Hyundai 35DS-7 Operation Manual page 164

2 2 . TROUBLESHOOTING
1) SYSTEM
Problem
Large fork lowering speed.
Large spontaneous tilt of
mast.
Slow fork lifting or slow mast
tilting.
Hydraulic system makes
abnormal sounds.
Control valve lever is locked
High oil temperature.
C C ause
Seal inside control valve defective.
Oil leaks from joint or hose.
Seal inside cylinder defective.
Tilting backward : Check valve defec-
tive.
Tilting forward : tilt lock valve defect-
ive.
Oil leaks from joint or hose.
Seal inside cylinder defective.
Lack of hydraulic oil.
Hydraulic oil mixed with air.
Oil leaks from joint or hose.
Excessive restriction of oil flow on
pump suction side.
Relief valve fails to keep specified
pressure.
Poor sealing inside cylinder.
High hydraulic oil viscosity.
Mast fails to move smoothly.
Oil leaks from lift control valve spool.
Oil leaks from tilt control valve spool.
Excessive restriction of oil flow pump
suction side.
Gear or bearing in hydraulic pump
defective.
Foreign matter jammed between sp-
ool and valve body.
Valve body defective.
Lack of hydraulic oil.
High oil viscosity.
Oil filter clogged.
6-20
Remedy
Replace spool or valve body.
Replace.
Replace packing.
Clean or replace.
Clean or replace.
Replace.
Replace seal.
Add oil.
Bleed air.
Replace.
Clean filter.
Adjust relief valve.
Replace packing.
Change to SAE10W, class CD engine
oil.
Adjust roll to rail clearance.
Replace spool or valve body.
Replace spool or valve body.
Clean filter.
Replace gear or bearing.
Clean.
Tighten body mounting bolts uniform-
ly.
Add oil.
Change to SAE10W, class CD engine
oil.
Clean filter.