DETROIT DIESEL 53
may be cleaned up with emery cloth and crocus cloth in
the same manner as- detailed for the crankshaft
If the crankshaft cannot be cleaned up
satisfactorily, the oil seals may be repositioned in the
flywheel housing and front cover as outlined in Section
Check the crankshaft thrust surfaces for excessive wear
or grooving. If only slightly worn, the surfaces may be
dressed with a stone. Otherwise, it will be necessary to
regrind the thrust surfaces.
Check the oil pump drive gear and the crankshaft timing
gear for worn or chipped teeth. Replace the gears, if
Fig. 3. - Typical Ridging of Crankshaft
crankshaft with fuel oil and dry it with compressed air.
Inspect the crankshaft for cracks as outlined under
Then, reinstall the plugs.
Inspection for Cracks.
Inspect the keyways for evidence of cracks or wear.
Replace the crankshaft, if necessary.
Support the crankshaft on its front and rear journals on
If the crankshaft has been subjected to excessive
V-blocks or in a lathe and check the alignment at the
overheating, the heat treatment will be destroyed and a
adjacent intermediate main journals with a dial indicator.
new crankshaft should be installed.
The maximum runout on the intermediate journals must
Used crankshafts will sometimes .show a certain
not exceed .002" total indicator reading.
amount of ridging caused by the groove in the upper
main bearing shell or lower connecting rod bearing shell
(Fig. 3). Ridges exceeding 1.0002" must be removed.
If the ridges are not removed, localized high unit
pressures on new bearing shells will result during engine
The ridges may be removed by working crocus cloth,
On the 6V crankshaft, when the runout on the adjacent
wet with fuel oil, around the circumference of the
journals is in opposite directions, the sum must not
crankshaft journal. If the ridges are greater than .0005",
exceed .003" total indicator reading. When the runout
first use 120 grit emery cloth to clean up the ridge, 240
on the adjacent journals is in the same direction, the
grit emery cloth for finishing, and wet crocus cloth for
difference must not exceed .003" total indicator reading.
polishing. Use of a piece of rawhide or other suitable
When high spots of runout on the adjacent journals are
rope wrapped around the emery cloth or crocus cloth
at right angles to each other, the sum must not exceed
and drawn back and forth will minimize the possibility of
.004" total indicator reading, or .002" on each journal. If
an out-of-round condition developing (keep the strands
the runout limit is greater than given above, the
of rawhide apart to avoid bind). If rawhide or rope is not
crankshaft must be replaced.
used, the crankshaft should be rotated at intervals. If
the ridges are greater than .001", the crankshaft may
Measure all of the main and connecting rod bearing
have to be reground.
journals. Measure the journals at several places on the
circumference so that taper, out-of-round and bearing
Carefully inspect the front and rear end of the crankshaft
clearances can be determined. If the crankshaft is worn
in the area of the oil seal contact surface for evidence of
so that the maximum connecting rod journal-to- bearing
a rough or grooved condition. Any imperfections of the
shell clearance (with new shells) exceeds .0041" (V-type
oil seal contact surface will result in oil leakage at this
engine), or the main bearing journal-to-bearing shell
Slight ridges on the crankshaft oil seal contact surfaces
1972 General Motors Corp.
SEC. 1.3 Page 3