GMC 4000 Series Service Manual page 511

Sec. 9B
Page 500
POWER STEERING
QUICK REFERENCE TROUBLE SHOOTING CHART
NOTE: Some of the remedial procedures suggested for conditions out­
lined in this chart constitute overhaul of components which is not within the
scope of this manual. Refer to "Overhaul" section of applicable manual for
proper method of accomplishing these corrections.
C O ND ITIO N
1. Pump Noise. Loose belt.
Hoses touching other parts of truck.
Low oil level.
A ir in the oil.
Excessive back pressure caused by hoses or steer­
ing gear.
Scored pressure plate.
Vanes not installed properly.
Extrem e wear of pump ring.
Vanes sticking in rotor slots.
Face of thrust plate scored.
Scored rotor.
Defective flow control plunger.
2. Leaks at top of
Reservoir too full.
ot reservoir.
A ir in the oil.
3. Leaks at the
0 -Ring seal cut.
reservoir.
0 -Ring im properly installed.
Not tightened sufficiently.
4. Leaks at the
pressure fitting
Cross threaded or damaged seat.
or mounting stud.
Defective seat on hose end.
Damaged seals.
5. Leaks at the shaft Defective seal.
seal.
Damaged shaft.
Poor casting.
6. Leaks in metal
parts.
Loose drive belt.
7. Pump inoperative,
poor, or no assist.
Low oil level.
A ir in the oil.
Defective hoses or steering gear as determined
by test outlined under gear section later in this
chart.
Flow control valve stuck.
Loose nut in end of flow control valve.
Pressure plate not flat against ring.
Extrem e w ear of pump ring.
Scored pressure plate, thrust plate, and or rotor.
G M C S E R V I C E M A N U A L
(Type 549-DV and 5 5 3 -DV Power Steering)
HYDRAULIC PUMP
CAUSE REMEDY
Tighten belt.
A djust hose position.
Fill reservoir.
Locate source of air leak and correct.
Locate restriction and correct .B le e d system .
Lap away light scoring. Replace heavily scored part.
Install properly.
Replace ring.
Free up by removing burrs or dirt.
Lap away light scoring. Replace heavily scored part.
Lap away light scoring. Replace heavily scored part.
Replace assem bly.
Fill to proper level.
Locate source of air leak and correct.
Replace 0-Ring seal.
Install seal properly.
Torque to 30-40 ft.-lbs.
Replace damaged part.
Replace hose.
Replace seals.
Replace seal.
Replace shaft.
Replace defective parts.
.Tighten belt.
Fill reservoir to proper level.
Locate source of air leak and correct.
Correct.
Remove burrs or dirt.
Tighten nut.
Correct condition.
Replace pump ring.
Lap away light scoring. Replace heavily scored parts.