1991 LEXUS SC400 engine

BO6847
mm (in.)
(Three-Dimensional Distance)
Hole dia.
10 (0.39) screw
14 (0.55) screw
10 (0.39) screw
Name
Propeller shaft center support bearing installation nut
Rear suspension member installation nut
Suspension member bracket installation nut rear = outer
Symbol
K, k
N, n
P, p
Hole dia.
9 (0.35)
18 (0.71)
10 (0.39) screw
Name
Front crossmember working hole
Front suspension crossmember installation nut
Engine rear mounting member installation hole
Symbol
B, bH, h J, j
UNDER BODY (Cont'd)
BODY DIMENSIONSDI-5
WhereEverybodyKnowsYourName

BO6847
NOTICE: True up the mounting section ofthe front airbag sensor very carefully and
accurately so that the sensor can bemounted at the correct angle.
Imaginary
Standard
Line
mm (in.)
(Two-Dimensional Distance)
Hote dia.
10 (0.39) nut
10 (0.33) nut
18 (0.71)
14 (0.55) nut 9 (0.35)
Name
Engine rear mounting member installation nut-front Propeller shaft center support bearing installation nut
Front floor reinforcement standard hole
Rear suspension member installation nut Rear spring support hole-front
Symbol
J, j
K, k
L, l
N, n
O, o
Hole dia.
9 (0.35)
9 (0.35)
8 (0.31) nut
13 y11 (0.51 y0.43)14 (0.55) nut
Name
Front crossmember working hole
Airbag front sensor installation hole
Airbag front sensor installation nut Front spring support hole = outer
Front suspension crossmember installation nut
Symbol
B, b
C, c
E, e
G, g H, h
UNDER BODY (Cont'd)
BODY DIMENSIONSDI-7
WhereEverybodyKnowsYourName

Shift Lock ECU
Tilt and Power
Telescopic ECU
Airbag ECU
Cruise Control ECU Engine ECUABS and Traction ECU
(w/ Traction System) or
ABS ECU
(w/o Traction System)
Theft Deterrent and
Door Lock ECU
(w/ Traction System)
Traction ECU
Remote Control Mirror ECU A/C Control Amplifier
PPS ECU
Engine Cooling Fan ECU
Component to be aligned
Section of repair manual
for relevant model year
Front Wheels Suspension and Axle (SA) section
Rear Wheels Suspension and Axle (SA) section
Propeller Shaft Propeller Shaft (PR) section
2. BRAKE SYSTEM
The brake system is one of the most important safety components. Always \
follow the directions and
notes given in section BR of the repair manual for the relevant model ye\
ar when handling brake sys-
tem parts.
NOTICE: When repairing the brake master cylinder or TRAC system, bleed t\
he air out of the TRAC
system.
3. DRIVE TRAIN AND CHASSIS
The drive train and chassis are components that can have great effects on the running performance
and vibration resistance of the vehicle. After installing components in \
the sections listed in the table
below, perform alignments to ensure correct mounting angles and dimensions. P\
articularly accurate
repair of the body must also be done to ensure correct alignment.
HINT: Correct procedures and special tools are required for alignment. Alway\
s follow the directionsgiven in the repair manual for the relevant model year during alignment \
and section DI of this manual.
4. ECU (ELECTRONIC CONTROL UNIT)
Locations of ECUs
INTRODUCTIONIN-8
WhereEverybodyKnowsYourName

