure
hose from pum p and install Tool J-5176 using a spare
pressure hose between gauge and pump. G au ge must be
between shut-off valve and pump. Open shut-off valve.
2. Remove filler cap from pum p reservoir and
check fluid level. Fill p u m p reservoir to full mark on
dipstick. Start engine and, m omentarily holding steering
wheel against stop, check connections at Tool J-5176 for
leakage.
3. Bleed system as outlined under M aintenance
and Adjustments.
4. Insert therm om eter (Tool J-5421) in reservoir
filler opening. Move steering wheel from stop to stop
several times until therm om eter indicates that hydraulic
fluid in reservoir has reached tem perature of 150° to
170°F.
CAUTION: To prevent scrubbing fla t spots on
tires, do not turn steering wheel more than fiv e
times without rolling vehicle to change tire-to-
floor contact area.
5. Start engine and check fluid level adding any
fluid if required. W hen engine is at norm al operating
temperature, the initial pressure read on the gauge (valve
open) should be in the 80-125 PSI range. Should this
and remove the belt
outlines m ethods to
hydraulic parts are
idle adjustment and if