ISUZU TROOPER 1998 Service Repair Manual

ENGINE MECHANICAL 6A Ð 31
·Install the bearing caps with the bearing cap head
arrow mark facing the front of the engine.
·Apply engine oil to the crankshaft bearing cap bolts.
·Tighten the crankshaft bearing cap bolts to the
specified torque a little at a time in the sequence
shown in the illustration.
NOTE:
Check to see that the crankshaft turns smoothly by rotating
it manually.
12. Piston and Connecting Rod Assembly
·Apply engine oil to the cylinder bores, the connect-
ing rod bearings and the crankshaft pins and each
piston ring and piston.
Check to see that the piston ring end gaps are
correctly positioned.
29 (3.0/22)
N·m(kg·m/lb.ft) Oiling Jet Plug
10. Oil Pump Assembly
1) Prepare a solution of 80% engine oil and 20%
molybdenum disulfide.
2) Apply an ample coat of the solution to the teeth of
the oil pump pinion.
3) Install the oil pump and tighten the bolts to the
specified torque.After tightening the cap nuts, check to see that the
crankshaft rotates smoothly.
11. Piston Cooling Oil Pipe
·Tighten the bolt and oiling jet plug to the specified
torque ·Insert the piston/connecting rod assemblies into
each cylinder with the piston ring compressor.
Piston ring compressor: 5-8840-9018-0
The front marks must be facing the front of the
engine.
·Match the numbered caps with the numbers on the
connecting rods. Align the punched marks on the
connecting rods and caps.
·Apply engine oil to the threads and seating faces of
the nuts.
·Tighten the cap nuts in 2 steps, using angular tight-
ening method as shown in the following specifica-
tions.
167 (17.0/123)N·m(kg·m/lb·ft)
N·m (kg·m/lb·ft)
45¡ ~ 60¡ 1st step 2nd step
29 (3.0/22)
N·m (kg·m/lb·ft)
19 (1.9/14) M6 8 (0.8/6)
M8

6A Ð 32 ENGINE MECHANICAL
19 (1.9/14)N·m(kg·m/lb·ft)
5. Timing Gear Case
1) Install the timing gear case to the cylinder body.
NOTE:
Take care not to twist the front oil seal.
6. Flywheel
1) Thoroughly clean and remove the oil from the
threads of crankshaft.
2) Mount the flywheel on the crankshaft and then
install the washer.
3) Align the flywheel with the crankshaft dowel pin.
4) Tighten the flywheel bolts to the specified torque
in the numerical order shown in the illustration.
82 (8.4/61)N·m(kg·m/lb·ft)
NOTE:
Take care not to damage the O-rings when tightening the
oil pipe bolts.
9. Crankcase Assembly
·Refer to ÒCrankcaseÓ Section 6A2
8. Crankshaft Rear Oil Seal
1) Tighten the adapter to the crankshaft rear and
section with 2 bolts.
2) Insert the oil seal into the peripheral section of the
adapter,
3) Insert the sleeve into the adapter section, and 1)
tighten it with a bolt (M12 x 1.75L = 70) until the
adapter section hits the sleeve.
4) Remove the adapter and the sleeve.
5) With the seal pressed in, check the dimension of
the oil seal section.
Standard Dimension = 12.5 ± 0.3 mm
Oil Seal Installer: 5-8840-2359-0
7. Cylinder Block Rear Plate
Align the rear plate with the cylinder body knock pins.
Tighten the rear plate to the specified torque.
118 (12.0/87)N·m(kg·m/lb·ft)

ENGINE MECHANICAL 6A Ð 33
2) Tighten the timing gear case bolt together with
the timing gear case gasket to the specified
torque.
19 (1.9/14)N·m(kg·m/lb·ft)
3) Cut away the gasket protruding above the fitting
surfaces (as shown in the illustration).
4. Crankshaft Front Oil Seal
·Use the installer to install the front oil seal 1 to
the gear case cover 2.
Oil Seal Installer: 5-8840-2061-0
Note the oil seal installation depth 3 shown in
the illustration.
Depth 3 = 1 mm (0.0394 in.)
3. Crankshaft Timing Gear
Use the crankshaft timing gear installer 1 to install the
timing gear 2.
The crankshaft timing mark (ÒX Ð XÓ) must be facing
outward.
Crankshaft Timing Gear Installer: 5-8522-0024-0
2. Camshaft Timing Gear
·Tighten the fixing bolt to the specified torque.
64 (6.5/47)N·m(kg·m/lb·ft)
1. Cylinder Head
·Refer to ÒCylinder headÓ in Section 6A2.

