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Isuzu N-Series. Service manual - part 604

6B-2 ENGINE COOLING

GENERAL DESCRIPTION

Component

Coolant Flow

Legend

1. Radiator cap

7. Thermostat

2. Reservoir tank

8. Water pump

3. Air bleeding plug

9. Car heater

4. Cylinder head

10. Oil cooler

5. Radiator

11. C.S.D

6. Cooling fan

12. Injection pump

N6A3370E

ENGINE COOLING 6B-3

Coolant Flow (4JH1-TC)

The cooling system is a pressurized coolant forced cir-
culation type which consists of water pump, thermostat
cooling fan, radiator and other components. The circu-
lating coolant cools the lubricating oil in the oil filter and
turbocharger.

Water Pump

The coolant pump is a centrifugal impeller type and is
driven by V type drive belt.
The water pump is not disassembled type.

Legend

1. Radiator cap

7. Thermostat

2. Reservoir tank

8. Water pump

3. Air bleeding plug

9. Car heater

4. Cylinder head

10. Oil cooler

5. Radiator

11. Turbo charger

6. Cooling fan

12. EGR Cooler

N6A3371E

N6A3372E

6B-4 ENGINE COOLING

Thermostat

The thermostat is a wax pellet type with a juggle valve
and is installed in the thermostat housing.

Radiator

The radiator is a tube type with corrugated fins. In order
to raise the boiling point of coolant, the radiator is adjust-
ed through a valve fitted to the upper tank to a pressure
range of 93 — 123 kPa (0.95 — 1.25 kg/cm

). The cap

fitted to the cylinder head thermostat housing has only a
water supply function.

The 4JH1-TC engine is equipped with the intercooler.

Engine Coolant Change Procedure

1. To change engine coolant, make sure that the en-

gine is cool.

Warning:

WARNING:
WHEN THE COOLANT IS HEATED TO A HIGH TEM-
PERATURE, BE SURE NOT TO LOOSEN OR RE-
MOVE THE RADIATOR CAP.
OTHERWISE YOU MIGHT GET SCALDED BY HOT
VAPOR OR BOILING WATER. TO OPEN THE RADI-
ATOR CAP, PUT A PIECE OF THICK CLOTH ON THE
CAP AND LOOSEN THE CAP SLOWLY TO REDUCE
THE PRESSURE WHEN THE COOLANT HAS BE-
COME COOLER.

2. Open radiator cap and drain the cooling system by

loosening the drain valve on the radiator and on the
cylinder body.

Notice:
For best result it is suggested that the engine cooling
system be flushed at least once a year. It is advisable to
flush the interior of the cooling system including the ra-
diator before using specified coolant.
Replace damaged rubber hoses as the engine specified
coolant. Coolant is liable to leak out even minor cracks.
Isuzu recommends to use Isuzu genuine specified cool-
ant or equivalent, for the cooling system and not add any
inhibitors or additives.

Caution:
A failure to correctly fill the engine cooling system in
changing or topping up coolant may sometimes cause
the coolant to overflow from the filler neck even before
the engine and radiator are completely full.

Legend

1. Jiggle valve

N6A3373E

N6A3374E

Legend

1. Radiator
2. Charge air cooler

N6A3375E

ENGINE COOLING 6B-5

If the engine runs under this condition, shortage of cool-
ant may possibly result in engine overheating. To avoid
such trouble, the following precautions should be taken
in filling the system.

3. To refill engine coolant, pour coolant up to filler

neck using a filling hose which is smaller in outside
diameter of the filler neck.
Otherwise air between the filler neck and the filling
hose will block entry, preventing the system from
completely filling up.

4. Keep a filling rate of 9 liter/min. or less. Filling over

this maximum rate may force air inside the engine
and radiator.
And also, the coolant overflow will increase, mak-
ing it difficult to determine, whether or not the sys-
tem is completely full.

5. After filling the system to the full, pull out the filling

hose and check to see if air trapped in the system
is dislodged and the coolant level goes down.
Should the coolant level go down, repeat topping-
up until there is no more drop in the coolant level.

6. After directly filling the radiator, fill the reservoir to

the maximum level.

7. Install and tighten radiator cap and start the en-

gine. After idling for 2 to 3 minutes, stop the engine
and reopen radiator cap. If the water level is lower,
replenish.

Warning:

8. After tightening radiator cap, warm up the engine at

about 2,000 rpm.
Set heater adjustment to the highest temperature
position, and let the coolant circulate also into heat-
er water system.

9. Check to see the thermostat has opened through

the needle position of water thermometer, conduct
a 5 minutes idling again and stop the engine.

10. When the engine has been cooled, check filler

neck for water level and replenish if required.
Should extreme shortage of coolant is found,
check the coolant system and reservoir tank hose
for leakage.

11. Fill the coolant into the reservoir tank up to “MAX”

line.

Specified Coolant Solution

• Relation between Mixing ratio and Freezing point

Freezing temperature of the engine coolant varies
with the ratio of specified coolant solution in water.

Proper mixing ratio can be determined by referring
to the chart. Supplemental inhibitors or additives
claiming to increase cooling capability that have
not been specifically approved by Isuzu are not
recommended for addition to the cooling system.

• Calculation of mixing ratio

Notice:
Specified coolant solution + Water = 10 lit
Total cooling system capacity.
In case of 6.8 lit total cooling system capacity

Legend

A. Mixing ratio
B. Freezing point

Mixing ratio

Specified coolant solution (Lit/qt.)

Specified coolant solution (Lit/qt.) + Water (Lit/

qt.)

Mixing

ratio (%)

Specified coolant

solution:

lit. (imp. qt./U.S. qt)

Water:

lit. (imp. qt/U.S. qt)

(8.80/10.57)

0.5

(0.44/0.53)

9.5

(8.36/10.04)

1.0

(0.88/1.06)

9.0

(7.92/9.51)

1.5

(1.32/1.59)

8.5

(7.48/8.98)

2.0

(1.76/2.11)

8.0

(7.04/8.45)

2.5

(2.20/2.64)

7.5

(6.60/7.93)

3.0

(2.64/3.17)

7.0

(6.16/7.40)

3.5

(3.08/3.70)

6.5

(5.72/6.87)

4.0

(3.52/4.23)

6.0

(5.28/6.34)

4.5

(3.96/4.76)

5.5

(4.84/5.81)

N6A3376E

Content .. 602 603 604 605 ..