Valves; Bypass Valve; Relief Valve Troubleshooting; Spool Valve Troubleshooting - Toro Dingo TX 413 Service Manual

Valves

Valves are used to provide control of pressure,
direction and volume in a hydraulic system.

Bypass Valve

Bypass valves are a type of flow control valve used
to manually open a hydraulic circuit allowing oil to
bypass from one side of a circuit to the other. Bypass
valves allow units to be moved without starting the
engine.

Relief Valve Troubleshooting

Relief valves are a type of pressure control valve.
Relief valves are used both to regulate system pres-
sure and to protect hydraulic circuits from pressures
which are higher than its design.
Erratic/Low Pressure
• Incorrect pressure setting
• Valve held open by dirt/debris
• Poppet and or seat worn or damaged
• Weak or damaged spring
• Blocked orifice
No Pressure
• Blocked orifice
• Poppet not properly seating
• Weak or damaged spring
• Valve held open by dirt/debris
• Poppet and or seat worn or damaged
• Cracked housing
System pressure can not be adjusted or is excessive
• Broken or worn spring
• Incorrect spring
• Restricted drain line
Excessive Heat
• Continuous operation at relief pressure
• Oil viscosity too high
• Valve seat leakage
• Restriction hydraulic line
TX 413 Service Manual
HYDRAULIC TROUBLESHOOTING

Spool Valve Troubleshooting

Spool valves are a type of directional control valve
that allows oil flow to be diverted to a remote circuit
when the spool is not centered.
Difficult Spool Shifting
• Control lever binding
• Lack of pressure
• Bad centering spring
• Spool out of adjustment
• Contamination
Cylinder Creep
• Spool not properly centered
• Spool worn or damaged
• Cylinder wear
• Cylinder seals

Control Valve Leaks

Worn/Damaged O-Rings
• Replace affected O-rings
• If damaged from contamination, locate the source
Valve Parts Broken/ Damaged
• Inspect to determine cause
• If cracked, check system pressure
• Confirm hydraulic lines are attached correctly
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