Isuzu D-Max / Isuzu Rodeo (TFR/TFS). Manual — part 566

6A – 102 ENGINE MECHANICAL

FLYWHEEL AND RING GEAR

Flywheel

1. Inspect the flywheel friction surface for excessive wear

and heat cracks.

2. Measure the flywheel friction surface depth.

If the measured value is within the specified limit, the
flywheel may be reground.
If the measured value exceeds the specified limit, the
flywheel must be replaced.

Flywheel Friction Surface Depth

Q

mm

(in)

Standard

Limit

4JA1, 4JA1T,
4JA1TC

20 (0.787)

21 (0.827)

4JB1T 14

(0.551)

15

(0.591)

4JG2T,
4JH1TC

18 (0.708)

19 (0.748)

Flywheel Friction Surface Roughness

mm (in)

Less than 0.006 (0.00024)

Ring Gear

Inspect the ring gear.
If the ring gear teeth are broken or excessively worn, the
ring gear must be replaced.

Ring Gear Replacement

Ring Gear Removal

Strike around the edges of the ring gear with a hammer
and chisel to remove it.

Ring Gear Installation

1. Heat the ring gear evenly with a gas burner to invite

thermal expansion.
Do not allow the temperature of the gas burner to
exceed 200

°C (390°F).

2. Install the ring gear when it is sufficiently heated.

The ring gear must be installed with the chamfer
facing the clutch.

ENGINE MECHANICAL 6A – 103

PISTON

Piston Grade Selection and Cylinder Bore
Measurement

Refer to the Section “CYLINDER BODY”, Item “Cylinder
Liner Bore Measurement” for details on piston grade
selection and cylinder liner bore measurement.

PISTON RING

Piston Ring Gap

1. Insert the piston ring horizontally (in the position it

would assume if it were installed to the piston) into the
cylinder liner.

2. Push the piston ring into the cylinder bore until it

reaches the measuring point

Q

or

R

where the

cylinder liner bore is the smallest.

Do not allow the piston ring to slant to one side or the
other. It must be perfectly horizontal.
Measuring Point

Q

10 mm (0.4 in)

or
Measuring Point

R

120 mm (4.7 in)

3. Use a feeler gauge to measure the piston ring gap.

If the measured value exceeds the specified limit, the
piston ring must be replaced.

Piston Ring Gap

mm (in)

Standard

Limit

1st Compression Ring

2nd Compression Ring

0.2 – 0.4

(0.008 – 0.016)

Oil Ring

0.1 – 0.3

(0.004 – 0.012)

1.5

(0.059)

4JG2

mm (in)

Standard Limit

1st

0.20 – 0.35

(0.0079 – 0.0138)

Compression
ring

2nd

0.37 – 0.52

(0.0146 – 0.0205)

Oil ring

0.20 – 0.40

(0.0079 – 0.0157)

1.5

(0.059)

6A – 104 ENGINE MECHANICAL

4JH1TC

mm (in)

Standard Limit

1st

0.30 – 0.50

(0.0118 – 0.0197)

Compression
ring

2nd

0.30 – 0.50

(0.0118 – 0.0197)

Oil ring

0.25 – 0.45

(0.0098 – 0.0117)

0.15

(0.0059)

Piston Ring and Piston Ring Groove Clearance

Use a feeler gauge to measure the clearance between the
piston ring and the piston ring groove at several points
around the piston.
If the clearance between the piston ring and the piston ring
groove exceeds the specified limit, the piston ring must be
replaced.
Piston Ring and Piston Ring Groove
Clearance
4JA1, 4JB1T, 4JA1T, 4JA1TC mm (in)

Standard

Limit

1st Compression Ring

0.09 – 0.125

(0.0035 – 0.0049)

2nd Compression Ring

0.05 – 0.085

(0.002 – 0.0033)

Oil Ring

0.03 – 0.070

(0.0012 – 0.0028)

0.15

(0.0059)

4JG2, 4JH1TC mm (in)

Standard Limit

1st

0.09 – 0.13

(0.0035 – 0.0051)

Compression
ring

2nd

0.05 – 0.09

(0.0020 – 0.0035)

Oil ring

0.03 – 0.07

(0.0012 – 0.0028)

0.15

(0.0059)

4. Visually inspect the piston rings.

If a piston ring groove is damaged or distorted, the
piston must be replaced.

015RY00029

ENGINE MECHANICAL 6A – 105

PISTON PIN

Piston Pin Diameter

Use a micrometer to measure the piston pin diameter at
several points.
If the measured value is less than the specified limit, the
piston pin must be replaced.
Piston Pin Diameter

mm (in)

Standard Limit

4JA1
4JA1T
4JA1TC
4JH1TC

30.995 – 31.000

(1.2202 – 1.2204)

30.97 (1.219)

4JB1T
4JG2T

33.994 – 34.000

(1.3383 – 1.3386)

33.97 (1.337)

Piston Pin and Piston Clearance

Use and inside dial indicator to measure the piston pin
hole (in the piston).
Piston Pin Hold

mm (in)

Standard

4JA1, 4JA1T

31.002 – 31.010 (1.2206 – 1.2208)

4JB1T
4JG2T

34.002 – 34.010 (1.3387 – 1.3390)

(1.3383 – 1.3386)

4JA1TC
4JH1TC

31.005 – 31.013 (1.2207 – 1.2210)

Piston Pin and Piston Pin Hole Clearance

mm (in)

0.002 – 0.015 (0.00008 – 0.0006)

4JA1TC, 4JH1TC

0.005 – 0.018 (0.00019 – 0.0007)

CYLINDER HEAD GASKET SELECTION

Cylinder head gasket is determined by the piston head
projection from the cylinder body upper surface, in order to
improve engine performance.
Three types of gasket are provided by the difference of
thickness. Select the adequet one out of three grades of
gasket, according to the following procedure.
Before measurement, clear off carbon from the piston
head and cylinder body surface and also clean the place
where a gasket was installed.

015RY00030