LEXUS SC400 1991 Service Repair Manual

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 coo\
led 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 bloc\
k and cylinderhead through which
coolant passes. It is designed to provide adequate cooling through the cylinders and combus\
tion chambers
which become heated during engine operation.
RADIATOR The radiator performs the function of cooling the coolant which has pass\
ed through the waterjacket and
become hot, and it is mounted in the front of the vehicle. The radiator consis\
ts 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 cool\
ant or steam can flow. The lower tank
contains the outlet for coolant and drain plug. The core contains many t\
ubes 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 ve\
hicle's travel,
passes through the radiator, cooling the coolant. Models with automatic transmission include an aut\
omatic
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 increas\
ed 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 boi\
ling even when the coolant tempera-
ture exceeds 100 5C (212 5F). A relief valve (pressurization valve) and a vacuum valve (negati\
ve pressure valve)
are built into the radiator cap. The relief valve opens and lets steam esca\
pe through the overflow pipe when
the pressure generated inside the cooling system exceeds the limit (coolant temperature: 110±120 5C
(230±248 5F) pressure; 29.4±98.1 kPa (0.3±1.0 kgf/cm2, 4.3±14.2 psi)). The vacuum v\
alve 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 t\
he reverse side of the timing
belt.
THERMOSTAT The thermostat has a wax type by±pass valve and is mounted in the wat\
er inlet housing. The thermostat
begins to open at the temperature of 80 5C (180 5F). 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)
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COOLIING SYSTEM DescriptionCO±3
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PREPARATION
SST (SPECIAL SERVICE TOOLS)
 Illustration Part No. Part Name Note
 


 

09278±54012
 

Drive Shaft Holding Tool
 


Hydraulic pump pulley
 




 



09286±46011
 




Injection Pump
Spline Shaft Puller
 




Hydraulic pump pulley
 




 



09620±30010
 




Steering Gear Box
Replacer Set
 




 




 



(09627±30010)
 




Steering Sector Shaft
Bushing Replacer
 




Oil seal for hydraulic motor
 




 




(09631±00020)
 




(Handle)
 




Oil seal for hydraulic motor
 




 




09631±10030
 




Oil Seal Remover
 




Oil seal for hydraulic pump
 




 




09843±18020
 




Diagnosis Check
Wire 




RECOMMENDED TOOLS 

Illustration
 

Part No.
 

Part Name
 

Note
 




 




09025±00010
 




Small Torque
Wrench 




For measuring preload
 


 

09082±00015 


TOYOTA
Electrical tester 


 




 



09200±00010
 




Engine Adjust
Kit
 




 




 



09258±00030
 



Hose Plug Set
 




Plug for the vacuum hose, oil hose ect.
 




 




09904±00010
 




Expander
Set
 




Oil seal for hydraulic pump
 




 




09905±00013
 




Snap Ring
Pliers
 




Oil seal for hydraulic pump
CO±4±
COOLIING SYSTEM Preparation
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EQUIPMENT
 Part Name\
 \
Note
 Caliper gauge\
 \
Hydraulic pump, Hydraulic motor
 Micrometer\
 \
Hydraulic pump, Hydraulic motor
 Precision straight edge\
 \
Hydraulic pump, Hydraulic motor Pressure gauge\
 \

 
Radiator cap tester\
 
\
 

Thermometer
\
 
\

\

 Torque wrench\
 \

 Vernier caliper\
 \
Hydraulic pump
COOLANT 

Item
 

Capacity
 

Classification
 
Item
 Liters US qts lmp. qts 
Classification
 Engine coolant 10.8 11.4 9.5 Ethylene±glycol base
LUBRICANT
 Item Capacity Classification
 Cooling fan fluid ± ATF DEXRON
[II
SSM (SPECIAL SERVICE MATERIALS) 

Part Name
 

Part No.
\
 

\
Use etc.
 


