TM 5-3895-346-14
MAIN BEARINGS
3.
Remove one main bearing cap at a time and inspect the bearing shells as outlined under
Inspection. Reinstall each bearing shell and bearing cap before re-moving another bearing cap:
a.
To remove all except the rear main bearing shell, insert a 1/4 x 3/4-inch long bolt with a 1/2-inch
diameter and 1/16-inch thick head (made from a standard bolt) into the crank- shaft journal oilhole. Then
revolve the shaft to the right (clockwise) and roll the bearing shell out of position as shown in Fig. 2. The head
of the bolt must not extend beyond the outside diameter of the bearing shell.
b.
Remove the rear main bearing upper shell by tapping on the edge of the bearing with a small
curved rod, revolving the crankshaft at the same time to roll the bearing shell out as shown in Fig. 3.
c.
The lower halves of the crank- shaft thrust washers will be removed along with the rear main
bearing cap. The upper halves of the washers can be removed for inspection by pushing on the ends of the
washers with a small rod, forcing them around and out of the main bearing support.
Figure 2. Removing Upper Main Bearing
Shell (Except Rear Main)
Figure 3. Removing Upper Rear Main
Bearing Shell
Inspection
Bearing failures may result from deterioration (acid formation) or contamination of the oil or loss of oil. An
analysis of the lubricating oil may be required to determine if corrosive acid and sulfur are present which cause
acid etching, flaking, and pitting.
Bearing seizure may be due to low oil or no oil.
Check the oil filter elements and re- place them if necessary. Also check the oil bypass valve to make sure it is
operating freely.
120
