TCM FD35C9 - 4.8 Main Pump Troubleshooting; 4.9 Control Valve Troubleshooting; 4.10 Lift Cylinder Troubleshooting

4-5
4.8 MAIN PUMP
Problem Probable cause Remedy
1. Insufcient oil discharge
from pump
Low oil level in tank Add oil.
Air mixed in suction line Retighten pipe connections.
Clogged suction line or strainer
Clean hydraulic line and
change oil.
Bushing, gear or pump body damaged due to
foreign matter
Clean hydraulic line and
replace pump assembly.
2. Noisy pump
Cavitation due to clogged strainer
Clean strainer or replace lter
element.
Bushing and gear worn or seized Replace bushing and gear.
Pump body worn or seized Replace pump assembly.
Improper centering of pump Adjust.
3. Oil leakage from pump
“O”-ring or oil seal damaged Replace.
End cover loose
Check bolts and retighten
evenly.
4.9 CONTROL VALVE
Problem Probable cause Remedy
1. Plunger fails to operate
normally
Foreign matter in valve
Clean hydraulic line and
change oil.
Lever or linkage bent Repair.
Plunger bent Replace valve assembly.
Return spring damaged Replace.
2. Oil leakage from oil seal
Seal contaminated with paint
Replace seal and clean control
valve.
Foreign matter caught in seal
Replace seal and clean control
valve.
Plunger damaged
Replace valve assembly or
plunger section.
Seal plate loose Clean and retighten.
Seal damaged Replace seal.
3. No pressure builds up
Relief valve defective Replace relief valve assembly.
Relief valve pressure setting improper
Adjust relief valve pressure
setting.
4.10 LIFT CYLINDER
Problem Probable cause Remedy
1. Oil leakage
Cap “O”-ring damaged Replace.
Cap oil seal defective Replace.
Piston rod damaged or bent Repair or replace.
2. Cylinder jolts
Piston rod bent Repair or replace.
Low hydraulic oil level Add oil to specied level.
Defective pump See “4.8 MAIN PUMP.”
3. Natural drop of piston
Piston packing damaged or worn Replace.
Cylinder inner surface damaged or worn Repair or replace.
Control valve defective See “4.9 CONTROL VALVE.”