Page Issue 01Chapter - Fault Diagnosis14:2
VT551 - Maintenance
HYDRAULIC SYSTEMS
FAULT SYMPTOM POSSIBLE CAUSE
Hydraulic oil frothing 1. Air getting into system. Check LP pipe to pump,
jubilee clips for tightness.
2. Defective pump shaft seal.
3. Return pipe separated from underside of return
filter inside hydraulic tank.
Sluggish hydraulics 1. Cartridge valve not travelling full extent -
measure oil flow.
2. Blocked filters.
3. Air in oil.
4. Pump output incorrect - measure oil flow.
Fan Speed Too Low 1. Excessive leak off from motor - measure oil flow.
2. Relief valve pressure too low - reset.
PNEUMATIC SYSTEMS
FAULT SYMPTOM POSSIBLE CAUSE
Low pressure warning 1. Air pressure switch faulty.
buzzer on continuously 2. Insufficient pressure in Johnston system.
Constant air leak from 1. Cylinder seals leaking internally.
solenoid block 2. Air solenoid faulty.
WATER SYSTEMS
FAULT SYMPTOM POSSIBLE CAUSE
Jet continuously leaking 1. Grit under armature seating.
2. Armature stuck open.
3. Manual override on.
No water to wash down 1. Water pump filter blocked.
hose or jets 2. Water tank filter blocked.
3. Filter isolation valve closed.
4. Filter assembled incorrectly.
5. Pump valves fitted incorrectly after overhaul.
Lack of pressure 1. Grit under relief valve seating.
2. Relief valve spring broken.
3. Relief valve stuck open.
4. Relief valve worn.
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