Chevrolet 1977 light duty truck, Service Manual

Page: 232 / 861

5. Raise fro n t end o f vehicle so that wheels are off
the ground.
6. Increase engine speed to approxim ately 1500
rpm.
7. T u rn the wheels (off ground) right and left,
lightly contacting the wheel stops.
8. A dd oil if necessary.
9. Lower the vehicle and turn wheels right and left
on the ground.
10. Check oil level and refill as required.
11. If oil is extremely foam y, allow vehicle to stand
a few minutes with engine off and repeat above
procedure.
a. Check belt tightness an d check for a bent or
loose pulley. (Pulley should not wobble with engine
running.)
b. Check to make sure hoses are not touching
any other parts o f the truck, particularly sheet metal
except w here design calls for a clamp.
c. Check oil level, filling to pro p er level if
necessary, following operations 1 through 10. This step
an d Step " D " are extremely im p o rta n t as low oil level
a n d / o r air in the oil are the most frequent causes of
objectional p u m p noise.
d. Check the presence o f air in the oil. If air is
present, attem pt to bleed system as described in
operations 1 through 10. If it becomes obvious that the
p u m p will not bleed a fte r a few trials, proceed as
outlined u n d e r Hydraulic System Checks.
Hydraulic System Checks
T h e follow ing p ro c e d u re outlines m eth o d s to
identify and isolate power steering hydraulic circuit
difficulties. The test provides means o f determ ining
w h e th e r power steering system hydraulic parts are
actually faulty. This test will result in readings indicating
faulty hydraulic operation, and will help to identify the
faulty com ponent.
Before p e rfo rm in g hydraulic circuit test, carefully
check belt tension, fluid level and condition o f driving
pulley.
Pow er S teering Hydraulic System Test
Engine must be at n o rm al operating tem perature.
Inflate fro n t tires to correct pressure. All tests are m ade
with engine idling, check idle adjustm ent and if
necessary adjust engine idle speed to correct specifica­
tions listed in Section 6C and proceed as follows:
1. W ith engine NOT r u n n n in g disconnect pressure
hose from pu m p and install Tool J-5176 using a spare
pressure hose between gauge and pum p. G au g e must be
between shut-off valve and p u m p (Fig. 3B-43), Open
shut-off valve.
2. Remove filler cap from pu m p reservoir and
check fluid level. Fill pu m p reservoir to full mark on dip
stick. Start engine and, m om entarily holding steering
wheel ag ain st stop, check connections at Tool J-5176 for
leakage.
Fig. 3B 43 Checking Power Steering Pressures
3. Bleed system as outlined und er M aintenance
and Adjustments.
4. Insert th erm o m 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 o f 150 to
170 F.
CAUTION: To prevent scrubbing fla t spots on
tires, do not turn steering wheel more than Jive
times without rolling vehicle to change tire-to-
floor contact area.
5. Start engine and check fluid level add in g any
fluid if required. W hen engine is at norm al operating
tem perature, the initial pressure read on the gage (valve
open) should be in the 80-125 PSI range. Should this
pressure be in excess o f 200 PSI - check the hoses for
restrictions and the poppet valve for p roper assembly.
6. Close gate valve fully 3 times. Record the
highest pressures attained each time.
CAUTION: Do not leave valve fu lly closed fo r
more than 5 seconds as the p u m p could be
dam aged internally.
a. If the pressures recorded are within the listed
specs and the range o f readings are within 50 PSI, the
p u m p is functioning within specs. (Ex. Spec. 1250 - 1350
PSI - readings - 1270 - 1275 - 1280).
b. If the pressures recorded are high, but do not
repeat within 50 PSI, the flow controlling valve is
sticking. Remove the valve, clean it and remove any
burrs using crocus cloth or fine hone. If the system
contains some dirt, flush it. If it is exceptionally dirty,
both the pu m p and the gear must be completely
disassembled, cleaned, flushed and reassembled before
fu rth er usage.
c. If the pressures recorded are constant, but
more than 100 PSI, below the low listed spec., replace the
flow control valve and recheck. If the pressures are still
low. replace the rotating group in the pump.
7. If the p u m p checks within specifications, leave
A
HIGH PRESSURE HOSE FROM PUMP
B
ADDITIONAL HIGH PRESSURE P/S
HOSE TO GEAR
C
TOOL J-5176