6A Ð 34 ENGINE MECHANICAL
PISTON AND CONNECTING ROD
DISASSEMBLY
1. Cylinder Head Assembly
·Refer to ÒCylinder headÓ in Section 6A2.
2. Crankcase Assembly
·Refer to ÒCrankcaseÓ in Section 6A2
3. Oil Pump Assembly
4. Connecting Rod Bearing Cap
5. Piston and Connecting Rod
·Remove carbon deposits from the upper portion
of the cylinder wall with a scraper before
removing the piston and connecting rod

ENGINE MECHANICAL 6A Ð 35
6. Piston Ring
Remove the piston rings with a piston ring expander.
Arrange the removed piston rings in the cylinder
number order.
7. Piston Pin Snap Ring
·Use a pair of pliers to remove the piston pin snap
rings
8. Piston Pin
NOTE:
Keep the parts removed from each cylinder separate. All
parts must be reinstalled in their original positions.
9. Piston
10. Connecting Rod
INSPECTION AND REPAIR
PISTON AND PISTON RING
Pistons
Carefully clean away all the carbon adhering to the piston
head and the piston ring grooves.
NOTE:
Never use a wire brush to clean the pistons. Damage will
result.
Visually check each piston for cracking, scoring, and other
signs of excessive wear.
If any of the above conditions are present, the piston
must be replaced.
Piston Diameter
1. Measure the piston outside diameter with micrometer
at the piston grading position.
71.00 (2.7974)
mm(in) Piston Grading Position

6A Ð 36 ENGINE MECHANICAL
Piston rings
Any worn or damaged part discovered during engine
overhaul must replaced with a new one.
1. Ring end gap measurement
·Insert the piston ring into the bore. Grade Mark Piston Outside Diameter
Following are installed piston grade from factory.
Outside Diameter
Factory
GradeService Part
GradeOutside Diameter A
B
C
D95.365 – 95.374 (3.7545 – 3.7549)
95.375 – 95.384 (3.7549 – 3.7553)
95.385 – 95.394 (3.7553 – 3.7557)
95.395 – 95.404 (3.7557 – 3.7561)
95.369 – 95.384
(3.7547 – 3.7553)
95.385 – 95.400
(3.7553 – 3.7559) A and B
C and DAX
CX
mm (in)
Method of selection grade for piston service part.mm (in)
Grade Mark Inside Diameter
A
B
C
D95.425 – 95.440 (3.7569 – 3.7575)
95.441 – 95.450 (3.7575 – 3.7579)
95.451 – 95.460 (3.7579 – 3.7583)
95.461 – 95.475 (3.7583 – 3.7589)
Cylinder Liner Bore Diameter
Following are installed cylinder liner bore grade from factory.
Factory
GradeService Part
GradeOutside Diameter
95.435 – 95.450
(3.7573 – 3.7579)
95.451 – 95.466
(3.7579 – 3.7585) A and B
C and DAX
CXmm (in)
Method of selection grade for cylinder liner service part.
mm (in)
The grading position for piston outside diameter is
represented by the Grade mark as shown in Figure.
Measure the cylinder bore inside diameter (refer to
ÒInspection of the Cylinder BlockÓ in this Section).
If the piston clearance does not conform to the specified
valve, the pistons and/or cylinder liners most be replaced.
0.051 – 0.066 (0.0020 – 0.0026)
mm(in) Piston Clearance

ENGINE MECHANICAL 6A Ð 37
·Push the ring by the piston, at a right angle to the
wall, into the point at which the cylinder bore
diameter is the smallest.
·Measure the ring end gap.
Standard
Compression
ringLimit
1st/2nd0.20-0.35
(0.0079-0.0138)
1.5
(0.0591)
0.10-0.30
(0.0039-0.0118) Oil ringmm(in)
2. Measure the clearance between the piston ring groove
and the piston ring with a feeler gauge. If the piston ring
groove/piston ring clearance exceeds the specified limit,
the piston must be replaced.
Standard
Compression
ringLimit
Top 0.05-0.09
(0.0020-0.0035)
2nd 0.05-0.09
(0.0020-0.0035)
0.15
(0.0059)
0.03-0.07
(0.0012-0.0028) Oil ringmm(in)
Piston pin
Visually inspect the piston pin for cracks, flaws, and other
damage and replace if necessary.
1. Use a micrometer to measure the piston pin outside
diameter in both directions at three different
positions. If the measurement exceed the specified
limit, the piston pin must be replaced.
Standard
Piston pin outside
diameterLimit
33.995-34.000
(1.3384-1.3386)
33.970
(1.3374)
mm (in)
2. Measure the inside diameter of the connecting rod
small end. If the clearance between the small end
and pin does not conform to the specified value, the
connecting rod or bushing and pin must be replaced.
Standard
Limit
0.008 ~ 0.020
(0.0003 ~ 0.0008)0.05
(0.0020)
Clearancemm (in)

