Nissan Xterra. Manual — part 173

COOLING SYSTEM

CO-7

< SYSTEM DESCRIPTION >

[VQ40DE]

C

D

E

F

G

H

I

J

K

L

M

A

CO

N

P

O

Schematic

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WBIA0565E

CO-8

< SYSTEM DESCRIPTION >

[VQ40DE]

OVERHEATING CAUSE ANALYSIS

OVERHEATING CAUSE ANALYSIS

Troubleshooting Chart

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Symptom

Check items

Cooling sys-
tem parts
malfunction

Poor heat transfer

Water pump malfunction

Worn or loose drive belt

—

Coolant circulation

Thermostat stuck closed

Damaged fins

Dust contamination or pa-
per clogging

Physical damage

Clogged radiator cooling
tube

Excess foreign material
(rust, dirt, sand, etc.)

Reduced air flow

Cooling fan does not oper-
ate

Fan assembly

—

High resistance to fan rota-
tion

Damaged fan blades

Damaged radiator shroud

—

Radiator shroud

—

Improper engine coolant
mixture ratio

—

Engine coolant viscosity

—

Poor engine coolant quality

—

—

Insufficient engine coolant

Engine coolant leaks

Cooling hose

Loose clamp

Cracked hose

Heater pump

Physical damage

Water pump

Poor sealing

Radiator or reservoir cap

Loose

Poor sealing

Radiator

O-ring for damage, deterio-
ration or improper fitting

Cracked radiator tank

Cracked radiator core

Reservoir tank

Cracked reservoir tank

Overflowing reservoir tank

Exhaust gas leaks into cool-
ing system

Cylinder head deterioration

Cylinder head gasket deteri-
oration

OVERHEATING CAUSE ANALYSIS

CO-9

< SYSTEM DESCRIPTION >

[VQ40DE]

C

D

E

F

G

H

I

J

K

L

M

A

CO

N

P

O

Except cool-
ing system
parts mal-
function

—

Overload on engine

Abusive driving

High engine rpm under no
load

Driving in low gear for ex-
tended time

Driving at extremely high
speed

Powertrain system malfunc-
tion

—

Installed improper size
wheels and tires

Dragging brakes

Improper ignition timing

Blocked or restricted air
flow

Blocked bumper

Installed car brassiere

—

Blocked radiator grille

Installed car brassiere

Mud contamination or paper
clogging

Blocked radiator

Blocked air flow

Blocked condenser

Installed large fog lamp

Symptom

Check items

CO-10

< PERIODIC MAINTENANCE >

[VQ40DE]

ENGINE COOLANT

PERIODIC MAINTENANCE

ENGINE COOLANT

System Inspection

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WARNING:

Do not remove the radiator/reservoir cap when the engine is hot. Serious burns could occur from high

pressure fluid escaping from the radiator or reservoir. Wrap a thick cloth around the cap. Slowly push

down and turn it a quarter turn to allow built-up pressure to escape. Carefully remove the cap by push-

ing down and turning it all the way.

CHECKING COOLING SYSTEM HOSES

Check hoses for the following:

• Improper attachment

• Leaks

• Cracks

• Damage

• Loose connections

• Chafing

• Deterioration

CHECKING RESERVOIR LEVEL

• Check if the engine coolant reservoir tank level is within MIN to

MAX when the engine is cool.

• Adjust engine coolant level as necessary.

CHECKING COOLING SYSTEM FOR LEAKS

WARNING:

Do not remove the radiator/reservoir cap when the engine is hot. Serious burns could occur from high

pressure coolant escaping from the radiator or reservoir.

To check for leakage, apply pressure to the cooling system at the

reservoir filler neck using suitable tool and Tool.

CAUTION:

Higher pressure than specified may cause radiator damage.

NOTE:

In case that engine coolant decreases, replenish cooling system with

engine coolant.

If any concerns are found, repair or replace damaged parts.

CHECKING RESERVOIR CAP

1. Inspect the reservoir cap.

• Replace the cap if the metal plunger cannot be seen around the edge of the black rubber gasket.

• Replace the cap if deposits of waxy residue or other foreign material are on the black rubber gasket or

the metal retainer.

NOTE:

Thoroughly wipe out the reservoir filler neck to remove any waxy residue or foreign material.

SMA412B

Tool number

: EG17650301 (J-33984-A)

Testing pressure : Refer to

CO-30, "Standard

and Limit"

.

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