TM 5-3895-346-14
CRANKSHAFT OIL SEALS
ENGINE OVERHAUL
CRANKSHAFT OIL SEALS
An oil seal is used at each end of the crankshaft to retain the lubricating oil in the crankcase. The sealing lips of
the oil seals are held firmly, but not tight, against the crankshaft seal- ing surfaces by a coil spring.
The front oil seal is pressed into the lower front cover on in-line engines (Fig. 1).
A single-lip oil seal is used at the rear end of the crankshaft of most industrial engines. The rear oil seal is
pressed into the flywheel housing (Fig. 2).
Oil leaks indicate worn or damaged oil seals. Oil seals may become worn or damaged due to improper
installation, excessive main bearing clearances, excessive flywheel housing bore runout, or grooved sealing
surfaces on the crankshaft. To prevent a repetition of any oil seal leaks, these conditions must be checked and
corrected.
Remove Crankshaft Oil Seals
Remove the engine front cover (Engine Front Cover (Lower)), outboard bearing support or the flywheel housing
(Fly- wheel Housing) and remove the oil seals as follows:
1.
Support the forward face of the front cover, or the outboard bearing support, on two woodblocks
next to the oil seal bore. Then press or drive the oil seal out of the front cover or the outboard bearing support.
Discard the oil seal.
2.
Support the forward face of the flywheel housing on in-line engines on two woodblocks next to the
oil seal bore. Then press or drive the oil seal out of the housing. Discard the oil seal.
3.
Clean the oil seal bore in the front cover, outboard bearing support, or flywheel housing thoroughly
before installing a new oil seal.
When necessary, an oil seal may be re- moved without removing the front cover, outboard bearing support, or
flywheel
Figure 1. Crankshaft Front Oil Seal
Figure 2. Crankshaft Rear Oil Seal
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