engine ISUZU TROOPER 1998 Service Repair Manual

6A– 86 ENGINE MECHANICAL
Legend
(1) Piston Grade
(2) Piston Front Mark
(3) Part Number
The grade for piston outside diameter is stamped
on the piston head.
Measure the cylinder bore diameter at measuring
points.
If the piston clearance does not conform to the
specified value, the pistons most be replaced.
Piston Clearance:
0.092 – 0.110 mm (0.0036 – 0.0043 in)
Cylinder Bore Diameter mm(in)
Grade Mark Cylinder Bore Diameter
A 95.421 – 95.430 (3.7567 – 3.7571)
B 95.431 – 95.440 (3.7571 – 3.7575)
C 95.441 – 95.450 (3.7575 – 3.7579)Legend
Measuring point 1 = 20 mm
2 = 90 mm
3 = 160 mm
Piston rings
Any worn or damaged part discovered during engine
overhaul must be replaced with a new one.
1. Ring end gap measurement
1) Insert the piston ring into the cylinder bore.
2) Push the ring by the piston, at the right angle to
the wall, into the point at which the cylinder bore
diameter is the smallest.
3) Measure the ring end gap.
NOTE: The piston ring is stamped with a discerning
mark on the upper face of piston ring.
1
3
2
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ENGINE MECHANICAL 6A– 87
Discerning Mark
Piston Ring Discerning Mark
1st compression ring 1N
2nd compression ring 2N
Ring End Gap mm(in)
Piston Ring Standard Gap Limit
1st 0.25 –0.40
compression ring (0.0098 – 0.0157)
2nd 0.20 –0.35 1.5
compression ring (0.0079 – 0.0138) (0.0590)
Oil ring0.10 –0.30
(0.0039 – 0.0118)
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 and/or piston rings
must be replaced.
mm(in)
Standard Limit
1st0.05 – 0.09
Compression (0.0020 – 0.0035)
ring
2nd0.05 – 0.09 0.15
(0.0020 – 0.0035) (0.0059)
Oil ring0.03 – 0.07
(0.0012 – 0.0028)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 exceeds the
specified limit, the piston pin must be replaced.
Standard: 30.995 – 31.000 mm (1.2212 – 1.2214 in)
Limit: 30.97 mm (1.2202 in)
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6A– 88 ENGINE MECHANICAL
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: 0.008 – 0.020 mm (0.0003 – 0.0008 in )
Limit: 0.05 mm (0.0020 in)
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: 0.005 – 0.018 mm (0.0002 – 0.0007 in )
Limit: 0.04 mm (0.0016 in)
Bushing replacement
Removal: Use a suitable bar and bench press or
hammer
Installation: Align the bushing with a connecting rod
oil port. After installing a new bushing,
finish the bushing bore with a pin hole
grinder.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.
Bend per 100 mm (3.937 in)
Standard: 0.08 mm (0.0031 in) or less
Limit: 0.20 mm (0.0079 in)
Twist per 100 mm (3.937 in)
Standard: 0.05 mm (0.0020 in) or less
Limit: 0.15 mm (0.0059 in)
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: 0.230 mm (0.0091 in)
Limit: 0.350 mm (0.0138 in)
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ENGINE MECHANICAL 6A– 89
3. Measure the oil clearance between the connecting
rod and the crankshaft.
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.
1st step: 29 N·m (3.0 kg·m/22 lb ft)
2nd step: 45°– 60°NOTE: Do not allow the crankshaft to rotate
6) Remove the rod caps.
7) Measure the smallest 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
Standard: 0.022 – 0.042 mm (0.0009 – 0.0017 in)
Limit: 0.100 mm (0.0039 in)
REASSEMBLY
1. Connecting Rod
2. Piston
3. Piston Pin
1) Apply a coat of engine oil to the piston pin and
the piston pin hole.
4. Piston Pin Snap Ring
1) Try to insert the piston pin into the piston pin
hole with normal finger pressure.
2) Weight each piston and connecting rod
assembly.
3) Select piston and connecting rod combinations
so that the weight variation of the different four
assemblies is held within the specified limits.
Variance in weight after assembly: Less than 3g
(0.1058 oz)
NOTE: When changing piston/connecting rod
combinations, do not change the piston/piston pin
combination.
4) Attach the piston to the connecting rod with the
piston front mark (2) and the connecting rod
front mark (3) on the same side.
