Jeep Wrangler 1997 Manual page 723

TJ
SERVICE PROCEDURES (Continued)
using various-sized color-coded bearing insert pairs
as listed in the Main Bearing Fitting Chart. The
bearing color code appears on the edge of the insert .
The size is not stamped on bearing inserts used
for engine production .
The main bearing journal size (diameter) is identi-
fied by a color-coded paint mark on the adjacent
cheek . The rear main journal, is identified by a color-
coded paint mark on the crankshaft rear flange.
When required, upper and lower bearing inserts of
different sizes may be used as a pair. A standard size
insert is sometimes used in combination with a 0.025
mm (0.001 inch) undersize insert to reduce the clear-
ance by 0.013 mm (0.0005 inch). Never use a pair
of bearing inserts with greater than a 0 .025 mm
(0.001 inch) difference in size (Fig. 17).
Fig. 17 Bearing Insert Pairs
J9109-179
NOTE : When replacing inserts, the odd size inserts
must be either all on the top (in cylinder block) or
all on the bottom (in main bearing cap) .
Once the bearings have been properly fitted, pro-
ceed to Crankshaft Main Bearing-Installation.
BEARING-TO-JOURNAL CLEARANCE (CRANKSHAFT
INSTALLED)
When using Plastigage, check only one bearing
clearance at a time.
Install the grooved main bearings into the cylinder
block and the non-grooved bearings into the bearing
caps.
Install the crankshaft into the upper bearings dry.
Place a strip of Plastigage across full width of the
crankshaft journal to be checked .
Install the bearing cap and tighten the bolts to 108
N-m (80 ft. lbs .) torque .
NOTE : DO NOT rotate the crankshaft . This will
cause the Plastigage to shift, resulting in an inaccu-
rate reading. Plastigage must not be permitted to
crumble. If brittle, obtain fresh stock.
Remove the bearing cap. Determine the amount of
clearance by measuring the width of the compressed
Plastigage with the scale on the Plastigage envelope
(Fig. 18). Refer to Engine Specifications for the
proper clearance .
COMPRESSED
PLASTIGAGE
PLASTIGAGE
SCALE
4 .OL ENGINE
9 - 61
J9009-42
Fig. 18 Measuring Bearing Clearance with
Plastigage
Plastigage should indicate the same clearance
across the entire width of the insert. If clearance var-
ies, it may indicate a tapered journal or foreign
material trapped behind the insert .
If the specified clearance is indicated and there are
no abnormal wear patterns, replacement of the bear-
ing inserts is not necessary. Remove the Plastigage
from the crankshaft journal and bearing insert . Pro-
ceed to Crankshaft Main Bearing-Installation.
If the clearance exceeds specification, install a pair
of 0.025 mm (0.001 inch) undersize bearing inserts
and measure the clearance as described in the previ-
ous steps.
The clearance indicate with the 0.025 mm (0 .001
inch) undersize insert pair installed will determine if
this insert size or some other combination will pro-
vide the specified clearance . FOR EXAMPLE : If the
clearance was Og762 mm (0.003 inch) originally, a
pair of 0 .0254 mm (0 .001 inch) undersize inserts
would reduce the clearance by 0 .0254 mm (0.001
inch). The clearance would then be 0.0508 mm (0.002
inch) and within the specification . A 0.051 mm (0.002
inch) undersize bearing insert and a 0 .0254 mm
(0 .001 inch) undersize insert would reduce the origi-
nal clearance an additional 0.0127 mm (0.0005 inch) .
The clearance would then be 0 .0381 mm (0.0015
inch).
CAUTION : Never use a pair of inserts that differ
more than one bearing size as a pair .
FOR EXAMPLE : DO NOT use a standard size
upper insert and a 0.051 mm (0.002 inch) undersize
lower insert.
If the clearance exceeds specification using a pair
of 0 .051 mm (0.002 inch) undersize bearing inserts,
Insert
Correct Incorrect
Upper
Standard Standard
Lower
0025 mm (0 .001 in .)
0.051 mm (0 .002 in .)
Undersize
Undersize