Chevrolet LIGHT DUTY TRUCK (SERIES 10-35) Service Manual page 229

3B3-14 POWER STEERING SYSTEM
POWER STEERING
GAGE J-5176-01
PRESSURE HOSE TO
P /S G E A R
Fig. 3B3-1 2 -C h e ckin g Power Steering Pressures
. Increase engine speed to approximately 1500 rpm.
6
7. Turn the wheels (off ground) right and left, lightly
contacting the wheel stops.
. Add oil if necessary.
8
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 foamy, allow vehicle to stand a
few minutes with engine off and repeat above procedure.
a. Check belt tightness and 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 of the truck, particularly sheet metal except where
design calls for a clamp.
c. Check oil level, filling to proper level if necessary,
following operations 1 through 10. This step and Step "D"
are extremely important as low oil level and/or air in the
oil are the most frequent causes of objectional pump noise.
d. Check the presence of air in the oil. If air is present,
attempt to bleed system as described in operations
10. If it becomes obvious that the pump will not bleed after
a few trials, proceed as outlined under Hydraulic System
Checks.
HYDRAULIC SYSTEM CHECKS
The following procedure outlines methods to identify
and isolate power steering hydraulic circuit difficulties. The
test provides means of determining whether 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 component.
Before performing hydraulic circuit test, carefully
check belt tension, fluid level and condition of driving
pulley.
P ow er Steering System Test
Engine must be at normal operating temperature.
Inflate front tires to correct pressure. All tests are made with
engine idling, check idle adjustment and if necessary adjust
engine idle speed to correct specifications listed in Section
6 C and proceed as follows:
LIG H T T R U CK S ER V ICE MANUAL
ADAPTER
J-22326
PRESSURE HOSE
FROM PUMP
through
1
1 . With engine
NOT
hose from pump and install Tool J-5176 using a spare
pressure hose between gauge and pump. Gauge must be
between shut-off valve and pump (Fig. 3B3-12), Open shut-
off valve.
2. Remove filler cap from pump reservoir and check
fluid level. Fill pump reservoir to full mark on dip stick.
Start engine and, momentarily holding steering wheel
against stop, check connections at Tool J-5176 for leakage.
3. Bleed system as outlined under Maintenance and
Adjustments.
4. Insert thermometer (Tool J-5421) in reservoir filler
opening. Move steering wheel from stop to stop several
times until thermometer indicates that hydraulic fluid in
reservoir has reached temperature of 150° to 170°F.
CAUTION: To prevent scrubbing flat
spots on tires, do not turn steering wheel
more than five times without rolling
vehicle to change tire-to-floor contact
area.
5. Start engine and check fluid level adding any fluid
if required. When engine
temperature, the initial pressure read on the gage (valve
open) should be in the 80-125 PSI range. Should this
pressure be in excess of 200 PSI - check the hoses for
restrictions and the poppet valve for proper assembly.
6 . Close gate valve fully 3 times. Record the highest
pressures attained each time.
CAUTION: Do not leave valve fully closed
for more than 5 seconds as the pump
could be damaged internally.
a. If the pressures recorded are within the listed specs
and the range of readings are within 50 PSI, the pump 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 pump and the gear must
be completely disassembled,
reassembled before further 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 pump checks within specifications, leave the
valve open and turn (or have turned) the steering wheel into
both corners. Record the highest pressures and compare
with the maximum pump pressures and compare with the
maximum pump pressure recorded. If this pressure cannot
be built in either (or one) side of the gear, the gear is leaking
internally and must be disassembled and repaired. See the
current Overhaul Manual.
8 . Shut off engine, remove testing gauge, spare hose,
reconnect pressure hose, check fluid level and/or make
needed repairs.
runnning disconnect pressure
is at normal operating
cleaned, flushed and