6A Ð 38 ENGINE MECHANICAL
NOTE:
Align the bushing with the connecting rod oil port.
After installing a new bushing, finish the bushing bore
with a pin hole grinder. 3. Insert the piston pin into the piston and rotate it. If
the pin rotates smoothly with no backlash, the
clearance is normal. If there is backlash or
roughness, measure the clearance. If the clearance
exceeds the specified limit, the piston and the piston
pin must be replaced.
Standard Limit
0.002 ~ 0.015
(0.00008 ~ 0.0006)0.04
(0.0016) Clearancemm (in)
Bushing replacement
Removal: Use a suitable bar and bench press or
hammer.
Installation: Use a suitable bar and bench press.
Connecting rods
1. Check the connecting rod alignment with a
connecting rod aligner.
If either the bend or the twist exceeds the specified
limit, the connecting rod must be replaced.
2. Measure the connecting rod thrust clearance.
Use a feeler gauge to measure the thrust clearance at
the big end of the connecting rod.
If the clearance exceeds the specified limit, the
connecting rod must be replaced.
Standard Limit
0.230 (0.0091) 0.350 (0.0138)mm (in)
Limit
Bend per 100 (3.937)
Twist per 100 (3.937)mm (in)
0.20 (0.0079)
0.15 (0.0059)Standard
0.08 (0.0031) or less
0.05 (0.0020) or less

ENGINE MECHANICAL 6A Ð 39
3. Measure the oil clearance between the connecting
rod and the crankshaft by:
1) Remove the connecting rod cap nuts and the rod
caps.
Arrange the removed rod caps in the cylinder
number order.
2) Clean the rod bearings and the crankshaft pins.
3) Carefully check the rod bearings.
If even one bearing is found to be damaged or
badly worn, the entire bearing assembly must be
replaced as a set. Reinstall the bearings in their
original positions.
Apply plastigage to the crank pin.
4) Reinstall the rod caps to their original positions.
5) Tighten the cap nuts in 2 steps, using angular
tightening method as shown in the following
specifications.
NOTE:
Do not allow the crankshaft to rotate.
N·m (kg·m/lb·ft)
45¡ ~ 60¡ 1st step 2nd step
29 (3.0/22)
6) Remove the rod caps.
7) Measure the width of the plastigage and determine
the oil clearance. If the oil clearance exceeds the
limit, replace the rod bearings as a set.
8) Clean the plastigage from the bearings and the
crankshaft pins.
REASSEMBLY
10. Connecting Rod
9. Piston
8. Piston Pin
·Apply a coat of engine oil to the piston pin and the
piston pin hole.
7. Piston Pin Snap Ring
·Apply a thin coat of engine oil to the piston pin.
Try to insert the piston pin into the piston pin hole
with normal finger pressure.
Weigh each piston and connecting rod assembly.
Select piston and connecting rod combinations so
that the weight variation of the different assemblies
is held within the specified limits.
Variance in weight
after assemblyLess than 3
(0.1058)g (oz)
Standard Limit
0.029 (0.0011) – 0.083 (0.0033) 0.100 (0.0039)
mm (in)
NOTE:
When changing piston/connecting rod combinations, do
not change the piston/piston pin combination.

6A Ð 40 ENGINE MECHANICAL
6. Piston Ring
·Install the piston rings with the piston ring expander.
The compression ring must be set with the 1N, 2N
mark facing up.
·Discrimination mark is painted as shown in the
illustration. ·Attach the piston to the connecting rod with the
piston front mark and the connecting rod ISUZU
mark on the same side.
·Install piston rings in the following sequence.
1) Oil ring
1Expander ring
2) 2nd compression ring
3) 1st compression ring
·The compression ring must be set with the 1N or
2N mark facing up.
·1st compression ring: N
·2nd compression ring: 2N
·After installation, apply engine oil to the entire
circumference of the piston rings.
Check to see that all the rings rotate smoothly.
·Insert the bearings into the connecting rods and
caps.
Apply new engine oil to the bearing faces.
Cap side bearings have no oil hole.
Conn rod side bearingÕs oil hole should be aligned
with oil hole on the conn rod.