Yanmar ViO12-2A, Service Manual

Page: 270 / 409

6. HYDRAULIC SYSTEM
6-
10
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5. Troubleshooting
Trouble Cause Measure
1. Motor does not rotate. 1) Malfunction of any hydraulic equipment
other than travel motor
Check the inlet pressure of the motor. Then, check
and repair or replace the other equipment.
2) Malfunction of hydraulic motor
(1) Pressure oil leakage due to exces-
sively worn sliding portion of internal
part
(2) Broken internal part
Replace the excessively worn part.
Replace the broken part or kit.
3) Malfunction of counterbalance valve
(Improper stroke of counterbalance
valve)
(1) Foreign matter caught in the valve
(2) Clogged choke
Remove the foreign matter, and repair or replace
the damaged part.
Clean the choke.
4) Malfunction of reduction gear
(1) Broken internal part
Replace the broken part or kit.
2. Travel speed is low or
machine cannot travel
straight.
1) Malfunction of any hydraulic equipment
other than travel motor
Check and repair or replace the equipment.
2) Malfunction of hydraulic motor
(1) Lowered volumetric efficiency due to
excessive worn
Replace the excessively worn part in the sliding
section.
3. Motor does not stop or
takes time to stop.
1) Malfunction of counterbalance valve
(Counterbalance valve does not return
normally.)
(1) Foreign matter caught in the valve
(2) Clogged choke
(3) Broken spring
Remove the foreign matter, and repair or replace
the damaged part.
Clean the choke.
Replace the spring.
4. Oil leakage. 1) Damaged O-ring Replace the O-ring.
2) Flaw in sealing surface of O-ring Repair the sealing surface or replace the O-ring.
3) Broken oil seal Replace the oil seal.
4) Excessively worn mechanical seal Replace the floating seat and the seal ring.
5) Loosened bolt or plug Retighten the bolt or the plug.
5. Machine slips exces-
sively on a slope.
1) Excessive oil leakage from hydraulic
motor
Replace the excessively worn part in the sliding
section.
2) Excessive oil leakage from counterbal-
ance valve
Replace the excessively worn part in the sliding
section.