GMC 4000 Series Service Manual page 514

CONTROL VALVE AND POWER STEERING GEAR (Cont.)
CONDITIO N
Hard steering when
parking. (Cont'd)
Low oil pressure due to restriction in hoses:
a. Check for kinks in hoses.
b. Foreign object stuck in hose.
Low oil pressure due to steering gear
a. Leakage at valve rings, valve body to worm
seal.
b. Loose fit of spool in valve body or leaky valve
body.
13. Excessive effort Broken torsion bar
required to turn.
Momentary increased effort when turning wheel. Replace cylinder assem bly.
1. Internal leaks.
Around piston rod seals.
2. External leaks.
At hose connections.
Around welded joints.
End play present.
3. Excessive ball
Worn ball seats.
socket movement.
Loose bolts.
4. Piston rod end
clamp movement.
G M C S E R V I C E M A N U A L
CAUSE
Comparing the m aximum pressures obtained in these two tests
will indicate source of trouble as fo llo w s:
(a ) First test pressure low and second test pressure normal —
(b ) First test and second test pressures equally lo w - in d ic a te s
If the above test shows trouble to be in pump, see hydraulic
pump procedures described previously.
If trouble is shown to be in steering gear or hoses, exam ine for
external oil leaks as described under L E A K S — ITEM 5.
Remove kinks.
Remove hoses and remove restricting object or replace hose.
Remove gear from truck for disassem bly and replace seals.
Replace valve.
Replace torsion bar and stub shaft assem bly.
POWER CYLINDER
1.
2. Cylinder relief valve not w o rk in g -re p la c e cylinder assem bly.
Tighten or replace cylin der if tightening does not remedy condition.
Replace cylinder assem bly.
Adjust to specifications.
Replace seats.
Torque to specifications after proper positioning to specifications.
POWER STEERING
REMEDY
indicates faulty external oil lines, or steering gear.
faulty oil pump.
Replace seals.
Sec. 9B
Page 503