INSTALLATION
PRE-WELDING MEASUREMENTS
Always take measurements
before installing underbody
or engine components
to insure correct assembly.
After installation, confirm
proper fit.POST-WELDING REFINISH-
ING
1. Always check the welded
spots to insure they are
secure.
2. When smoothing out the weld spots with a disc
grinder, be careful not to
grind off too much as this
would weaken the weld.
WELDING PRECAUTIONS
1. The number of welding spots
should be as follows.
Spot weld: 1.3 x No. of
manufacturer's spots.
Plug weld: More than No. of
manufacturer's plugs.
WRONG
OKAYWRONG
2. Plug welding should be done
with a MIG (Metal Inert Gas)
welder. Do not gas weld or
braze panels at areas other
than specified.
Safety Glass
Body
Measurement
Diagrams
SPOT WELDING PRECAUTIONS
SPOT WELD LOCATIONS
Try to avoid welding over
previous spots. 1. The shape of the welding
tip point has an effect on
the strength of the weld.
2. Always insure that the seams and welding tip are
free of paint.
Old
Spot
Locations New Spot
Locations
Tip Cutter
INTRODUCTIONIN-13
WhereEverybodyKnowsYourName

TORQUE SPECIFICATIONS
Part tightenedNVmkgf Vcmft Vlbf
Engine drain plug X Cylinder block1818013
Coolant filler plug X Water inlet housing44450 33
Water pump X Cylinder block18185 13
Water inlet housing X Water pump18185 13
Water inlet X Water inlet housing18185 13
Radiator fan shroud X Radiator4.950 43 in. Vlbf
Radiator X Body12120 9
Cooling fan reservoir tank X Radiator fan shroud4.950 43 in. Vlbf
Cooling fan inlet pipe X Radiator fan shroud4.950 43 in. Vlbf
Cooling fan pressure hose X Hydraulic motor64650 47
Radiator reservoir tank X Upper radiator support4.950 43 in. Vlbf
Radiator reservoir tank X Radiator reservoir tank support4.950 43 in. Vlbf
Hydraulic pump rear housing X End plug (for spool valve)19200 14
Hydraulic pump front housing X Rear housing21210 15
Hydraulic pump pulley X Drive shaft59600 43
Solenoid valve X Hydraulic pump rear housing39400 28
Hydraulic pump suction port union X Rear housing13135 10
 Hydraulic pump X Cylinder block 12 mm head 16 160 12
  14 mm head 20 310 22
\
 \
Cooling fan pressure hose X Hydraulic pump 64 650 47
\
 \
RH No.2 timing belt cover X Cylinder block 16 160 12
\
 \
Drive belt idler pulley X Hydraulic pump 37 380 27
\
 \
A/C compressor X Hydraulic pump 49 500 36
\
 \
A/C compressor X Cylinder block 49 500 36\
 \
A/C compressor stay X Oil filter bracket 29 300 22\
 \
Hydraulic motor cover X Motor housing 28 290 21\
 
\

\
Hydraulic motor X Radiator fan shroud
 

4.9
 

50
 

43 in.
Vlbf
\
 \
Cooling fan X Hydraulic motor 15 150 11
\
 \
Cooling fan oil cooler X Body 18 180 13
\
 \
Water temperature sensor X Radiator 7.4 75 65 in. Vlbf
±
COOLIING SYSTEM Service SpecificationsCO±65
WhereEverybodyKnowsYourName

DESCRIPTION
This engine utilizes a pressurized forced circulation cooling system which i\
ncludes a hermostat equipped
with a by±pass valve mounted on the inlet side. The cooling system is composed of the water jacket (inside the cylinder bl\
ock and cylinderhead), radiator,
water pump, thermostat, cooling fan, hoses and other components.
OPERATION
CO±2±
COOLIING SYSTEM Description
WhereEverybodyKnowsYourName

DESCRIPTION
This engine utilizes a pressurized forced circulation cooling system whi\
ch includes a hermostat equipped
with a by±pass valve mounted on the inlet side. The cooling system is composed of the water jacket (inside the cylinder bl\
ock and cylinderhead), radiator,
water pump, thermostat, cooling fan, hoses and other components.
OPERATION
CO±2±
COOLIING SYSTEM Description
WhereEverybodyKnowsYourName

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)
±
COOLIING SYSTEM DescriptionCO±3
WhereEverybodyKnowsYourName