2004 DAEWOO LACETTI Iat

ENGINE COOLING 1D – 9
DAEWOO V–121 BL4
THERMOSTAT (1.4L/1.6L DOHC)
Removal Procedure
CAUTION : To prevent personal injury, do not remove
the surge tank cap while the engine and the radiator
are hot because the heat causes the system to remain
under pressure. Scalding fluid and steam may be
blown out under pressure.
1. Drain the coolant. Refer to ”Draining and Refilling
the Cooling System” in this section.
2. Loosen the hose clamp on the upper radiator hose
at the thermostat housing.
3. Disconnect the upper radiator hose from the ther-
mostat housing.
4. Loosen the clamp on the bypass hose.
5. Disconnect the bypass hose from the thermostat
housing.
6. Remove the mounting bolts that hold the thermo-
stat housing to the cylinder head.
7. Remove the thermostat housing from the head.
8. Remove the O–ring seal from the head.
9. Check the valve seat for foreign matter that could
prevent the valve from seating properly.
10. Check the thermostat for proper operation. Refer to
”Thermostat Test” in this section.
11. Clean the thermostat housing and the cylinder head
mating surfaces.
Installation Procedure
1. Coat the sealing surface of a new O–ring seal with
Lubriplater®.
2. Install a new O–ring seal into the recess in the cyl-
inder head.
3. Secure the thermostat housing to the cylinder head
with the mounting bolts.
Tighten
Tighten the thermostat housing mounting bolts to 20
NSm (15 lb–ft).

1D – 10IENGINE COOLING
DAEWOO V–121 BL4
4. Connect the upper radiator hose to the thermostat
housing.
5. Secure the upper radiator hose to the thermostat
housing with a hose clamp.
6. Connect the bypass hose to the thermostat hous-
ing.
7. Secure the bypass hose with a hose clamp.
8. Refill the engine cooling system. Refer to ”Draining
and Refilling the Cooling System” in this section.
THERMOSTAT (1.8L DOHC)
Removal Procedure
CAUTION : To prevent personal injury, do not remove
the surge tank cap while the engine and the radiator
are hot because the heat causes the system to remain
under pressure. Scalding fluid and steam may be
blown out under pressure.
1. Drain the coolant. Refer to ”Draining and Refilling
the Cooling System” in this section.
2. Loosen the hose clamp on the upper radiator hose
at the thermostat housing.
3. Disconnect the upper radiator hose from the ther-
mostat housing.
4. Remove the mounting bolts that hold the thermo-
stat housing to the cylinder head.
5. Remove the thermostat housing from the cylinder
head.
6. Remove the seal ring from the thermostat housing.
7. Remove the thermostat from the thermostat hous-
ing by pressing the thermostat mounting flange
downward and then rotating the flange clockwise.
8. Inspect the valve seat for foreign matter that could
prevent the valve from sealing properly.
9. Inspect the thermostat for proper operation. Refer
to ”Thermostat Test” in this section.
10. Clean the thermostat housing and the cylinder head
mating surfaces.

ENGINE COOLING 1D – 11
DAEWOO V–121 BL4
Installation Procedure
1. Install the thermostat into the thermostat housing
by pressing the thermostat mounting flange down-
ward and then rotating the flange counterclockwise.
Rotate the thermostat mounting flange until it is
seated in the thermostat housing recesses.
2. Coat the sealing surface of a new seal ring with
Lubriplater®.
3. Install a new seal ring into the recess in the thermo-
stat housing.
4. Install the thermostat housing to the cylinder head.
5. Secure the thermostat housing to the cylinder head
with the mounting bolts.
Tighten
Tighten the thermostat housing mounting bolts to 15
NSm (11 lb–ft).
6. Connect the upper radiator hose to the thermostat
housing.
7. Secure the upper radiator hose to the thermostat
housing with a hose clamp.
8. Refill the engine cooling system. Refer to ”Draining
and Refilling the Cooling System” in this section.
WATER PUMP
Removal Procedure
1. Drain the engine cooling system to a level below
the thermostat housing. Refer to ”Draining and Re-
filling the Cooling System” in this section.
2. Remove the timing belt. Refer to Section 1C DOHC
Engine Mechanical.
3. Remove the timing belt tension roller retaining bolt.
4. Remove the timing belt tension roller.

1D – 14IENGINE COOLING
DAEWOO V–121 BL4
Tighten
Tighten the fan motor retaining screws to 4 NSm (35
lb–in).
3. Turn over the fan shroud assembly.
4. Install the fan to the fan shroud assembly with the
single nut in the center of the fan hub.
Tighten
Tighten the fan motor nut to 3.2 NSm (28 lb–in).
5. Install the fan shroud assembly to the radiator.
Important : Be careful to seat the mounting post on the
fan shroud into the socket at the radiator left tank. Be sure
to slip the tab at the bottom edge of the shroud into the re-
taining clip near the center of the radiator.
6. Secure the shroud to the top of the radiator with the
mounting bolts.
Tighten
Tighten the fan assembly mounting bolts to 4 NSm (35
lb–in).
7. Connect the cooling fan electrical connector.
8. Connect the negative battery cable.
SURGE TANK
Removal Procedure
CAUTION : To prevent personal injury, do not remove
the surge tank cap while the engine and the radiator
are hot, because the heat causes the system to re-
main under pressure. Scalding fluid and steam may
be blown out under pressure.
1. Drain the engine coolant to below the level of the
surge tank.
2. Loosen the return hose clamp and disconnect the
return hose from the top of the surge tank.

