Isuzu N-Series. Service manual — part 305

00-32 SERVICE INFORMATION

Piston Ring

Connecting Rod

Piston and Piston Pin Clearance

mm (in)

0.004 — 0.017 (0.0002 — 0.0007)

0.04 (0.0016)

Clearance should be wide enough for the
piston pin to be inserted under the condition
where the piston is heated to the tempera-
ture of 80

°C to 100°C (176°F to 212°F).

When an abnormal
striking sound is
heard, replace the
piston and the pis-
ton pin.

Item

Service Standard

Service Limit

Piston
Ring Gap
(Inside the
cylinder)
mm (in)

4HF1
4HF1-2

1st Compression Ring

0.24 — 0.39 (0.0094 — 0.0153)

1.50 (0.0591)

2nd Compression Ring

0.35 — 0.50 (0.0138 — 0.0197)

1.50 (0.0591)

Oil Ring

0.02 — 0.40 (0.0008 — 0.0157)

1.50 (0.0591)

4HG1
4HG1-T

1st Compression Ring

0.24 — 0.39 (0.0094 — 0.0153)

1.50 (0.0591)

2nd Compression Ring

0.35 — 0.50 (0.0138 — 0.0197)

1.50 (0.0591)

Oil Ring

0.15 — 0.35 (0.00591 — 0.0138)

1.50 (0.0591)

4HE1-TC

1st Compression Ring

0.24 — 0.40 (0.0094 — 0.0157)

1.50 (0.0591)

2nd Compression Ring

0.30 — 0.40 (0.0118 — 0.0157)

1.50 (0.0591)

3rd Compression Ring

0.30 — 0.40 (0.0118 — 0.0157)

1.50 (0.0591)

Oil Ring

0.02 — 0.40 (0.0008 — 0.0157)

1.50 (0.0591)

Piston
Ring &
Piston
Ring
Groove
Clearance
mm (in)

4HF1
4HF1-2

1st Compression Ring

0.062 — 0.092 (0.0024 — 0.0036)

0.2 (0.0078)

2nd Compression Ring

0.04 — 0.08 (0.0015 — 0.0031)

0.15 (0.0059)

Oil Ring

0.02 — 0.06 (0.0008 — 0.0024)

0.15 (0.0059)

4HG1
4HG1-T

1st Compression Ring

0.062 — 0.092 (0.0024 — 0.0036)

0.2 (0.0078)

2nd Compression Ring

0.04 — 0.08 (0.0015 — 0.0031)

0.15 (0.0059)

Oil Ring

0.02 — 0.06 (0.0008 — 0.0024)

0.15 (0.0059)

4HE1-TC

1st Compression Ring

0.09 — 0.13 (0.0035 — 0.0051)

0.2 (0.0078)

2nd Compression Ring

0.09 — 0.13 (0.0035 — 0.0051)

0.2 (0.0078)

3rd Compression Ring

0.09 — 0.13 (0.0035 — 0.0051)

0.2 (0.0078)

Oil Ring

0.03 — 0.07 (0.0012 — 0.0028)

0.15 (0.0059)

The direction of the piston ring connecting end

Alternately at 180

°. Don’t position the

connecting end in the side pressure
direction. Place the connecting end of
the oil ring and that of the expander coil
at 180

° alternately.

Item

Service Standard

Service Limit

Connecting Rod Align-
ment

mm (in) Distortion

0.05 (0.002) or less

0.20 (0.008)

Parallelism

0.05 (0.002) or less

0.20 (0.008)

Connecting Rod Small End Bush-
ing and Piston Pin Clearance

mm (in)

0.012 — 0.027 (0.0005 — 0.0011)

0.05 (0.002)

There must be clearance enough to
rotate the piston pin while holding it
lightly with its large end fixed.

Connecting Rod Bearing Spread

mm (in)

70 (2.77) or more

Item

Service Standard

Service Limit

SERVICE INFORMATION 00-33

Connecting Rod Bearing Selection
Remarks:
The connecting rod big end inside diameter grade marks (A or B) are stamped on top of the cylinder number align
marks of the big end.
4HF1 / 4HF1-2 / 4HG1 / 4HG1-T

4HE1-TC

Flywheel

Connecting Rod Bearing and
Crankpin Clearance

mm (in)

0.036 — 0.077 (0.0014 — 0.0030)

0.10 (0.004)

The difference in weight between
the connecting rod and the piston
when assembled.

N (gr / lb)

0.2 (20 / 0.28)

Connecting Rod Big End

Crankpin

Big End
Bearing
Color
Code

Grade

Mark

(Reference)

Inside Diameter

mm (in)

(Reference)

Outside Diameter

mm (in)

A

69.985 — 69.992

(2.7553 — 2.7556)

65.902 — 65.922

(2.5946 — 2.5954)

Green

B

69.993 — 70.000

(2.7556 — 2.7559)

65.902 — 65.922

(2.5946 — 2.5954)

Yellow

Connecting Rod Big End

Crankpin

Big End
Bearing
Color
Code

Grade

Mark

(Reference)

Inside Diameter

mm (in)

(Reference)

Outside Diameter

mm (in)

A

77.985 — 77.992

(3.0702 — 3.0705)

72.902 — 72.922

(2.8702 — 2.8709)

Green

B

77.993 — 78.000

(3.0706 — 3.0709)

72.902 — 72.922

(2.8702 — 2.8709)

Yellow

Item

Service Standard

Service Limit

Flywheel Thickness

mm (in)

31.4 — 31.6 (1.236 — 1.244)

(Flywheel friction surface — crankshaft

setting face)

31.0 (1.22)

Friction Surface Run-Out

mm (in)

0.2 (0.008)

Friction Surface Roughness

mm (in)

0.006 (0.0002) or less

Ring Gear

The tooth face burr
must be cham-
fered. Replace ones
when damaged
excessively.

