Isuzu Trooper (1998-2002 year). Service manual - part 569

6A – 84 ENGINE MECHANICAL

PISTON AND CONNECTING ROD

5

8

7

3

1

2

6

4

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Legend

(1)

Cylinder Head Assembly

(2)

Crank Case

(3)

Connecting Rod Bearing Cap

(4)

Connecting Rod

(5)

Piston Ring

(6)

Piston Pin

(7)

Piston Pin Snap Ring

(8)

Piston

ENGINE MECHANICAL 6A – 85

DISASSEMBLY

1. Cylinder Head Assembly

1) Refer to “Cylinder head” in this manual.

2. Crank Case Assembly

1) Refer to “Crank Case” in this manual.

3. Connecting Rod Bearing Cap
4. Piston and Connecting Rod

1) Remove carbon deposits from the upper portion

of the cylinder wall with a scraper before
removing the piston and connecting rod.

5. Piston Ring

Remove the piston rings with a piston ring
expander.
Arrange the removed piston rings in the cylinder
number order.

6. Piston Pin Snap Ring

1) Use a pair of pliers to remove the piston pin

snap rings.

7. Piston Pin

1) Remove piston pin from piston assembly.

NOTE: Keep the parts removed from each cylinder
separate. All parts must be reinstalled in their original
positions.

8. Piston
9. 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.

Piston Grading Position:  69.75 mm (2.7461 in)
from piston head

Piston Outside Diameter

mm(in)

Grade Mark

Outside Diameter

A

95.320 – 95.329 (3.7527 – 3.7531)

B

95.330 – 95.339 (3.7531 – 3.7535)

C

95.340 – 95.349 (3.7535 – 3.7539)

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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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3

2

1

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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 ring

0.10 – 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

1st

0.05 – 0.09

Compression

(0.0020 – 0.0035)

ring

2nd

0.05 – 0.09

0.15

(0.0020 – 0.0035)

(0.0059)

Oil ring

0.03 – 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)

N

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