1D – 16IENGINE COOLING
DAEWOO V–121 BL4
RADIATOR
Removal Procedure
1. Disconnect the negative battery cable.
2. Drain the engine cooling system. Refer to ”Draining
and Refilling the Cooling System” in this section.
3. Remove the main and the auxiliary cooling fans.
Refer to ”Electric Cooling Fan – Main or Auxiliary”
in this section.
4. Remove the upper radiator retaining bolt.
5. Remove the upper radiator retaining bracket.
6. Remove the upper radiator hose clamp.
7. Disconnect the upper radiator hose from the radia-
tor.
8. Remove the hose clamp from the surge tank hose
at the radiator.
9. Disconnect the surge tank hose from the radiator.
10. Remove the lower radiator hose clamp.
11. Disconnect the lower radiator hose from the radia-
tor.
12. Disconnect the transaxle cooler pipes from the low-
er radiator tank, if equipped.
13. Remove the bolt and the transaxle pipe support
clamp from the radiator.
14. Remove the radiator from the vehicle.
Important : The radiator still contains a substantial
amount of coolant. Drain the remainder of the coolant from
the radiator into a drain pan.
Installation Procedure
1. Set the radiator into place in the vehicle with the
radiator bottom posts in the rubber shock bumpers.
2. Connect the transaxle cooler pipes to the lower ra-
diator tank, if equipped.
3. Install the transaxle pipe and support clamp to the
radiator with a bolt.
4. Connect the surge tank hose to the radiator.
5. Secure the surge tank hose with a hose clamp.
6. Connect the upper radiator hose and the lower ra-
diator hose to the radiator.
7. Secure each hose with a hose clamp.
8. Position the radiator retainers in place.
9. Install the upper radiator retainer bracket.
10. Install the upper radiator retaining bolt.

ENGINE COOLING 1D – 17
DAEWOO V–121 BL4
11. Install the main and the auxiliary cooling fans. Refer
to ”Electric Cooling Fan – Main or Auxiliary” in this
section.
12. Refill the engine cooling system. Refer to ”Draining
and Refilling the Cooling System” in this section.
13. Connect the negative battery cable.
Tighten
Tighten the radiator retaining bolt to 8 NSm (71 lb–in).

1D – 18IENGINE 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. This 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.
This 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. 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 this 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.
WATER PUMP
The belt–driven centrifugal water pump consists of an im-
peller, a drive shaft, and a belt pulley. The water pump is
mounted on the front of the transverse–mounted engine,
and is driven by the timing belt.
The impeller is supported by a completely sealed bearing.
The water 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°C (189°F) and is fully
open at 102°C (216°F). The thermostat closes at 86°C
(187°F).

ENGINE COOLING 1D – 19
DAEWOO V–121 BL4
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.
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 condition (A/C)–equipped vehicles. This
helps to speed cooling when the vehicle is at idle or moving
at low speeds.
1.4L DOHC engine fan size is 340mm (13.4 in.) and
1.6L/1.8L DOHC engine 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 support 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.
Non–A/C models have only the main fan.
A/C OFF or Non–A/C Model (1.4L/1.6L)
S The cooling fans are actuated by the electronic
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 ECM will turn the cooling fans on at low speed
when the coolant temperature reaches 97.5°C
(207.5°F) and the cooling fans off at 95.25°C
(203.4°F).
A/C OFF or Non–A/C Model (1.8L)
S The cooling fans are actuated by the electronic
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 ECM will turn the cooling fans on at low speed
when the coolant temperature reaches 93°C
(199°F) and the cooling fans off at 90°C (194°F).
A/C ON (1.4L/1.6L)
S The ECM will turn the cooling fans on at low speed
when the A/C system is on. The ECM will change
to high speed when the coolant temperature reach-
es 101.25°C (214°F) or the high side A/C pressure
reaches 1859 kPa (270 psi).
S The cooling fans will return to low speed when the
coolant temperature reaches 99°C (210°F) and the
high side A/C pressure reaches 1449 kPa (210 psi).
A/C ON (1.8L)
S The ECM will turn the cooling fans on at low speed
when the A/C system is on. The ECM will change
to high speed when the coolant temperature reach-
es 97°C (207°F) or the high side A/C pressure
reaches 1859 kPa (270 psi).
S The cooling fans will return to low speed when the
coolant temperature reaches 94°C (201°F) and the
high side A/C pressure reaches 1449 kPa (210 psi).
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.