PC800, 850-8 37
40 Troubleshooting SEN00794-02
H-26 Large shock is made when upper structure stops swinging
Failure
phenomenon
• Large shock is made when upper structure
stops swinging
(1) Large shock is made when the upper structure stops
swinging in both directions.
Relative
information
• When carrying out the following troubleshooting, set the working mode in the P-mode and turn the
swing lock switch OFF.
Possible causes
and standard
value in normal
state
Cause Standard value in normalcy and references for troubleshooting
1
Malfunction of swing hold-
ing brake solenoid valve
aKeep the engine stopped for the preparations, and run it at high idle
during troubleshooting.
Left work equipment control lever Solenoid valve outlet pressure
Neutral (After 5 seconds or more) 0 MPa {0 kg/cm
2
}
Operated to swing (in either direc-
tion)
Min. 2.74 MPa
{Min. 28 kg/cm
2
}
2
Malfunction of swing motor
(parking brake)
The parking brake of the swing motor may malfunction. Check it directly.
3
Wrong adjustment or mal-
function of swing motor
(safety valve)
aKeep the engine stopped for the preparations, and run it at high idle
during troubleshooting.
Left work equipment control lever Swing relief pressure
Swing relief (in either direction)
28.9 MPa
{295 kg/cm
2
}
If the oil pressure is still abnormal after adjustment, the safety valve may
malfunction. Check the safety valve directly.
4
Swing motor (motor unit)
defective internally
The motor unit of the swing motor may have a defect in it. Check it
directly.
5
Swing machinery
defective internally
Swing machinery may have a defect in it. Check it directly. (The swing
machinery can be checked by abnormal sound, abnormal heating, metal
dust in the drained oil, etc.)
Failure
phenomenon
• Large shock is made when the upper struc-
ture stops swinging.
(2) Large shock is made when the upper structure stops
swinging in only 1 direction.
Relative
information
• When carrying out the following troubleshooting, set the working mode in the P-mode and turn the
swing lock switch OFF.
Possible causes
and standard
value in normal
state
Cause Standard value in normalcy and references for troubleshooting
1
Malfunction of left PPC
valve (swing circuit)
aKeep the engine stopped for the preparations, and run it at high idle
during troubleshooting.
Left work equipment control lever PPC valve output pressure
Neutral 0 MPa {0 kg/cm
2
}
Swing RIGHT/LEFT stroke end
2.9 MPa
{30 kg/cm
2
}
2
Malfunction of swing
control valve (spool)
The spool of the swing control valve may malfunction. Check it directly.
3
Malfunction of swing motor
(suction valve)
The suction valve of the swing motor may malfunction. Check it directly.
(The suction valves of the right and left swing motors can be checked by
exchanging them with each other and seeing the change of the phe-
nomenon.)
+2.5
–0.5
+25
–5
+0.8
–0.2
+8
–2
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