Daewoo Nubira. Manual — part 141

1D – 18

I

ENGINE COOLING

DAEWOO V–121 BL4

GENERAL DESCRIPTION

AND SYSTEM OPERATION

GENERAL DESCRIPTION

The cooling system maintains the engine temperature at
an efficient level during all engine operating conditions.
When the engine is cold, the cooling system cools the en-
gine slowly, or not at all. The slow cooling of the engine al-
lows the engine to warm up quickly.

The cooling system includes a radiator and recovery sub-
system, cooling fans, a thermostat and housing, a coolant
pump, and a coolant pump drive belt. The timing belt
drives the coolant pump.

All components must function properly in order for the
cooling system to operate. The coolant pump draws the
coolant from the radiator. The coolant then circulates
through water jackets in the engine block, the intake man-
ifold, and the cylinder head. When the coolant reaches the
operating temperature of the thermostat, the thermostat
opens. The coolant then goes back to the radiator where
it cools.

The system directs some coolant through the hoses to the
heater core. This provides for heating and defrosting. The
surge tank is connected to the radiator to recover the cool-
ant displaced by expansion from the high temperatures.
The surge tank maintains the correct coolant level.

The cooling system for this vehicle has no radiator cap or
filler neck. The coolant is added to the cooling system
through the surge tank.

RADIATOR

This vehicle has a lightweight tube–and–fin aluminum ra-
diator. Three models of radiators are available: small,
standard, and heavy duty. The three models vary only by
size (capacity). Plastic tanks are mounted on the right and
the left sides of the radiator core.

On vehicles equipped with automatic transaxles, the
transaxle fluid cooler lines run through the left radiator
tank.

A radiator drain cock is on the radiator. To drain the cooling
system, open the drain cock.

SURGE TANK

The surge tank is a transparent plastic reservoir, similar to
the windshield washer reservoir.

The surge tank is connected to the radiator by a hose and
to the engine cooling system by another hose. As the ve-
hicle is driven, the engine coolant heats and expands. The
portion of the engine coolant displaced by this expansion
flows from the radiator and the engine into the surge tank.
The air trapped in the radiator and the engine is degassed
into the surge tank.

When the engine stops, the engine coolant cools and con-
tracts. The displaced engine coolant is then drawn back
into the radiator and the engine. This keeps the radiator
filled with the coolant to the desired level at all times and
increases the cooling efficiency.

Maintain the coolant level between the MIN and the MAX
marks on the surge tank when the system is cold.

COOLANT PUMP

The belt–driven centrifugal coolant pump consists of an
impeller, a drive shaft, and a belt pulley. The coolant pump
is mounted on the front of the transverse–mounted en-
gine, and is driven by the timing belt.

The impeller is supported by a completely sealed bearing.

The coolant pump is serviced as an assembly and, there-
fore, cannot be disassembled.

THERMOSTAT

A wax pellet–type thermostat controls the flow of the en-
gine coolant through the engine cooling system. The ther-
mostat is mounted in the thermostat housing to the front
of the cylinder head.

The thermostat stops the flow of the engine coolant from
the engine to the radiator in order to provide faster warm–
up, and to regulate the coolant temperature. The thermo-
stat remains closed while the engine coolant is cold, pre-
venting circulation of the engine coolant through the
radiator. At this point, the engine coolant is allowed to cir-
culate only throughout the heater core to warm it quickly
and evenly.

As the engine warms, the thermostat opens. This allows
the engine coolant to flow through the radiator, where the
heat is dissipated through the radiator. This opening and
closing of the thermostat permits enough engine coolant
to enter the radiator to keep the engine within proper en-
gine temperature operating limits.

The wax pellet in the thermostat is hermetically sealed in
a metal case. The wax element of the thermostat expands
when it is heated and contracts when it is cooled.

As the vehicle is driven and the engine warms, the engine
coolant temperature increases. When the engine coolant
reaches a specified temperature, the wax pellet element
in the thermostat expands and exerts pressure against the
metal case, forcing the valve open. This allows the engine
coolant to flow through the engine cooling system and cool
the engine.

As the wax pellet cools, the contraction allows a spring to
close the valve.

The thermostat begins to open at 87

³

C (189

³

F) and is fully

open at 102

³

C (216

³

F). The thermostat closes at 86

³

C

(187

³

F).

ELECTRIC COOLING FAN

CAUTION : Keep hands, tools, and clothing away
from the engine cooling fans to help prevent personal
injury. This fan is electric and can turn on whether or
not the engine is running.

ENGINE COOLING 1D – 19

DAEWOO V–121 BL4

CAUTION : If a fan blade is bent or damaged in any
way, no attempt should be made to repair or reuse the
damaged part. A bent or damaged fan assembly
should always be replaced with a new one. Failure to
do so can result in personal injury.

The cooling fans are mounted behind the radiator in the
engine compartment. The electric cooling fans increase
the flow of air across the radiator fins and across the con-
denser on air conditioned (A/C) equipped vehicles. This
helps to speed cooling when the vehicle is at idle or moving
at low speeds.

