Fitting Crankshaft Main Bearings - Jeep cherokee 2000 Service Manual

XJ
SERVICE PROCEDURES (Continued)
Fig. 34 Checking Connecting Rod Side Clearance—

FITTING CRANKSHAFT MAIN BEARINGS

INSPECTION
Wipe the inserts clean and inspect for abnormal
wear patterns and for metal or other foreign material
imbedded in the lining. Normal main bearing insert
wear patterns are illustrated (Fig. 35). In general the
lower bearing half will have a heaver wear pattern.
Fig. 35 Main Bearing Wear Patterns
1 – UPPER INSERT
2 – NO WEAR IN THIS AREA
3 – LOW AREA IN BEARING LINING
4 – LOWER INSERT
NOTE: If any of the crankshaft journals are scored,
remove the engine for crankshaft repair.
Inspect the back of the inserts for fractures, scrap-
ings or irregular wear patterns.
Inspect the upper insert locking tabs for damage.
Replace all damaged or worn bearing inserts.
Typical
FITTING BEARINGS (CRANKSHAFT INSTALLED)
The main bearing caps, numbered (front to rear)
from 1 through 7 have an arrow to indicate the for-
ward position. The upper main bearing inserts are
grooved to provide oil channels while the lower
inserts are smooth.
Each bearing insert pair is selectively fitted to its
respective journal to obtain the specified operating
clearance. In production, the select fit is obtained by
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 (Fig. 36) on the
adjacent cheek or counterweight towards the rear of
the crankshaft (flange end). The rear main journal, is
identified by a color-coded paint mark on the crank-
shaft 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. Refer to the
Bearing Insert Pair Chart.
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
4.0L ENGINE 9 - 83