Lexus SC300 / Lexus SC400. Manual - part 316

Coolant which is heated in the water jacket is pumped to the radiator, through which a cooling fan blows

air to cool the coolant as it passes through. Coolant which has been cooled is then sent back to the engine by
the water pump, where it cools the engine.

The water jacket is a network of channels in the shell of the cylinder block and cylinderhead through which

coolant passes. It is designed to provide adequate cooling through the cylinders and combustion chambers
which become heated during engine operation.
RADIATOR

The radiator performs the function of cooling the coolant which has passed through the waterjacket and

become hot, and it is mounted in the front of the vehicle. The radiator consists of an upper tank and lower tank,
and a core which connects the two tanks. The upper tank contains the inlet for coolant from the water jacket
and the filler inlet. It also has a hose attached through which excess coolant or steam can flow. The lower tank
contains the outlet for coolant and drain plug. The core contains many tubes through which coolant flows from
the upper tank to the lower tank as well as cooling fins which radiate heat away from the coolant in the tubes.
The air sucked through the radiator by the cooling fan, as well as the wind generated by the vehicle’s travel,
passes through the radiator, cooling the coolant. Models with automatic transmission include an automatic
transmission fluid cooler built into the lower tank of the radiator. A cooling fan is mounted behind radiator to assist
the flow of air through the radiator. When the coolant temperature is low, the fan operates slowly to help the warm
up, and when the coolant temperature becomes high, the fan speed is increased to provide the air flow required
for cooling.
RADIATOR CAP (on Reservoir Tank)

The radiator cap is a pressure type cap which seals the radiator, resulting in pressurization of the radiator

as the coolant expands. The pressurization prevents the coolant from boiling even when the coolant tempera-
ture exceeds 100

C (212

F). A relief valve (pressurization valve) and a vacuum valve (negative pressure valve)

are built into the radiator cap. The relief valve opens and lets steam escape through the overflow pipe when
the pressure generated inside the cooling system exceeds the limit (coolant temperature: 110–120

(230–248

F) pressure; 29.4–98.1 kPa (0.3–1.0 kgf/cm2, 4.3–14.2 psi)). The vacuum valve opens to alleviate

the vacuum which develops in the coolant system after the engine is stopped and the coolant temperature
drops.
RESERVOIR TANK

The purpose of the reservoir tank is to catch coolant overflows created by volumetrix expansion when the

coolant temperature increases. The cap of the reservoir tank is a pressure type which prevents deterioration
of the LLC (Long Life Coolant) caused by contact with atmospheric air, increases vaporization performance and
reduces loss of the coolant volume.
WATER PUMP

The water pump is mounted on the front of the cylinder block and driven by the reverse side of the timing

belt.
THERMOSTAT

The thermostat has a wax type by–pass valve and is mounted in the water inlet housing. The thermostat

begins to open at the temperature of 80

C (180

F). When the coolant temperature is low, the valve closes to

prevent coolant flow to the radiator, thus permitting the engine to warm up rapidly. When the by–pass valve
opens the by–pass circuit, the engine coolant continues to circulate inside the engine, quickly and uniformly
warming up to the appropriate temperature. When the coolant temperature is high, the valve opens and coolant
flows to the radiator where it is cooled. When the wax inside the thermostat is heated, it expands and thus
creates pressure which overpowers the force of the spring which keeps the valve closed. When the wax cools,
its contraction causes the force of the spring to take effect once more, closing the valve.

ELECTRONICALLY CONTROLLED HYDRAULIC COOLING FAN (See page

CO–22

)

–

COOLIING SYSTEM

Description

CO–3

PREPARATION

SST (SPECIAL SERVICE TOOLS)

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Illustration

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Part No.

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Part Name

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Note

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09278–54012

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Drive Shaft Holding Tool

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Hydraulic pump pulley

ÑÑÑÑÑÑÑÑÑ

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09286–46011

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Injection Pump
Spline Shaft Puller

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

Hydraulic pump pulley

ÑÑÑÑÑÑÑÑÑ

ÑÑÑÑÑÑ

09620–30010

ÑÑÑÑÑÑÑÑ

Steering Gear Box
Replacer Set

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

ÑÑÑÑÑÑÑÑÑ

ÑÑÑÑÑÑ

(09627–30010)

ÑÑÑÑÑÑÑÑ

Steering Sector Shaft
Bushing Replacer

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

Oil seal for hydraulic motor

ÑÑÑÑÑÑÑÑÑ

ÑÑÑÑÑÑ

(09631–00020)

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(Handle)

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

Oil seal for hydraulic motor

ÑÑÑÑÑÑÑÑÑ

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09631–10030

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Oil Seal Remover

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Oil seal for hydraulic pump

ÑÑÑÑÑÑÑÑÑ

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09843–18020

ÑÑÑÑÑÑÑÑ

Diagnosis Check
Wire

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RECOMMENDED TOOLS

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Illustration

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Part No.

