Chevrolet 1980 Light Duty Truck Service Manual page 205

CONDITION
Low oil pressure due to steering
pump:
(See pum p pressure test.)
Note: Steering system external leakage
Foaming rmlky power steering
fluid, low level and possible
low pressure.
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 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 Unit Repair Manual.
8. Shut off engine, remove testing gauge, spare hose,
reconnect pressure hose, check fluid level and/or make
needed repairs.
POWER STEERING SYSTEM EXTERNAL
LEAKAGE
General Procedure
1. Wipe suspected area dry.
2. Check for overfilled reservoir.
POSSIBLE CAUSE
Loose belt.
Low oil level.
Air in the oil.
Defective hoses or steering gear.
Flow control valve stuck or inopera­
tive.
Loose screw in end of flow control
valve.
Cracked or broken thrust or pressure
plate.
Pressure plate not Hat against cam
ring.
Extreme wear of cam ring.
Scored pressure plate, thrust plate or
rotor.
Vanes not installed properly.
Vanes sticking in rotor slots.
Air in the fluid, and loss of
fluid due to internal pump
leakage causing overflow.
Fig. 3B3-6--Power Steering System Diagnosis Chart E
POWER STEERING SYSTEM
Adjust tension to specification
Fill reservoir to proper level.
Locate source of leak and correct.
Bleed system.
Correct as necessary.
Remove burrs or dirt or replace.
Tighten.
Replace part.
Replace pressure plate.
Replace parts, flush system
Replace parts. (If rotor, replace with
rotating group kit), flush system
Install properly. Radius edge to outside.
Free-up by removing burrs, varnish or
dirt.
Check for leak and correct. Bleed
system. Extremely cold temperatures
will cause system aeriation should
the oil level be low. If oil level
is correct and pump still foams,
remove pump from vehicle and
separate reservoir from housing.
Check welsh plug and housing for
cracks. If plug is loose or housing
is cracked, replace housing.
3. Check for oil aeration and overflow.
4. Check hose connections - tighten if necessary.
5. Verify exact point of leakage.
Example.Torsion bar, stub shaft and adjuster seals are
close together; exact leakage point could be confused.
Example: The point oil drips from is not necessarily the
leakage point - oil overflowing from reservoir for instance.
6. When service is required:
a. Clean leakage area upon disassembly.
b. Replace leaking seal.
c. Check component sealing surfaces for damage.
d. Reset bolt torque to specifications where required.
Customer Descriptions
Some of the customer complaints associated with the
power steering system may be reported as:
3B3-7
CORRECTION
LIG H T T R U C K SERV ICE M ANUAL