Isuzu N-Series. Manual - part 518

Cooling System   6B-3

Water Pump
The water pump, which uses the centrifugal impeller
system, is driven by the engine fan belt.

Legend

1. Fan Center
2. Fan Pulley
3. Bearing

4. Seal Unit
5. Impeller
6. Groove 

 

N6A6327E

6B-4   Cooling System

Thermostat
The thermostat is a wax pellet type and consists of two
units, in which one unit (bottom bypass type) has an
valve initial opening temperature of 82

°C (180 °F) and

the second (inline type) has an valve initial opening
temperature of 85

°C (185 °F). It is designed such that

the water temperature can be adjusted finely and it is
mounted within the thermostat-housing unit.

Legend

1. Jiggle Valve
2. Stamp Mark (Valve Initial Opening Temperature)
3. Valve

4. Gasket
5. Piston

 

N6A6328E

Cooling System   6B-5

Radiator
The radiator is a tube with corrugated fins. To increase
the boiling point of the cooling water, a radiator cap of
injection valve opening pressure of 108 

± 14.7 kPa (1.1

± 0.15 kg/cm

2

 / 15.7 

± 2.1 psi) is attached.

Functional Check

1. Cooling water level check

• Check the cooling water level within the reserve

tank and the level is appropriate when the
cooling water level is within the MAX (upper
limit) and MIN (lower limit) range. In case the
volume of the cooling water is deficient, remove
the reserve tank cap and replenish with a
mixture of tap water and engine coolant in the
ratio of 1:1 until the level comes close to the
MAX line.

Legend

1. Reserve Tank
2. MAX Line (Upper Limit)
3. MIN Line (Lower Limit)

 

Inspection
Cooling water leak check

• Use the radiator cap tester and apply a pressure of

196 kPa (2.0 kg/cm

2

 / 28.4 psi) and check for leaks

in the locations given below. Check that the
radiator hose and heater hose are not damaged or
degraded and the hose clamp is not loose.

Inspection locations

• Radiator assembly, water pump assembly, radiator

hose, and heater hose.

Coolant

1. About the engine coolant concentration

Standard value
Cooling water level

17.6 liters (4.65 US gal. / 3.87
Imp gal.)
(between MIN and MAX level)

Replacement period

Every two years or 40,000
kilometers (24,000 miles)

N6A6329E

N6A6330E

N6A6331E

6B-6   Cooling System

• Take the concentration corresponding to the

minimum temperature because the freezing
temperature varies according to the
concentration of the engine coolant.

• Use only genuine Isuzu engine coolant.
• Use engine coolant with a mix ratio in the range

of 30 to 60% because over heating is likely to
occur if the ratio is greater than 60% and
corrosion prevention is inadequate if the ratio is
less than 30%.

2. Engine coolant density measurement

Methods for measuring specific gravity

• Measure the specific gravity and the

temperature of the cooling water using an anti-
freeze specific gravity meter and thermometer.

Take precautionary measures as the boiled
cooling water may gush out at high
temperatures if the cap is removed.

• Use a deep container to suit the height of the

specific gravity meter.

Legend

1. Radiator
2. Anti-Freeze Specific Gravity Meter

 

• Fix the temperature of the cooling water being

measured in the range of 0 to 50

°C (32  to

122

°F).

• Measure the temperature and specific gravity

and determine the concentration from the table
given below.

Freezing

temperature

guideline

Mix ratio

Liter (qts)

Concentration

of engine 

coolant

Engine 

coolant

Tap 

water

-18

°C (-0.4°F) 4.2 (4.4) 7.8 (8.2)

35%

-25

°C (-13°F) 5.0 (5.3) 7.0 (7.4)

42%

-35

°C (-31°F) 6.0 (6.3) 6.0 (6.3)

50%

-40

°C (-40°F) 6.4 (6.8) 5.6 (5.9)

53%

N6A6332E

N6A6333E

N6A6334E