Rear Main Bearing Oil Seal - Jeep 1979 CJ-5 Technical & Service Manual

1B-66 ENGINES
N O T E : Plastigage must not crumble. If brittle, obtain
fresh stock.
(5) Install bearing cap and tighten retaining screws
to 100 foot-pounds (136 N®m) torque.
N O T E : Do not rotate crankshaft. Plastigage will shift,
resulting in inaccurate reading.
(6) Remove bearing cap and determine amount of
clearance by measuring width of compressed Plastigage
with scale on Plastigage envelope. Correct clearance is
0.0017 to 0.0020 inch (0.043 mm to 0.051 mm) on No. 1
through No. 4 main bearings and 0.0025 to 0.003 inch
(0.064 mm to 0.076 mm) for the rear main bearing (fig.
1B-107).
SCALE
COMPRESSED
PLASTIGAGE
4 1 9 1 7
Fig. 1 B-107 Checking lain Bearing Clearance with Plastigage
N O T E : The Plastigage should maintain the same size
across the entire width of the insert. If size varies, this
may indicate a tapered journal or dirt trapped behind
the insert.
(7) If correct clearance is indicated, bearing fitting
is not necessary. Remove Plastigage from crankshaft
and bearing. Proceed to Installation.
N O T E : Small pieces of Plastigage may remain on bear-
ing surface. They will dissolve in hot engine oil after
assembly.
(8) If oil clearance exceeds specification, install pair
of 0.001-inch undersize bearing inserts and check clear-
ance as described in steps (3) through (6).
(9) The clearance indicated with the 0.001-inch un-
dersize bearing installed will determine if the 0.001-inch
undersize inserts or some other combination will pro-
vide correct clearance. For example, if the clearance was
0.0035-inch (0.089 mm) originally, a pair of 0.001-inch
undersize inserts would reduce clearance by 0.001-inch
(0.025 mm). Oil clearance would be 0.0025 inch (0.064
mm) and within specification. A 0.002-inch undersize
insert half and a 0.001-inch undersize half would reduce
this clearance an additional 0.0005-inch (0.013 mm) and
oil clearance would be 0.002-inch (0.051 mm).
CAUTION: Never use a pair of inserts which differ
more than one bearing size as a pair. For example, do
not use a standard upper and 0.002-inch undersize lower.
(10) If oil clearance exceeds specification using 0.002-
inch undersize bearings, measure crankshaft journal
with micrometer. If journal size is correct, crankshaft
bore of cylinder block may be misaligned which requires
cylinder block replacement. If journal size is incorrect,
replace or grind crankshaft to standard undersize.
Measuring Main Bearing Journal with Micrometer (Crank-
shaft Remov el)
(1) Wipe main bearing journal clean.
(2) Measure journal diameter with micrometer.
Note difference between maximum and minimum
diameters.
(3) Refer to Specifications for maximum allowable
taper and out-of-round.
(4) Compare maximum reading obtained with jour-
nal diameters listed in Main Bearing Fitting Chart.
(5) Select inserts required to obtain specified bear-
ing clearance. Correct clearance is 0.0015 to 0.0020 inch
(0.038 mm to 0.051 mm) on No. 1 through No. 4 main
bearings and 0.0023 to 0.0027 inch (0.058 mm to 0.069
mm) for the rear main bearing.
Installation
(1) Lubricate bearing surface of each insert with
clean engine oil.
(2) Loosen all main bearing caps.
(3) Install main bearing upper insert(s).
(4) Install main bearing cap(s) and lower insert(s).
Tighten retaining screws evenly to 100 foot-pounds (136
N*m) torque in steps of 30, 60, 90 and 100 foot-pounds
(41, 81, 122 and 136 N«m) torque. Turn crankshaft at
each step to determine if crank rotates freely. If crank
does not rotate freely, check inserts for proper installa-
tion and size.
(5) After installation, turn crankshaft to check for
free operation.
(6) Install oil pan using replacement gaskets and
seals. Tighten drain plug securely.
(7) Fill crankcase to specified level with clean oil.
Bear Main Bearing Oil Seal
The rear main bearing oil seal consists of a two-piece
neoprene single lip seal. Correct installation of the seal
is required for leak-free engine operation.