5-2 Lower Mechanism: Travel Drive Unit Trouble Description External load works on the motor and cavitation and abnormal noise occur when a pumping action is performed.
Possible Cause
Countermeasure and Solution
Foreign matter gotten into the plunger prevents it from moving smoothly and providing counter balance function.
Disassemble the unit to remove the foreign matter. Check the degree of the damage by following the maintenance procedures. If it is still usable, re-assemble it. If it is no longer usable, replace it by using the base plate kit.
The spring of the plunger is damaged and the counter balance function is not provided.
Disassemble the unit to remove the foreign matter, replace the spring, and re-assemble the unit.
No spring is set in the plunger and the counter balance function is not provided.
Assemble a spring appropriately.
The spring of the check valve is damaged and the counter balance function is not provided.
Disassemble the unit to remove the foreign matter and then replace the spring.
No spring is set in the check valve and the counter balance function is not provided.
Assemble a spring appropriately.
The orifice of the pilot oil path is clogged with foreign matter and the counter balance function is not provided.
Disassemble the unit to remove the foreign matter and re-assemble it.
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