Isuzu N-Series. Manual - part 562

GENERAL ENGINE MECHANICAL 6A-5

2. Inspect the inside of the combustion chamber, the

hot plug, and the hot plug machined faces for
cracking and other damage. 
If cracking or damage is present, the cylinder head
must be replaced.

Notice:
Be absolutely certain that there are no scratches or pro-
tuberance on the combustion chamber surfaces which
will be in contact with the hot plug after it is installed.
There flaws will prevent the hot plug from seating cor-
rectly.

Hot Plug Inspection
Inspection the hot plugs for excessive wear and other
damage. Replace the hot plugs if either of these condi-
tions are discovered.
Hot Plug Installation (4JG2 only)

1. Align the hot plug knock ball (1) with the cylinder

head groove (2) and tap it temporarily into position
with a plastic hammer.

2. Place an appropriate metal plate (3) thick over the

hot plug upper surface (4).

3. Use a press (5) to exert a pressure of 44130 —

53937N (4500 — 5500 kg/9923 — 12128 lbs.) on
the metal plate covering the hot plug upper sur-
face. This will drive the hot plug into position.

4. Lightly tap the hot plug heads to make sure that

they are firmly seated.

5. Repeat the procedure Steps 1-4 for the remaining

hot plugs.

Caution:
Do not apply pressure greater than that specified.
Damage to the cylinder head will result.

6. Use a surface grinder to grind off any hot plug sur-

face protuberances.
The hot plug surfaces must be perfectly flush with
the cylinder head.

7. After grinding, make sure that the hot plug surfaces

are completely free of protuberances. 
The hot plug surfaces must also be free of depres-
sions.

Once again, lightly tap the hot plug heads to make sure
that they are firmly seated.

N6A3060E

N6A3061E

N6A3062E

6A-6 GENERAL ENGINE MECHANICAL

Heat Shield Removal (4JG2 only)
After removing the hot plugs, use a hammer (1) and a
brass bar (2) to lightly tap the lower side of the heat
shield (3) and drive it free.

Heat Shield Installation (4JG2 only)
Install the heat shield washer and the heat shield to the
cylinder head from the nozzle holder installation hole
side.
Lightly tap the flange into place with a brass bar.
The heat shield flange side must be facing up.

Notice:
Always install a new heat shield. Never reuse the old
heat shield.

Reassembly

Cylinder Head

1. Hot plug

• Set the nock ball in the positioning groove on

the cylinder head side according to the order of
the cylinders, and hit it lightly with a plastic
hammer.

Notice:
After being pressed into the cylinder head, the hot plugs
were provided with surface grinding.
Accordingly, their dimensions are different individually
among them, and take care not confuse the order of the
cylinders.

When replacing the hot plug with new one:

When assembling a new hot plug, set the knock
ball in the positioning groove on the cylinder side
and hit it lightly with a plastic hammer until the hot
plug is set in stably.
With patch attached to the hot plug to prevent it
from being damaged, press it in with a force of 4.5
to 5.5 ton applied.
After pressing the hot plug, grind its surface to the
cylinder head.
And finally, hit the hot plug lightly with a plastic
hammer and check it for any excessive sinking,
protrusion or backlash.

N6A3063E

N6A3064E

Legend

1. Gasket
2. Nozzle heat shield
3. Colgate washer
4. Gasket heat shield
5. Nozzle

N6A3065E

GENERAL ENGINE MECHANICAL 6A-7

2. Valve Seat Insert Installation

1) Carefully place the attachment (1) (having a

smaller outside diameter than the valve seat in-
sert) on the valve seat insert (2).

Notice:
The smooth side of the attachment must contact the
valve seat insert.

2) Use the bench press (3) to gradually apply

pressure to the attachment and press the valve
seat insert into place.

Notice:
Do not apply an excessive amount of pressure with the
bench press. Damage to the valve seat will result.

Measure the height of the valve guide upper end from
the upper face of the cylinder head.

Notice:
If the valve guide has been removed, both the valve and
the valve guide must be replaced as a set.

3) Spring lower seat
4) Valve stem oil seal

• Install a new oil controller in the valve.
• Guide using special tool

Oil seal installer: 5-8840-2003-0

5) Valve

• Apply engine oil to the outside of the valve

stem before installing it.

6) Valve Spring

• Attach the valve spring to the upper spring

seat.

Valve Guide Upper End Height (H) (Reference)

mm (in)

13 (0.51)

N6A3086E

N6A3067E

N6A3068E

6A-8 GENERAL ENGINE MECHANICAL

Caution:

• The painted area of the valve spring should be fac-

ing downward.

• Apply compressed air to cylinder from the

glow plug hole to hold the valve in place.

• Install split collar by special tool.

Valve spring compressor: 9-8523-1423-0 (J-
29760)

7) Split Collar

• Use a spring compressor to push the valve

spring into position.

• Install the spring seat split collar.
• Set the split collar by tapping lightly around

the head of the collar with a rubber hammer.

Valve spring compressor: 9-8523-1423-0 (J-
29760)

3. Push Rod
4. Rocker Arm Shaft and Rocker Arm

Tighten:

• Rocker arm shaft fixing bolts to 54 N

⋅m (5.5 kg⋅m/40

lb

⋅ft)

5. Glow Plug and Glow Plug Connector 

(4JB1/4JB1-TC/4JH1-TC)

Tighten:
Glow plugs to 23 N

⋅m (2.3 kg⋅m/17 lb⋅ft)

6. Injection Nozzle Holder (4JB1/4JB1-TC only)
7. Injection Nozzle Holder (4JH1-TC only)

1) Install the injection nozzle gasket (1) and the O-

ring (2) to the injection nozzle holder (3).
Be sure that the O-ring fits snugly in the injec-
tion nozzle groove.

2) Apply engine oil to the cylinder head nozzle

holder hole.

3) Install the nozzle holder together with the noz-

zle holder bracket (4) to the cylinder head.

Tighten:
37 N

⋅m (3.8 kg⋅m/27 lb⋅ft)

8. Injection Nozzle (4JG2 only)

• Lightly tighten the holder nut to suck extent that

the nozzle holder can turn one word and one
word.

• Set positioning confirmation drilled hole (

φ2)

within a nozzle turning angle of 

±5° against the

cylinder head side positioning boss.

N6A3069E

N6A3070E

N6A3071E