necessary. Piston and connecting rod assemblies of locomotives used for switching may require more
frequent repair.
a. Pistons. Before pulling the piston, remove any ridge on the liner with a reamer. Gaps of
rings can be measured most accurately while holding them in place in the liner. After the piston is
removed, clean any chips out of the crankcase. Clean pistons and inspect them for defects; replace first
and second compression rings. Examine piston pin and bearing for wear, cracks, or chips.
b. Connecting rods. Clean and inspect connecting rods, making certain that oil passages are
open. Replace any defective rods. Examine connecting rod studs, bolts, and nuts. If piston seizure
occurs before removal of connecting rod stud or bolt nuts, remove cotter pins and check tightness of nuts
to determine if bolts have been stretched. If they are stretched, they are not safe for further use.
2.4.
BEARINGS
Never force bearings or bearing shells as the bearing face may be scratched or the shell distorted.
Note the identification mark on the shell so that it can be replaced correctly. Bearings should always be
replaced in the same shells because their locations can determine how they are worn.
To remove bearing shells, take off the crankcase doors opposite the shells to be removed and
rotate the engine so that the skirt of the piston in the opposite bank of cylinders has completely entered
its liner. Unscrew the connecting rod nuts and bolts, taking out the cap with its bearing. Tap the cap
from the rod. Figure 2.1 shows the bearing shells removed and disconnected so that the bearings can be
removed.
After bearings are replaced, examine grooves and oil holes to make sure that these passages are
free of obstruction. Always make a running test before releasing the assembly for service. Idle the
engine a few minutes and then feel the bearing shell. If it is hot, smooth the high spots on the bearing
and repeat the test. With a switching locomotive, a test should be made consisting of light switching
duty for the first 8 hours followed by an inspection of the bearings at the end of the test.
Inspection and maintenance procedures for bearings in general can be illustrated by those for
bearings of the connecting rod, crankshaft, axle, and journal.
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