Hitachi NR 90AD Technical Data And Service Manual page 22

Air leakage point
C) Nose 1
D) Nose 2
The O-ring (I.D 94.6) [18] of the Cylinder
Plate [17] or the O-ring (I.D. 59.6) [16] of
the Cylinder [15] is abnormal (broken or
flawed).
E)
Control Valve 1
The O-ring (1AP-10) [67] of the Valve
Piston [66] is abnormal (worn, broken or
flawed).
The lower O-ring (P-7) [65] of the Valve
Piston [66] is abnormal (worn, broken or
flawed).
The O-ring (P-18) [64] of Valve Bushing (B)
[63] is abnormal (broken or flawed).
The internal surface e of the valve cavity
of the Body Ass'y [24] is abnormal.
F)
Control Valve 2
The lower O-ring (I.D. 1.8) [69] of the
Plunger [70] is abnormal (worn, broken or
flawed).
Valve Bushing (A) [71] is abnormal (sliding
surface of the Plunger [70] is deformed or
flawed).
G) Cap
Gasket (B) [40] is damaged.
The Hex. Socket Hd. Bolt M5 x 16 [42] is loose.
Seal surface of the Body Ass'y [24] or the Cap [41] is abnormal (damaged, deformed or
flawed).
With control valve OFF
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Possible cause
With control valve ON
The O-ring (S-63) [32] of the Nose [29] or
the groove is abnormal (broken or flawed).
The Nylock Hex. Socket Hd. Bolt M8 x 30
[30] is loose.
The Piston Bumper [31] is abnormal
(portion d is damaged, deformed or
cracked).
The Piston [13] is abnormal (driver blade is
deformed or seal surface is deformed).
The upper O-ring (P-7) [65] of the Valve
Piston [66] is abnormal (worn, broken or
flawed).
The Feed Piston O-ring (I.D. 14) [62] of
Valve Bushing (B) [63] is abnormal (broken
or flawed).
The internal surface f of the valve cavity
of the Body Ass'y [24] is abnormal.
The upper O-ring (I.D 1.8) [69] of the
Plunger [70] is abnormal (worn, broken or
flowed).
The Valve Piston [66] is abnormal (sliding
surface of the Plunger [70] is deformed or
flawed).