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TROUBLESHOOTING THE Bocat X337 X341 HYDRAULIC CIRCUIT



No hydraulic operation at one or more
circuits.
Hydraulic power insufficient to one or
more circuits.
All hydraulic speed too slow.
Oil temperature too high.
Pump (Piston) response slow
Hydraulic oil level low.
Hydraulic pump drive coupling
damaged.
Isolator spool not shifting
Hydraulic pump defective.
Main relief valve defective.
Main relief valve pressure setting
incorrect.
Hydraulic oil level or viscosity
incorrect.
Pump margin too low.
Engine RPM reduced.
Torque limiter set too low/high.
Control valve linkage defective.
Hydraulic pump volume low.
Oil cooler or radiator fins plugged.
Hydraulic oil level low.
Non recommended hydraulic oil.
Relief valve excessively activated.
One or more relief valves not set
correctly.
Extreme operating conditions. High
ambient temperature. (IE: Enclosed
structure).
Fan belt loose.
Piston pump margin too high.
Plugged on stroke orifice.
PROBLEM CORRECTIONCAUSE
TROUBLESHOOTING THE HYDRAULIC CIRCUIT
Refill with correct oil.
Replace.
Repair or replace.
Repair or replace.
Readjust or replace.
Readjust or replace.
Fill to correct level. Use correct
viscosity oil.
Readjust or replace.
Test and adjust.
Check, repair or replace.
Check repair or replace.
Clean oil cooler external surface.
Fill to correct level.
Replace.
Use proper operating procedures.
Readjust or replace.
Tighten fan belt.
Repair or replace.
HYDRAULIC SYSTEM TROUBLESHOOTING
337 (S/N 515411001 & Above) Excavator
–2–5– Service Manual
Control console raised.
Loose fittings or broken hoses.
Low PSI at joystick.
Lever linkage incorrectly adjusted.
Control console lockout switch.
Cylinder internal leakage excessive.
Joystick manifold pressure reducing
valve defective.
Joystick internal leakage excessive.
Isolator spool not shifting.
Pump margin spool not shifting.
Pump compensator spool not shifting.
Lever linkage incorrectly adjusted.
Main relief valve pressure too low.
Lever linkage incorrectly adjusted.
Pump compensator too low.
Pump torque limiter too low.
Cylinder internal leakage excessive.
Joystick manifold solenoid valve
defective.
Joystick manifold pressure reducing
valve defective.
Control valve internal leakage
excessive.
Low tie rod torque on 3 spool & 6 spool
control valves.
Joystick internal leakage excessive.
Low or dirty fluid.
Main relief valve malfunctioning.
Pump margin too low.
Pump torque limiter too low.
Cylinder inoperable.
Cylinder force insufficient.
Cylinder speed too slow.
PROBLEM CORRECTIONCAUSE
TROUBLESHOOTING THE CYLINDER CIRCUIT
Lower control console.
Repair or replace.
Check, repair or replace pressure
reducing valve and or safety valve in
pressure reducing valve body.
Readjust.
Readjust or replace.
Repair or replace.
Repair or replace.
Repair or replace.
Repair or replace.
Repair or replace.
Repair or replace.
Readjust.
Readjust or replace.
Readjust.
Readjust or replace.
Readjust or replace.
Repair or replace.
Repair or replace.
Repair or replace.
Repair or replace.
Tighten tie rods to correct torque.
Repair or replace.
Add or replace the hydraulic fluid.
Readjust or replace.
Repair or replace.
Readjust or replace.
HYDRAULIC SYSTEM TROUBLESHOOTING (Cont’d)
–2–6–
337 (S/N 515411001 & Above) Excavator
Service Manual
Lower control console.
Control console lockout switch
incorrectly adjusted or defective.
Swing lock pin engaged.
Joystick manifold pressure reducing
valve defective.
Swing motor gear defective.
Joystick internal leakage excessive.
Swing motor defective.
Main relief valve set too low..
Swing motor relief valve pressure too
low.
Sequence valve not shifting.
Pump flow low.
Blocked or restricted line to swing
motor.
Joystick internal leakage excessive.
