H-14 When Rising, The Lift Arm Comes To Move Slowly At Specific Height; The Lift Arm Cylinder Cannot Hold Down The Bucket (The Bucket Rises In The Air); H-16 Hydraulic Drifts Of The Lift Arm Occur Often; H-17 The Lift Arm Wobbles During Operation - Komatsu WA250-6 Shop Manual

SEN03849-00

H-14 When rising, the lift arm comes to move slowly at specific height

Inspection before diagnosis
Deformation of lift arm cylinder in appearance
q
Cause
Expansion of lift arm cylinder tube or damage inside
q
a For other abnormal phenomena during lift arm rise, see "H-13. The lift arm moves slowly or the lift arm
rising force is insufficient."
H-15 The lift arm cylinder cannot hold down the bucket (The bucket
rises in the air)
See "H-13. The lift arm moves slowly or the lift arm rising force is insufficient."
Inspection before diagnosis
Is the stroke of the lift arm control lever appropriate?
q
Cause
Defective seat of suction valve on the lift arm cylinder rod side of work equipment valve
q
Oil leak from lift arm cylinder piston seal
q

H-16 Hydraulic drifts of the lift arm 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
q
Have hydraulic drifts come to occur often gradually? o Wear of parts
q
Inspection before diagnosis
Is the lift arm spool at the neutral position? o The spool detent is defective
q
Diagnosis and Cause
Does any leaking noise occur inside the lift arm cylinder when hydraulic drift is measured? o The cylin-
q
der packing is defective

H-17 The lift arm wobbles during operation

The bucket and the lift arm moves up and down as the topography goes in digging or leveling with the lift arm
control lever in the "HOLD" position.
Diagnosis and Cause
Check at first the hydraulic drift and if the lift arm cylinder can lift the machine
1. When the hydraulic drift is more than the standard value, see "H-16. Hydraulic drifts of the lift arm occur
often."
2. When the lift arm cylinder cannot lift the machine, see "H-15. The lift arm cylinder cannot hold down the
bucket."
3. When the lift arm cylinder comes to enable to lift the machine after the lift arm is operated several times
with the normal hydraulic drift and after the lift arm cylinder operates to full stroke o The cause is vac-
uum generated inside the cylinder
a Frequent hydraulic drifts o The suction valve on the lift arm cylinder rod side is defective
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40-500
500 Troubleshooting of hydraulic and mechanical system (H-mode)
H-14 When rising, the lift arm comes to move slowly at specific height
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WA250, 250PZ-6