DETROIT DIESEL 53
Main Bearings
1.3.4
Fig. 6 Comparison of Main Bearing Shells
Inspection
Bearing failures may result from deterioration (acid
3. Remove one main bearing cap at a time and inspect
formation) or contamination of oil or loss of oil. An
the bearing shells as outlined under lnspeciion.
analysis of the lubricating oil may be required to
Reinstall each hearing shell and bearing cap before
determine if corrosive acid and sulphur are present
removing another bearing cap.
which cause acid etching, flaking and pitting. Bearing
seizure may be due to low oil or no oil.
a. To remove all except the rear main bearing shell,
insert a 1/4" x 3/4" bolt with a 1/2" diameter
Check the oil filter elements and replace them if
and 1/16" thick head (made from a standard
necessary. Also check the oil by-pass valve to make
bolt) into the crankshaft journal oil hole. Then
sure it is operating freely.
revolve the shaft to the right (clockwise) and roll
the bearing shell out of position as shown in
Fig. 4. The head of the bolt must not extend
scoring, pitting, flaking, etching, loss of babbitt or
beyond the outside diameter of the bearing shell.
signs of overheating (Fig. 6). The lower bearing shells.
which carry the load, will normally show signs of
b. Remove the rear main bearing upper shell by
distress before the upper bearing shells.
tapping on the edge of the bearing with a small
curved rod. revolving the crankshaft at the same
Inspect the backs of the bearing shells for bright spots
time to roll the bearing shell out as shown in Fig. 5.
which indicate they have been moving in the bearing
caps or bearing supports. If such spots are present.
c. The lower halves of the crankshaft thrust washers
discard the bearing shells.
will he removed along with the rear main bearing
cap. The upper halves of the washers can be re-
Measure the thickness of the bearing shells at point
moved for inspection by pushing on the ends of the
washers with a small rod. forcing them around and
and 8. Tool J 4757. placed between the bearing shell
out of the main bearing support.
and a micrometer. will give an accurate measurement.
SEC. 1.3.4 Page 3
April, I974