Control valve internal leakage
excessive.
Swing motor internal leakage
excessive.
Control valve spool sticking.
Joystick spool sticking.
Swing motor relief valve set too low.
Swing motor internal leakage
excessive.
Return line filter plugged.
Sequence valve shifting too early.
Swing not operating.
Swing force.
Swing speed too slow.
Swing over run excessive.
Swing motor seal leakage.
Swing stop/start too harsh
PROBLEM CORRECTIONCAUSE
TROUBLESHOOTING THE SWING (SLEW) CIRCUIT
Lower control console.
Readjust or replace.
Disengage lock pin.
Repair or replace.
Repair or replace.
Repair or replace.
Repair or replace.
Readjust or replace.
Readjust or replace.
Repair or replace.
Check, repair or replace.
Replace.
Repair or replace.
Repair or replace.
Repair or replace.
Repair or replace.
Repair or replace.
Repair or replace.
Repair or replace.
Inspect, clean or replace.
Readjust.
HYDRAULIC SYSTEM TROUBLESHOOTING (Cont’d)
337 (S/N 515411001 & Above) Excavator
–2–7– Service Manual
Lever linkage incorrectly adjusted.
Track tension too tight.
Defective pump.
Travel motor counter balance spool
sticking.
Travel motor internal leakage
excessive.
Travel motor defective.
Travel motor gears defective.
Swivel joint defective.
Main relief valve pressure too low.
Pump compensator pressure too low.
Track tension too tight.
Main relief valve pressure too low.
Pump compensator.
Torque limiter.
Swivel joint leaking.
Travel motor counterbalance spool
sticking.
Pump margin too low.
Lever linkage incorrectly adjusted.
Swivel joint internal leakage
excessive.
Control valve internal leakage
excessive.
Low pump pressure.
Travel motor internal leakage
excessive.
Return line filter plugged.
Travel system inoperable.
Travel power.
Speed too slow.
Travel motor seal leakage.
PROBLEM CORRECTIONCAUSE
TROUBLESHOOTING THE TRAVEL CIRCUIT
Readjust.
Readjust.
Check, repair or replace.
Repair or replace.
Repair or replace.
Repair or replace.
Repair or replace.
Repair or replace.
Readjust or replace.
Readjust.
Readjust.
Readjust or replace.
Repair or replace.
Repair or replace.
Readjust.
Repair or replace.
Repair or replace.
Check, repair or replace.
Repair or replace.
Inspect, clean or replace.
HYDRAULIC SYSTEM TROUBLESHOOTING (Cont’d)
–2–8–
337 (S/N 515411001 & Above) Excavator
Service Manual
Lever linkage incorrectly adjusted.
Track tension not equal.
Travel motor internal leakage not
equal.
Travel motor counter balance spool
sticking.
Main relief valve pressure set too low.
Swivel joint internal leakage
excessive.
Control valve internal leakage not
equal.
Valve compensators not equal.
Track motor counterbalance valve
leakage excessive.
Hose damage.
Lever linkage unaligned.
Cylinder internal leakage excessive.
Control valve internal leakage
excessive.
Swivel joint internal leakage from
travel motor pressure circuit into blade
cylinder circuit.
Control valve defective.
Torque Limiter set too low.
Pump compensator set too low.
Switch defective.
Faulty pressure reducing valve.
Bad solenoid.
Machine not running straight.
Machine will not hold on slope or while
digging.
Blade drops while machine is moving.
High/low gear switch inoperative
(2–speed).
PROBLEM CORRECTIONCAUSE
TROUBLESHOOTING THE TRAVEL CIRCUIT (Cont’d)
Readjust.
Readjust.
Repair or replace.
Repair or replace.
Repair or replace.
Repair or replace.
Repair or replace.
Repair or replace.
Repair or replace.
Replace.
Readjust.
Repair or replace.
Repair or replace.
Repair or replace.
Replace.
Readjust.
Readjust.
Replace.
Repair or replace.
Replace.
HYDRAULIC SYSTEM TROUBLESHOOTING (Cont’d)
Revised Nov. 98
337 (S/N 515411001 & Above) Excavator
–2–9– Service Manual
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