The main fan size is 300 mm (11.8 inches) in diameter with
five blades to aid the air flow through the radiator and the
condenser. An electric motor attached to the radiator sup-
port drives the fan.

A/C models have two fans – the main fan and the auxiliary
fan. The auxiliary fan is 300 mm (11.8 inches) in diameter.

A/C Off or Non–A/C Model

S

The cooling fans are actuated by the powertrain
control module (PCM)/engine control module
(ECM) using a low–speed cooling fan relay and a
high–speed cooling fan relay. On A/C–equipped
vehicles, a series/parallel cooling fan relay is also
used.

S

The PCM/ECM will turn the cooling fans on at low
speed when the coolant temperature reaches 93

³

C

(199

³

F) and at high speed when the coolant tem-

perature reaches 97

³

C (207

³

F).

S

The PCM/ECM will change the cooling fans from
high speed to low speed at 94

³

C (201

³

F) and will

turn the cooling fans off at 90

³

C (194

³

F).

A/C ON

S

The PCM/ECM will turn the cooling fans on at low
speed when the A/C system is on. The PCM/ECM
will change to high speed when the coolant temper-
ature reaches 115

³

C (239

³

F) or the high side A/C

pressure reaches 1 882 kPa (273 psi).

S

The cooling fans will return to low speed when the
coolant temperature reaches 112

³

C (234

³

F) and

the high side A/C pressure reaches 1 448 kPa (210
psi).

COOLANT TEMPERATURE SENSOR

The coolant temperature sensor (CTS) uses a thermistor
to control the signal voltage to the powertrain control mod-
ule (PCM)/engine control module (ECM).

ENGINE COOLANT TEMPERATURE
SENSOR

The engine coolant temperature sensor controls the nstru-
ment panel temperature indicator. The engine coolant
temperature sensor is located on the intakemanifold near
the throttle body on an SOHC engine, and on the cylinder
head under the intake manifold on a DOHC engine.

ENGINE BLOCK HEATER

The vehicle is designed to accept an engine block heater
that helps to warm the engine and to improve starting in
cold weather. It also can help to reduce fuel consumption
while a cold engine warms up.

The engine block heater is located under the intake man-
ifold and uses an existing expansion plug for installation.

Contact your Daewoo Dealer for further information or
installation.

SECTION : 1G

ENGINE EXHAUST

TABLE OF CONTENTS

SPECIFICATIONS

1G–1

. . . . . . . . . . . . . . . . . . . . . . . . . .

FASTENER TIGHTENING SPECIFICATIONS

1G–1

.

COMPONENT LOCATOR

1G–2

. . . . . . . . . . . . . . . . . . . .

EXHAUST SYSTEM

1G–2

. . . . . . . . . . . . . . . . . . . . . . .

MAINTENANCE AND REPAIR

1G–3

. . . . . . . . . . . . . . .

ON–VEHICLE SERVICE

1G–3

. . . . . . . . . . . . . . . . . . . . .

MAIN CATALYTIC CONVERTER AND

CONNECTING PIPE

1G–3

. . . . . . . . . . . . . . . . . . . . .

AUXILIARY CATALYTIC CONVERTER

1G–5

. . . . . . .

MUFFLER – FRONT

1G–7

. . . . . . . . . . . . . . . . . . . . . . .

MUFFLER – REAR

1G–9

. . . . . . . . . . . . . . . . . . . . . . . .

GENERAL DESCRIPTION AND SYSTEM

OPERATION

1G–12

. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

EXHAUST SYSTEM

1G–12

. . . . . . . . . . . . . . . . . . . . . .

MUFFLER

1G–12

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

CATALYTIC CONVERTERS

1G–12

. . . . . . . . . . . . . . .

SPECIFICATIONS

FASTENER TIGHTENING SPECIFICATIONS

Application

N

S

m

Lb–Ft

Lb–In

Auxiliary Catalytic Converter–to–Exhaust Manifold Nuts

40

30

–

Catalytic Converter–to–Front Muffler Pipe

30

22

–

Exhaust Manifold Cover Bolts

15

11

–

Front Connecting Pipe–to–Auxiliary Catalytic Converter Nuts

40

30

–

Front Muffler Pipe–to–Catalytic Converter Nuts

30

22

–

Front Muffler Pipe–to–Rear Muffler Pipe Holding Clamp Nut

50

37

–

Post–Converter Oxygen Sensor Electrical Connector

41

30

–

1G – 2

I

ENGINE EXHAUST

DAEWOO V–121 BL4

COMPONENT LOCATOR

EXHAUST SYSTEM

1. Trim Ring (if equipped)
2. Muffler
3. Metal

Clamp

4. Front

Muffler

5. Catalytic

Converter

6. Post–Converter Heated Oxygen Sensor
7. Auxiliary Catalytic Converter