DETROIT DIESEL 53
Main Bearings 1.3.4
crankshaft. See Section 1.3 under Crankshaft Inspection for removal of ridges and inspection of the crankshaft.
Do not replace one main bearing shell alone. If one bearing shell requires replacement, install both new upper and lower
bearing shells. Also, if a new or reground crankshaft is to be used, install all new bearing shells.
Bearing shells are available in .010", .020"and .030 " undersize for service with reground crankshafts. To determine the
size bearings required, refer to Crankshaft Grinding in Section 1.3.
Bearings which are .002" undersize are available to compensate for slight journal wear where it is unnecessary to regrind
NOTE: Bearing shells are NOT reworkable from one undersize to another under
Inspect the crankshaft thrust washers. If the washers are scored or worn excessively or the crankshaft end play is
excessive, they must be replaced. Improper clutch adjustment can contribute to excessive wear on the thrust washers.
Inspect the crankshaft thrust surfaces. Refer to Install Crankshaft in Section 1.3. If, after dressing or regrinding the thrust
surfaces, new standard size thrust washers do not hold the crankshaft end play within the specified limits, it may be
necessary to install oversize thrust washers on one or both sides of the rear main bearing. A new standard size thrust
washer is .1190" to .1220" thick. Thrust washers are available in .005 " and .010" oversize.
Install Main Bearing Shells (Crankshaft in Place)
Make sure all of the parts are clean. Then apply clean engine oil to each crankshaft journal and install the upper main
bearing shells by reversing the sequence of operations given for removal.
The upper and lower main bearing shells are not alike; the upper shell is grooved and drilled for lubrication -- the lower
shell is not. Be sure to install the grooved and drilled bearing shells in the cylinder block and the plain bearing shells in
the bearing caps, otherwise the oil flow to the bearings and to the upper end of the connecting rods will be blocked off.
Used bearing shells must be reinstalled on the same journal from which they were removed.
1. When installing an upper main bearing shell with the crankshaft in
place, start the plain end of the bearing shell around the crankshaft
journal so that, when the bearing is in place, the tang will fit into the
groove in the bearing support.
2. Install the lower main bearing shell so that the tang on the bearing
fits into the groove in the bearing cap.
3. Assemble the crankshaft thrust washers (Fig. 9) before installing
the rear main bearing cap. Clean both halves of each thrust washer
carefully and remove any burrs from the washer seats -- the slightest
burr or particle of dirt may decrease the clearance between the washers
and the crankshaft beyond the specified limit. Slide the upper halves of
the thrust washers into place. Then assemble the lower halves over the
dowel pins in the bearing cap.
NOTE: The main bearing caps are bored in position
and marked 1, 2, 3, etc. They must be installed in their
original positions with the marked side of each cap
facing the same side of the cylinder block that carries
the engine serial number.
Fig. 9 - Crankshaft Thrust Washers in Place