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Part Name

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Note

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09025–00010

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Small Torque
Wrench

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For measuring preload

ÑÑÑÑÑÑÑÑÑ

ÑÑÑÑÑÑ

09082–00015

ÑÑÑÑÑÑÑÑ

TOYOTA
Electrical tester

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

ÑÑÑÑÑÑÑÑÑ

ÑÑÑÑÑÑ

09200–00010

ÑÑÑÑÑÑÑÑ

Engine Adjust
Kit

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

ÑÑÑÑÑÑÑÑÑ

ÑÑÑÑÑÑ

09258–00030

ÑÑÑÑÑÑÑÑ

Hose Plug Set

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

Plug for the vacuum hose, oil hose ect.

ÑÑÑÑÑÑÑÑÑ

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09904–00010

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Expander
Set

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Oil seal for hydraulic pump

ÑÑÑÑÑÑÑÑÑ

ÑÑÑÑÑÑ

09905–00013

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Snap Ring
Pliers

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Oil seal for hydraulic pump

CO–4

–

COOLIING SYSTEM

Preparation

EQUIPMENT

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Part Name

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Note

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Caliper gauge

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

Hydraulic pump, Hydraulic motor

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Micrometer

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Hydraulic pump, Hydraulic motor

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Precision straight edge

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Hydraulic pump, Hydraulic motor

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Pressure gauge

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ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

Radiator cap tester

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ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

Thermometer

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ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

Torque wrench

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ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

Vernier caliper

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Hydraulic pump

COOLANT

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Item

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Capacity

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Classification

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Item

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Liters

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US qts

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lmp. qts

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Classification

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Engine coolant

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10.8

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11.4

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9.5

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Ethylene–glycol base

LUBRICANT

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Item

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Capacity

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Classification

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Cooling fan fluid

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–

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ATF DEXRON



SSM (SPECIAL SERVICE MATERIALS)

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Part Name

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Part No.

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Use etc.

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Seal packing 1282B,
Three bond 1282B or equivalent

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08826–00100

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Water pump, Water inlet housing

–

COOLIING SYSTEM

Preparation

CO–5

CHECK AND REPLACEMENT OF
ENGINE COOLANT

1. CHECK

ENGINE COOLANT LEVEL AT RESERVOIR TANK

The coolant level should be between the ”LOW” and ”FULL”
lines at low temperature.
If low, check for leaks and add coolant up to the ”FULL” line.

CHECK ENGINE COOLANT QUALITY
There should be no excessive deposits of rust or scales
around the radiator cap or radiator filler hole, and the coolant
should be free from oil.
If excessively dirty, replace the coolant

REPLACE ENGINE COOLANT
(a) Remove the radiator cap.
CAUTION: To avoid the danger of being burned, do not
remove it while the engine and radiator are still hot, as
fluid and steam can be blown out under pressure.
(b) Drain the coolant from the radiator drain cock and

engine drain plug.

Torque

(Engine drain plug):

29 N

⋅

m (300 kgf

⋅

cm, 22 ft

⋅

lbf)

(d) Fill the system with coolant.

•

Use a good brand of ethylene–glycol base coolant,
mixed according to the manufacturer’s direction.

•

Using coolant which includes more than 50 %
ethylene–glycol (but not more than 70%) is
recommended.

NOTICE:

•

Do not use alcohol type coolant.

•

The coolant should be mixed with demineralized water or

distilled water.

Coolant capacity (w/ Heater):

M/T 8.5 liters (9.0 US qts, 7.5 Imp. qts)

A/T 8.4 liters (8.9 US qts, 7.4 Imp. qts)

(e)  Install the radiator cap.
(f)  Start the engine and check for leaks.
(g)  Recheck the coolant level and refill as necessary.

–

COOLING SYSTEM

Check and Replacement of Engine Coolant

CO–5

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