F
OR
M
ODELS
: JGI, JGM, JGN, JGP
AND
JGQ
S
ECTION
5 - M
AINTENANCE
PAGE 5-20
(0.25 mm) TIR.
F
IGURE
5-16 F
AN
S
HAFT
Main Bearings - Removal and Installation w/Crankshaft
Removed
Do not remove a main bearing cap to check for bearing wear, if cap is removed it is recom-
mended that a new bearing is installed, i.e.
DO NOT REUSE BEARING SHELLS
. Deter-
mine bearing wear by checking actual jack and crankshaft thrust clearances against the
clearance limits given in Table 1-3 on page 1-10. See "Main Bearings - Checking Clear-
ances" on Page 5-14. High copper content in the oil analysis may be an indication of main
and/or connecting rod bearing wear, and/or chain idler, crosshead, connecting rod bushings
wear (excessive use of anti-seize lubricates can also elevate copper content in the oil analy-
sis).
There are notches in the frame and bearing cap for the bearing tabs in order to position and
maintain the position of the bearing halves. Check the new bearing shells for handling dam-
age, scratches, burrs, and loose material at the tab.
DO NOT RUB BEARING SURFACE
WITH FINGERNAIL
. The bearing shells must be absolutely clean. Be sure that bearing shell
part numbers on both halves match.
The old bearings halves are easily slid out, tab end first. Be sure both the main bearing sad-
dles and crankshaft are absolutely clean, and free from nicks and burrs. New bearings are to
be slid in (untabbed end first), and snapped into place. Locate tabs in the notches in the
bearing saddles and bearing caps.
On JGI models, remove the carrier bearing using a hydraulic press or jack. Remove the
frame bearing using a hydraulic jack. A pushing tool with a shoulder is needed. Install new
bearings by cooling the bushings and using the hydraulic tools. Do not use a hammer to
force the bushings into place as this will distort the bearing's bore. The new bushings are to
be installed into the connecting rod by cooling the bushing in a 95 percent alcohol solution
with dry ice solution. The bushing needs to be left in the solution long enough to reach the
same temperature as the solution, about -110°F (-80°C). Oil holes on bearing must be
aligned with holes in frame and carrier. The bushings must be pressed 3/16 in. (4.8 mm)
Crankshaft
Wrench Flat
Fan
Shaft
Loctite this
end only
Chain
Sprocket
Stud
Fan Shaft
Keyway
Check Fan Shaft
Runout here
