Jeep 200 Cherokee, Service Manual

Page: 1153 / 2119

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. 35). Refer to Engine Specifications for the
proper clearance.
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 mea-
sure the clearance as described in the previous steps.
The clearance indicated with the 0.025 mm (0.001
inch) undersize insert pair installed will determine if
this insert size or some other combination will provide
the specified clearance. FOR EXAMPLE: If the clear-
ance was 0.0762 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 original
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,
measure
crankshaft journal diameter with a
micrometer. If the journal diameter is correct, the
crankshaft bore in the cylinder block may be mis-
aligned, which requires cylinder block replacement or
machining to true bore.
If journals 1 through 5 diameters are less than
63.4517 mm (2.4981 inches), replace crankshaft or
grind crankshaft down to accept the appropriate
undersize bearing inserts.
Once the proper clearances have been obtained,
proceed to Crankshaft Main Bearing—Installation.
MAIN BEARING JOURNAL DIAMETER
(CRANKSHAFT REMOVED)
Remove the crankshaft from the cylinder block
(refer to Cylinder Block - Disassemble).
Clean the oil off the main bearing journal.
Determine the maximum diameter of the journal
with a micrometer. Measure at two locations 90°
apart at each end of the journal.
The maximum allowable taper and out of round is
0.013 mm (0.0005 inch). Compare the measured
diameter with the journal diameter specification
(Main Bearing Fitting Chart). Select inserts required
to obtain the specified bearing-to-journal clearance.
Once the proper clearances have been obtained,
proceed to Crankshaft Main Bearing—Installation.
Fig. 35 Measuring Bearing Clearance with
Plastigage
1 – PLASTIGAGE SCALE
2 – COMPRESSED PLASTIGAGE
9 - 24 2.5L ENGINE
XJ
SERVICE PROCEDURES (Continued)