9-9
6. HYDRAULIC SYSTEM
Trouble symptom
1. Large fork lowering speed.
2. Large spontaneous tilt of
mast.
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Seal inside control valve defective.
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Oil leaks from joint or hose.
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Seal inside cylinder defective.
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Tilting backward : Check valve defec-
tive.
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Tilting forward : Tilt lock valve defect-
ive.
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Oil leaks from joint or hose.
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Seal inside cylinder defective.
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Clean or replace.
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Clean or replace.
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Replace.
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Replace seal.
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Replace spool or valve body.
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Replace.
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Replace packing.
Probable cause
Remedy
3. Slow fork lifting or slow
mast tilting.
4. Hydraulic system makes
abnormal sounds.
5. Control valve lever is locked
6. High oil temperature.
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Lack of hydruilc oil.
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Hydrauic oil mixed with air.
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Oil leaks from joint or hose.
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Excessive restriction of oil flow on
pump suction side.
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Relief valve fails to keep specified
pressure.
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Poor sealing inside cylinder.
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High hydraulic oil viscosity.
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Mast fails to move smoothly.
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Oil leaks from lift control valve spool.
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Oil leaks from tilt control valve spool.
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Excessive restriction of oil flow pump
suction side.
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Gear or bearing in hydraulic pump
defective.
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Foreign matter jammed between sp-
ool and valve body.
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Valve body defective.
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Lack of hydraulic oil.
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High hydraulic oil viscosity.
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Oil filter clogged.
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Add oil.
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Bleed air.
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Replace.
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Clean filter.
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Adjust relief valve.
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Replace packing.
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Change to SAE10W, class CF engine
oil.
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Adjust roll to rail clearance.
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Replace spool or valve body.
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Replace spool or valve body.
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Clean filter.
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Replace gear or bearing.
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Clean.
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Tighten body mounting bolts uniform-
ly.
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Add oil.
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Change to SAE10W, class CF engine
oil.
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Clean filter.