Wrangler 4WD L4-150 2.5L VIN P MFI (1998)
Crankshaft Main Bearing: Service and Repair
Fitting Bearings
INSPECTION
Main Bearing Wear Patterns
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.
NOTE: If any of the crankshaft journals are scored, remove the engine for crankshaft repair.
Inspect the back of the inserts for fractures, scrapings or irregular wear patterns.
Inspect the upper insert locking tabs for damage.
Replace all damaged or worn bearing inserts.
FITTING BEARINGS (CRANKSHAFT INSTALLED)
The main bearing caps, numbered (front to rear) from 1 through 5 have an arrow to indicate the forward 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 identified 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.
Measuring Bearing Clearance With Plastigage
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 in.) undersize insert to reduce the clearance by 0.013 mm (0.0005 in.). Never use a pair of bearing inserts with greater than a
0.025 mm (0.001 in.)difference in size).