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6A– 90 ENGINE MECHANICAL
5. Piston Ring
1) Install the piston rings with the piston ring
expander.
The compression ring must be set with the 1N,
2N mark facing up.
2) Discerning mark is stamped as shown in the
illustration (1).
Marked 1N: 1st compression ring
Marked 2N: 2nd compression ring
3) Install piston rings in the following sequence.
1) Oil ring
(1) After installing the expander ring then assemble
the oil ring.
2) 2nd compression ring3) 1st compression ring
1) The compression ring must be set with the 1N or
2N mark facing up.
2) 1st compression ring:1N
3) 2nd compression ring: 2N
4) After installation, apply engine oil to the entire
circumference of the piston rings.
Check to see that all the rings rotate smoothly.
5) Insert the bearings into the connecting rods and
caps.
Apply new engine oil to the bearing faces.
Cap side bearings have no oil hole.
Connecting rod side bearing’s oil hole should be
aligned with oil hole on the connecting rod.
6. Piston and Connecting Rod
1) Apply engine oil to the cylinder bores, the
connecting rod bearings and the crankshaft
pins.
2) Check to see that the piston ring end gaps are
correctly positioned.
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ENGINE MECHANICAL 6A– 91
Legend
(1) 1st compressor ring gap
(2) 2nd compressor ring gap
(3) Oil ring gap
3) Insert the piston/connecting rod assemblies into
each cylinder with the piston ring compressor.
4) The front marks must be facing the front of the
engine.
Piston Ring Compressor : 5-8840-9018-0
7. Connecting Rod Bearing Cap
1) Apply engine oil to thread and seat of bearing
cap bolts.
2) Tighten the cap bolts in 2 steps, using angular
tightening method as shown in the following
specifications.
1st step: 29 N·m (3.0 kg·m/22 lb ft)
2nd step: 45°– 60°
After tightening the cap bolts, check to see that
the crankshaft rotates smoothly.
8. Crank Case Assembly
1) Refer to “Crank Case” in this manual.
9. Cylinder Head Assembly
1) Refer to “Cylinder head” in this manual.
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6A– 92 ENGINE MECHANICAL
CYLINDER BLOCK
1
15
14
13
8
11
16
17
10
9
72
12
3
465
18
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Legend
(1) Cylinder Head
(2) Cylinder Head Gasket
(3) Flywheel
(4) Cylinder Block Rear Plate (A/T)
Flywheel Housing (M/T)
(5) Crankshaft Rear Oil Seal
(6) Retainer
(7) Timing Gear Case Cover
(8) Crankshaft Front Oil Seal(9) Timing Gear Case
(10) Gasket
(11) Balance Shaft
(12) Crank Case
(13) Piston Cooling Oil Pipe
(14) Main Bearing Cap
(15) Crankshaft
(16) Crankshaft Timing Gear
(17) Piston and Connecting Rod Assembly
(18) Cylinder Block

ENGINE MECHANICAL 6A– 93
DISASSEMBLY
1. Cylinder Head Assembly
Refer to “Cylinder Head” in this manual.
2. Cylinder Head Gasket.
3. Flywheel
4. Cylinder Block Rear Plate (A/T), or Flywheel
housing (M/T).
5. Crankshaft Rear Oil Seal.
Install the special tool as shown in the illustration
and remove the oil seal.
Oil Seal Remover: 5-8840-2360-0
6. Retainer
7. Timing Gear Case Cover
8. Crankshaft Front Oil Seal
1) Use a plastic hammer and a screwdriver to tap
around the oil seal to free it from the gear case
cover.
9. Timing Gears
Refer to “Timing Gear” in this manual.
10. Timing gear case
11. Gasket
12. Balance shaft right
13. Crank case assembly
14. Piston cooling oil pipe
15. Piston assembly
16. Main bearing cap
17. Crankshaft assembly
18. Cylinder block side cover right and left
19. Cylinder block
INSPECTION AND REPAIR
Make the necessary adjustments, repairs, and part
replacements if excessive wear or damage is
discovered during inspection.
1. Remove the cylinder head gasket and any other
material adhering to the upper surface of the
cylinder block.
Be very careful not to allow any material to
accidentally drop into the cylinder block.
Be very careful not to scratch the cylinder block.