Seal packing 1282B,
Three bond 1282B or equivalent 


08826±00100\
 

\

Water pump, Water inlet housing
±
COOLIING SYSTEM PreparationCO±5
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CHECK AND REPLACEMENT OF
ENGINE COOLANT
1. CHECK ENGINE COOLANT LEVEL AT RESERVOIR TANK
The coolant level should be between the ºLOWº and ºFULLº
lines at low temperature.
If low, check for leaks and add coolant up to the ºFULLº line.
2. 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
3. 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 andengine drain plug.
(c) Close the drain cock and plug.
Torque (Engine drain plug):
29 NVm (300 kgf Vcm, 22 ft Vlbf)
(d) Fill the system with coolant.
w Use a good brand of ethylene±glycol base coolant,
mixed according to the manufacturer's direction.
w Using coolant which includes more than 50 %
ethylene±glycol (but not more than 70%) is
recommended.
NOTICE:
w Do not use alcohol type coolant.
w 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 CoolantCO±5
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CHECK AND REPLACEMENT OF
ENGINE COOLANT
1. CHECK ENGINE COOLANT LEVEL AT RESERVE TANKThe coolant level should be above the ºCOLD LEVELº at nor-
mal temperature (20 5C (68 5F)).
If low, check for leaks and add coolant up to the ºCOLD LEV-
ELº.
2. CHECK ENGINE COOLANT QUALITY There should not be any excessive deposits of rust or scales
around the radiator cap or reservoir tank filler hole, and the
coolant should be free from oil.
If excessively dirty, clean the coolant passages and replace
the coolant.
3. REPLACE ENGINE COOLANT (a) Remove the radiator cap from the reservoir tank.
CAUTION: To avoid the danger of being burned, do not
remove the cap while the engine and radiator are still hot,
as fluid and steam can be blown out under pressure.
(b) Remove the filler plug from the water inlet housing.
(c) Loosen the three drain plugs on the radiator and
cylinder block, drain the coolant from the radiator and
engine.
(d) Clean the coolant passages.
(e) Close the three drain plugs.
Torque (Engine drain plug):
18 NVm (180 kgf Vcm, 13 ft Vlbf)
CO±6±
COOLIING SYSTEM Check and Replacement of Engine Coolant
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(f) Slowly add coolant to water inlet housing until it is full.w Use a good brand of ethylene±glycol base coolant,
mixed according to the manufacturer's directions.
w Using coolant which includes more than 50%
ethylene±glycol (but not more 70%) than is
recommended.
NOTICE:
w Do not use alcohol type coolant.
w The coolant should be mixed with demineralized water or
distilled water.
Capacity (w/ Heater): 10.8 liters (11.4 US qts, 9.5 lmp. qts)
(g) Reinstall a new gasket and filler plug to the water inlethousing.
Torque: 44 N Vm (450 kgf Vcm, 33 ft Vlbf)
(h) Slowly add coolant to reservoir tank until it is full.
(i) Reinstall the radiator cap.
(j) Bleed the cooling system.
w Start the engine, and open the heater water valve.
w Maintain the engine speed at 2,000 rpm, and warm
up the engine.
(k) Check for leaks.
(l) Recheck the coolant level and refill as necessary.
±
COOLIING SYSTEM Check and Replacement of Engine CoolantCO±7
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WATER PUMP
COMPONENTS FOR REMOVAL AND
INSTALLATION
REMOVAL OF WATER PUMP
1. REMOVE TIMING BELT(See steps 1 to 35 on pages EM±35 to 43)
2. REMOVE RH IGNITION COIL (a) Disconnect the ignition coil connector.
(b) Remove the two bolts and ignition coil.
3. REMOVE WATER INLET AND INLET HOUSING (a) Disconnect the water by±pass hose from the water inlethousing.
CO±8
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COOLIING SYSTEM Water Pump
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(b) Remove the two bolts holding the water inlet housing tothe water pump.
(c) Pull out the water inlet and inlet housing assembly.
(d) Remove the O±ring from the water inlet housing.
4. REMOVE WATER PUMP (a) Remove the five mounting bolts, two stud bolts and nut.
(b) Remove the water pump by prying the portions betweenthe water pump and cylinder block with a screwdriver.
(c) Remove the O±ring from the water by±pass pipe.
INSPECTION OF WATER PUMP
INSPECT WATER PUMP
Turn the pulley and check that the water pump bearing
moves smoothly and quietly.
±
COOLIING SYSTEM Water PumpCO±9
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INSTALLATION OF WATER PUMP
(See Components on page CO±8)
1. INSTALL WATER PUMP (a) Remove any old packing (FIPG) material and be careful
not to drop any oil on the contact surfaces of the water
pump and cylinder block.
w Using a razor blade and gasket scraper, remove all
the old packing (FIPG) material from the gasket
surfaces and sealing groove.
w Thoroughly clean all components to remove all the
loose material.
w Using a non±residue solvent, clean both sealing
surfaces.
(b) Apply seal packing to the sealing groove of the water pump as shown in the illustration.
Seal packing: Part No. 08826±00100 or equivalent
w Install a nozzle that has been cut to a 2±3 mm
(0.08±0.12 in.) opening.
HINT: Avoid applying an excessive amount to the surface. w Parts must be assembled within 5 minutes of
application. Otherwise the material must be
removed and reapplied.
w Immediately remove nozzle from the tube and
reinstall cap.
(c) Install a new O±ring to the water by±pass pipe end.
(d) Apply soapy water to the O±ring.
(e) Connect the water by±pass pipe end to water pump.
(f) Install the water pump with the five bolts, two stud bolts and nut. Uniformly tighten the bolts, stud bolts and nut.
Torque: 18 N Vm (185 kgf Vcm, 13 ft Vlbf)
HINT: Use bolts 30 mm (1.18 in.) in length.
2. INSTALL WATER INLET AND INLET HOUSING (a) Remove any old packing (FIPG) material and be careful
not to drop any oil on the contact surfaces of the water
inlet housing and water pump.
w Using a razor blade and gasket scraper, remove all
the old packing (FIPG) material from the gasket
surfaces and sealing groove.
w Thoroughly clean all components to remove all the
loose material.
w Using a non±residue solvent, clean both sealing
surfaces.
CO±10
±
COOLIING SYSTEM Water Pump
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(b) Apply seal packing to the sealing groove of the waterinlet housing as shown in the illustration.
Seal packing: Part No. 08826±00100 or equivalent
w Install a nozzle that has been cut to a 2±3 mm
(0.08±0.12 in.) opening.
HINT: Avoid applying an excessive amount to the surface. w Parts must be assembled within 5 minutes of
application. Otherwise the material must be
removed and reapplied.
w Immediately remove nozzle from the tube and
reinstall cap.
(c) Install a new O±ring to the water inlet housing.
(d) Apply soapy water to the O±ring.
(e) Push the water inlet housing end into water pump hole.
(f) Install the water inlet and inlet housing assembly with the two bolts. alternately tighten the bolts.
Torque: 18 N Vm (185 kgf Vcm, 13 ft Vlbf)
HINT: Use bolts 25 mm (0.98 in.) in length.
(g) Connect the water by±pass hose to the water inlet
housing.
3. INSTALL RH IGNITION COIL (a) Install the ignition coil with the two bolts.
(b) Connect the ignition coil connector.
4. INSTALL TIMING BELT (See steps 4 to 43 on pages EM±47 to 57)
±
COOLIING SYSTEM Water PumpCO±11
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