H-21 The Bucket Comes To Operate Slowly In The Midst Of Tilting-Back; H-22 The Bucket Cylinder Cannot Hold Down The Bucket; H-23 Hydraulic Drifts Of The Bucket Occur Often; The Bucket Wobbles During Travel With Load (The Work Equipment Valve Is Set To "Hold") - Komatsu WA250-6 Shop Manual

SEN03849-00

H-21 The bucket comes to operate slowly in the midst of tilting-back

Inspection before diagnosis
Deformation of bucket cylinder in appearance
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Cause
Expansion of bucket cylinder tube or damage inside
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For other abnormal phenomena during bucket operation, see "H-20. The bucket moves slowly or the tilt-
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ing-back force is insufficient."

H-22 The bucket cylinder cannot hold down the bucket

See "H-20. The bucket moves slowly or the tilting-back force is insufficient."
Inspection before diagnosis
Is the stroke of the bucket control lever appropriate?
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Cause
Defective seat of suction valve on the bucket cylinder rod side of work equipment valve
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Oil leak from bucket cylinder piston seal
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H-23 Hydraulic drifts of the bucket occur often

Ask the operator about the following:
Have hydraulic drifts come to occur often suddenly? o Wastes pinched in valve or damage of parts
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Have hydraulic drifts come to occur often gradually? o Wear of parts
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Inspection before diagnosis
Is the bucket lever (PPC valve) at the neutral position? o Seizure of link bushing or the spool detent is
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defective
Check of Abnormality
Refer to the criterion value table and check if the hydraulic drift of the bucket occurs often practically
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Cause
Oil leak in bucket cylinder
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Improper adhesion of safety valve (With suction valve) on the bottom side
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Improper oil tight of bucket spool
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H-24 The bucket wobbles during travel with load
(The work equipment valve is set to "HOLD")
Inspection before diagnosis
Pin of work equipment linkage and "play of bushing" (Is any abnormal noise heard?)
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Cause
Defective seal of bucket cylinder piston
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Defective operation of safety valve (With suction valve) on bucket cylinder rod side. For other abnormal
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phenomena, refer to diagnoses for relevant abnormal phenomena.
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40-500
500 Troubleshooting of hydraulic and mechanical system (H-mode)
H-21 The bucket comes to operate slowly in the midst of tilting-back
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WA250, 250PZ-6