2. Carefully remove liquid gasket, which was used
when assembled, from gear case, rear oil seal
retainer and crank case.
3. Wipe the cylinder block clean and visually check it.
4. Use a straight edge and a feeler gauge to measure
the four sides and the two diagonals of the cylinder
block upper face.
If the measured values exceed the limit, the cylinder
block must be replaced.
Limit: 0.20 mm (0.0079 in)
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6A– 94 ENGINE MECHANICAL
Cylinder Bore Measurement
1. Use a cylinder gauge to measure the cylinder bore
measuring direction for thrust and radial at
measuring points.
Legend
Measuring Point 1; 20 mm
2; 90 mm
3; 160 mm
2. Select the right piston grade by the averaged
cylinder bore measurement (maximum and
minimum value eliminated).
Cylinder bore diameter mm(in)
Grade mark Standard
A 95.421 – 95.430 (3.7567 – 3.7571)
B 95.431 – 95.440 (3.7571 – 3.7575)
C 95.441 – 95.450 (3.7575 – 3.7579)
3. If measured values exceed the limit, replace or
adjust the cylinder block honing or boring.
Limit 95.950 mm (3.7776 in)
4. Boring of the cylinder bore is allowed until it is
0.5 mm (0.0197 in) diameter and oversized piston
is available as a service part.
Boring Cylinder Block
1. Use an oversized piston on the basis of above
mentioned cylinder using the largest inside
diameter.
2. Measure the piston outside diameter at right angles
with piston pin at a piston grade measuring point
69.75 mm (2.7461 in) from piston top surface and
calculate a inside diameter for cylinder boring.
3. Calculation of cylinder bore boring.
D + C – H (mm)
D; Outside diameter piston (mm)
C; Clearance between Cylinder bore and piston
0.092 – 0.110 mm (0.0036 – 0.0043 in)
H; Honing allowance
Less than 0.03 mm (0.0012 in)
The oversize pistons are available three grades.
4. Honing the cylinder bore after boring.
5. Measure cylinder bore after honing.
Difference between each cylinder bore
Less than 0.02 mm (0.0008 in)
Cylinder bore and piston grade (After boring) mm(in)
GradeOversize Piston Bore
Mark
Outside Diameter Diameter
A95.820 – 95.829 95.921 – 95.930
(3.7724 – 3.7728) (3.7764 – 3.7768)
B95.830 – 95.839 95.931 – 95.940
(3.7728 – 3.7732) (3.7768 – 3.7772)
C95.840 – 95.849 95.941 – 95.950
(3.7732 – 3.7736 ) (3.7772 – 3.7776)
REASSEMBLY
1. Cylinder Block
2. Piston Cooling Oil Pipe
1) Fix the cooling jet pipes with knock pins on the
cylinder block.
2) Install the oil pipe for piston cooling in the
cylinder block, tightening a relief valve (1) and
four joint bolts (2) to the specified torque.
If oil jet pipe is forcibly assembled, the end of oil
jet may bend. It could make it impossible to
supply oil to the piston cooling hole, sometimes
causing piston seizure.
Sufficient care should be taken to pipe assembly
work.
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ENGINE MECHANICAL 6A– 95
Oil pipe fixing bolts
M8: 20 N·m (2.0 kg·m/14 lb ft)
M6: 8 N·m (0.8 kg·m/69 lb in)
Relief valve fixing bolts : 30 N·m (3.1 kg·m/22 lb ft)
CAUTION: After installing the piston assembly,
check and see that there is appropriate clearance
between pistons and oil jet pipes by rotating
crankshaft slowly.
3. Crankshaft
1) Install the main bearings to the cylinder body
and the main bearing caps.
2) Be sure that they are positioned correctly.
3) Apply new engine oil to the upper and lower
main bearing faces.
4) Carefully mount the crankshaft.5) Apply engine oil to the thrust washer.
6) Assemble the thrust washer to the No. 3
bearing journal. The oil grooves must face the
crankshaft.
4. Main Bearing Cap Assembly
1) Install the bearing caps with the bearing cap
head arrow mark facing the front of the engine.
2) Apply engine oil to the crankshaft bearing cap
bolts.
3) Tighten the crankshaft bearing cap bolts to the
specified torque a little at a time in the sequence
shown in the illustration.
Torque: 167 N·m (17.0 kg·m/123 lb ft)
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