Connecting Rod Bearing Selection Chart-Four-Cylinder Engines; Connecting Rod Bearing Selection Chart-Inline Six-Cylinder Engines - Jeep cherokee 1989 Owner's Manual

2D-20
2 Bearing failure occurs because of lack of lubrication, the presence
of dirt or other foreign particles, overloading the engine and corrosion.
Regardless of the cause of bearing failure, it must be corrected before
the engine is reassembled to prevent it from happening again.
3 When examining the bearings, remove them from the engine block,
the main bearing caps, the connecting rods and the rod caps and lay
them out on a clean surface in the same general position as their loca-
tion in the engine. This will enable you to match any bearing problems
with the corresponding crankshaft journal.
4
Dirt and other foreign particles get into the engine in a variety of
ways. It may be left in the engine during assembly, or it may pass
through filters or the PCV system. It may get into the oil, and from
there into the bearings. Metal chips from machining operations and
normal engine wear are often present. Abrasives are sometimes left
in engine components after reconditioning, especially when parts are
not thoroughly cleaned using the proper cleaning methods. Whatever
the source, these foreign objects often end up embedded in the soft
bearing material and are easily recognized. Large particles will not em-
bed in the bearing and will score or gouge the bearing and journal. The
best prevention for this cause of bearing failure is to clean all parts
thoroughly and keep everything spotlessly clean during engine
assembly. Frequent and regular engine oil and filter changes are also
recommended.
5
Lack of lubrication (or lubrication breakdown) has a number of inter-
Crankshaft Maln Bearlng Journal 2-3-44
Color Code and Dlameter In
Yellow -
(53.2257 53.2079 mm) (Standard)
Orange -2.0948 to 2.0941
(53.2079
-
Black 2.0941 to 2.0643
(53.1801 to 53.1723 nim) (0.0014 Underslze)
-
Red 2.0855 to 2.0848
(53.9717 to 53.9539 mm) (0.010 Underslze)
Connecting Rod Bearing Journal
Color Code and Diameter
(Journal Size)
Yellow - 53.2257 53.2079
-
(2.0955 2.0948 in.)
(Standard)
-
Orange - 53.2079 53.1 901
-
(2.0948 2.0941 in.)
(0.0007 Undersize)
-
Black - 53.1 901 53.1 723
(2.0941 2.0943 in.)
(0.001 4 Undersize)
-
Red - 53.971 7 53.9539 mm
-
(2.0855 2.0848 in.)
(0.01 0 Undersize)
The Motor Manual Guy
Chapter 2 Part D General engine overhaul procedures
-
Yellow
Yellow
-
Black
-
Red
.
Connecting rod bearing selection chart
Upper lnsert Size
-
Yellow Standard
-
Yellow Standard
mm
-
mm Black 0.025
Undersize
-
Red 0.254
Undersize
related causes. Excessive heat (which thins the oil), overloading (which
squeezes the oil from the bearing face) and oil leakage or throw off
(from excessive bearing clearances, worn oil pump or high engine
speeds) all contribute to lubrication breakdown. Blocked oil passages,
which usually are the result of misaligned oil holes in a bearing shell,
will also oil starve a bearing and destroy it. When lack of lubrication
is the cause of bearing failure, the bearing material is wiped or extruded
from the steel backing of the bearing. Temperatures may increase to
the point where the steel backing turns blue from overheating.
6 Driving habits can have a definite effect on bearing life. Full throttle,
low speed operation (lugging the engine) puts very high loads on bear-
ings, which tends t o squeeze out the oil film. These loads cause the
bearings to flex, which produces fine cracks in the bearing face (fatigue
failure). Eventually the bearing material will loosen in pieces and tear
away from the steel backing. Short trip driving leads to corrosion of
bearings because insufficient engine heat is produced t o drive off the
condensed water and corrosive gases. These products collect in the
engine oil, forming acid and sludge. As the oil is carried t o the engine
bearings, the acid attacks and corrodes the bearing material.
7
bearing failure as well. Tight fitting bearings leave insufficient bearing
oil clearance and will result in oil starvation. Dirt or foreign particles
trapped behind a bearing insert result in high spots on the bearing which
lead to failure.
Upper Insert Slza
Standard
Standard
0.001-Inch (0.025 rnrn) Undersize
-
four-cylinder engines
Bearing Insert Color Code
Yellow
Black
mm Black
(0.001 in.)
Red
mm (0.010 in.)
-
Lower Insert Slze
-
Yellow Standard
-
0.001-Inch (0.025 rnm) Undersize
Black
0.001-inch (0.025 mrn) Underslze
Black
Red
Lower lnsert Size
-
Standard
-
0.025 mm (0.001 in.)
Undersize
-
0.025 mm (0.001 in.)
Undersize
-
0.245 (0.010 in.)
Undersize