Item

Service Standard

Service Limit

00-34 SERVICE INFORMATION

Gear Train

Lubrication System

Item

Service Standard

Service Limit

Timing Gear Backlash Gear to Gear
(In the direction of a normal line)

mm (in)

0.10 — 0.17 (0.0039 — 0.0067)

0.30 (0.012)

Hold both the gear to be checked and
the adjoining gear stationary.

Crankshaft Gear and Crankshaft
Interference

mm (in)

0.03 — 0.093 (0.0012 — 0.0037)

Camshaft Gear and Camshaft Inter-
ference

mm (in)

0.015 — 0.023 (0.0006 — 0.0009)

Idle Gear Shaft Wear

mm (in)

29.959 — 29.980 (1.1795 — 1.1803)

29.80 (1.1732)

Idle Gear Bushing Wear

mm (in)

30.000 — 30.021 (1.1811 — 1.1819)

30.1 (1.185)

Idle Gear Bushing and Idle Gear Shaft
Clearance

mm (in)

0.020 — 0.062 (0.0008 — 0.0024)

0.2 (0.008)

Idle Gear End Play

mm (in)

0.058 — 0.115 (0.0002 — 0.005)

0.2 (0.008)

Item

Service Standard

Service Limit

Oil Pump Gear Teeth and Inner

Wall Clearance

mm (in)

0.125 — 0.220 (0.0049 — 0.0087)

0.3 (0.012)

Gear and Pump
Cover Clearance

mm (in)

0.064 — 0.109 (0.0018 — 0.0043)

0.2 (0.008)

Gear Shaft Wear

mm (in)

15.989 — 16.000 (0.6295 — 0.6299)

15.9 (0.626)

Gear Shaft and Bush-
ing Clearance

mm (in)

0.04 — 0.07 (0.0016 — 0.0028)

0.2 (0.012)

Delivery Volume

cc (cu

⋅in)/rev

16.54 (1.0)

Delivery Pressure: 392kPa (4 kg/cm

2

/ 56.9 psi)

Oil Temperature:

50

± 2°C

(122

± 3.6°F)

Oil Viscosity:

SAE 30

Relief Valve Opening Pressure

Oil Gallery

441.3 (4.5 / 64.0)

(Reference)

kPa (kg/cm

2

/ psi) Oil Pump

784.5 (8.0 / 113.8)

(Reference)

SERVICE INFORMATION 00-35

Cooling System

Item

Service Standard

Service Limit

Water Pump External appearance

Check the following:

• Cracks and damages of the pump body
• Cracks and corrosion of the impeller
• Water leak from the seal unit

When an abnormal condition is found, replace the water pump
as an assembly.

Seal Unit

Push the fan center in the radial direction while rotating it and
check the seal unit for any excessive play or abnormal sound.
When there is any abnormal condition found, replace the
water pump as an assembly.

Delivery Volume

200 or more

lit (US / UK gal) / min Water Pump Speed:

3,300 rpm

Water Temperature:

80

± 2°C

(176

± 3.6°F)

Fan Drive Belt Tension

mm (in)

8 — 12 (0.31 — 0.47) ... New belt

10 — 14 (0.39 — 0.55) ... Reuse belt

Depress the drive belt mid-portion with

a 98N (10kg / 22Ib) force

Thermostat
With Jiggle
Valve

Valve Initial Open-
ing Temperature

°C (°F)

85

± 1.5 (185 ± 2.7)

Valve Lift At 100

°C

(212

°F)

mm (in)

8 (0.31) or more

Thermostat
With-Out
Jiggle Valve

Valve Initial Open-
ing Temperature

°C (°F)

82

± 1.5 (177 — 182)

Valve Lift At 95

°C

(203

°F)

mm (in)

8 (0.31) or more

Radiator

External appearance

• Check the radiator for any corrosion, water leak, fin dam-

age, or clogging. When there is any abnormal condition
found, correct the radiator or replace it.

• When deterioration, cracking or water leak is found in the

rubber hose, replace the rubber hose.

Pressure Valve
Opening Pressure

kPa (kg/cm

2

/

psi)

103.0

± 14.7 (1.05 ± 0.15 / 14.9 ± 2.1)

Vacuum Valve
Opening Pressure

kPa (kg/cm

2

/

psi)

1.0 — 4.9 (0.01 — 0.05 / 0.14 — 0.71)

Cooling Fan

Cooling Fan Pulley
Speed

rpm

3,900

Rotate the fan by
hand, and when it
doesn’t rotate
smoothly, or when
there is oil leak from
the fan clutch,
replace the fan
clutch.

Cold Condition (Bi-
metal lower than
40

°C (104°F)

rpm

900 or lower

Hot Condition (Bi-
metal higher than
70

°C (158°F)

rpm

3,300

± 150

Pulley Ratio (Crankshaft/Fan)

175 / 151