Mitsubishi Heavy Industries L2, Service Manual

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75 / 155 Service Manual Mitsubishi L-Series diesel engines
Version 08/2004
CRANKSHAFT
ENGLISH
ENGINE MAIN PARTS
16.3.1 Checking the crankshaft for wear
To check the crankpins and main journals for
cylindricity and roundness, measure the diameter of
each crankpin and main journal at two places 1 and 2 in
directions “A” and “B” for a total of 4 measurements in
the figure at right. If necessary, regrind the crankpins
and main journals to the next under size. If any
crankpin or main journal has been worn out beyond the
service limit, replace the crankshaft.
16.3.2 Inspection of crankshaft oil
clearance
Oil clearance is calculated by subtracting the diameter
of main journal and crankpin from the inside diameter
of main bearing and rod bearing. To check the main
bearings and rod bearings for tapering wear and out-of-
round wear, inside diameter of each main bearing and
rod bearing should be measured, after its bearing-cap
is fastened to the specified torque, at two places along
the bearing, in two directions “A” and “B” each place, as
shown in the figure at right. If necessary, replace the
worn bearing with new one. If oil clearance still
exceeds the service limit, regrind the crankshaft to the
next under size and replace the bearing with one of the
corresponding under size.
Figure 80 Measuring ring gap
Ring Standard Service Limit
Main journal
diameter
43 [1.6929] -0.70 [-0.0276]
Crankpin
diameter
40 [1.5748] -0.70 [-0.0276]
Table 31 Diameter of crankpin and main journal
(mm [in.])
Ring Standard Service Limit
0.25 US
42.715 to 42.730
[1.6817 to 1.6823]
39.715 to 39.730
[1.5636 to 1.5642]
0.50 US
42.465 to 42.480
[1.6718 to 1.6724]
39.465 to 39.480
[1.5537 to 1.5543]
Table 32 Undersize diameters (mm [in.])
Figure 81 Measuring main bearing I. D.
CAUTION
A crankshaft, which has been seized, cannot be
reground to any under size.