HYDRAULIC SYSTEM NBT40 SERVICE MANUAL
2-22 Published 8-01-2017 Control # 287-11
TROUBLE DIAGNOSIS
The following chart lists malfunctions which may occur
during equipment operation, the possible cause, and the
possible solution. These are not all inclusive but are
designed to help isolate the problem and should be checked
before calling
Manitowoc Crane Care.
O-RING FACE SEAL
O-RING BOSS
B
A
O-RING
FACE (REF)
O-RING
BOSS (REF)
A
B
O-RING FACE SEAL FITTING SIZE O-RING BOSS
THREAD
SIZE
B inches
(mm)
A inches
(mm)
TUBE
O. D.
MFGR’S
SIZE
CODE
A inches
(mm)
B inches
(mm)
THREAD
SIZE
9/16-18 .07 (1.78) .301 (7.64) .250 4 .351 (8.92) .072 (1.83) 7/16-20
11/16-16 .07 (1.78) .364 (9.24) .375 6 .458 (11.63) .078 (1.98) 9/16-18
13/16-16 .07 (1.78) .489(12.42) .500 8 .644 (16.36) .087 (2.21) 3/4-16
1-14 .07 (1.78) .614 (15.60) .625 10 .755 (19.18) .097 (2.46) 7/8-14
1 3/16-12 .07 (1.78) .739 (18.77) .750 12 .924 (23.47) .116 (2.95) 1 1/16-12
1 7/16-12 .07 (1.78) .926 (23.52) 1.000 16
1.171
(29.74)
.116 (2.95) 1 5/16-12
1 11/16-
12
.07 (1.78)
1.176
(29.87)
1.250 20
1.475
(37.46)
.118 (3.00) 1 5/8-12
2-12 .07 (1.78)
1.489
(37.82)
1.500 24
1.720
(43.69)
.118 (3.00) 1 7/8-12
NOTE:
Contact your National Crane Distributor or Manitowoc Crane Care for O-Ring boss seal kits.
CONDITION POSSIBLE CAUSE POSSIBLE SOLUTION
No hydraulic oil flows in
systems.
Low hydraulic oil level Fill reservoir.
Reservoir-to-pump suction lines broken or
restricted. Air entering at suction lines.
Pump not priming.
Check that all connections are tight and there are
no cracks. Clean, tighten, repair, or replace parts as
necessary.
Pump shaft sheared or disengaged.
If drive shaft is damaged or sheared, remove and
repair or replace as necessary
Internal contamination.
Drain, flush with recommended oil mixture, then
drain and refill system with recommended hydraulic
oil.
Reference Only
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