GMC 1986 P-Truck Service Manual page 213

DIAGNOSIS OF POWER STEERING SYSTEM (CONT.)
PRO BLEM '"
Hard Steering Effort 5. Low fluid level in reservoir.
In Both Directions
(Continued) 6. High internal leakage (steering gear or
7. Sticky flow control valve.
8. Lower coupling flange rubbing against
9. Steering gear adjusted too tight.
10. Improper front end alignment.
F oam ing M ilky P ow er
Steering Fluid, Low
Level And Possible
Low Pressure
Low Oil Pressure
1. Check for kinks in the hose.
Due To Restriction
In The Hose 2. Foreign object stuck in the hose.
Low Oil Pressure 1. Pressure loss in cylinder due to worn
Due To Steering
Gear. Refer To
" Power Steering
System Test" In
2. Leakage at the valve rings and valve
This Section.
3. Leakage at the valve body or a loose
4. Damaged poppet valve.
Low Oil Pressure
1. Flow control valve stuck or inoperative.
Due To Steering 2. Pressure plate not flat against the cam
Pump. Refer To
" Power Steering
3. Extreme wear of cam ring.
System Test" In 4. Scored pressure plate, thrust plate or
This Section.
5. Vanes sticking in rotor slots.
6. Vanes not installed properly.
7. Air in oil.
8. Low oil level.
9. Loose belt.
10. Damaged hoses or steering gear.
POSSIBLE CAUSE
pump).
steering gear adjuster plug.
Air in the fluid, and loss of fluid due
to internal pump leakage causing over­
flow.
piston ring or scored housing bore.
body to the worm seal.
fitting spool.
ring.
rotor.
POWER STEERING 3B3-7
CORRECTION
5. Fill to proper level. Inspect lines and
joints for external leakage.
6. Refer to " Power Steering System
Test" in this section.
7. Replace or clean the valve.
8. Loosen the pinch bolt and assemble
properly.
9. Adjust over-center and thrust bearing
preload to specifications.
10. Check and adjust to specifications.
Check for leak and correct. Bleed
system. Extremely cold temperatures
will cause system aeriation should
the oil level be low. If oil level is cor­
rect and pump still foams, remove
pump from vehicle and separate res­
ervoir from housing. Check welsh
plug and housing for cracks. If plug is
loose or housing is cracked, replace
housing.
1. Remove the kinks or replace the
hose.
2. Remove the foreign object or replace
the hose.
1. Disassemble the steering gear as
outlined in the unit repair manual. In­
spect the ring and housing bore. Re­
place the affected parts.
2. Disassemble steering gear and re­
place seals.
3. Replace the valve.
4. Replace the poppet valve.
1. Replace or clean the valve.
2. Replace the pressure plate.
3. Replace and flush the system.
4. Replace parts. (If rotor, replace with
rotating group), flush the system.
5. Free-up by removing burrs, varnish or
dirt.
6. Install properly. Radius edge to the
outside.
7. Locate source of leak and correct.
Bleed the system.
8. Add power steering fluid as required.
9. Adjust tension to specifications.
10. Replace as necessary.