2008 Lexus GS450h engine overheat

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2-1. Driving procedures
GS_HV_U
May 13, 2008 3:11 pm
CAUTION
■When driving the vehicle
●Do not shift the shift lever to “N” while the vehicle is moving.
Doing so may cause the engine brake not to operate properly and lead to an
accident.
●Do not turn the hybrid system off while driving. 
The power steering and brake actuator will not operate properly if the hybrid sys-
tem is off.
●Use engine braking (downshift) to maintain a safe speed when driving down a
steep hill. 
Using the brakes continuously may cause the brakes to overheat and lose effec-
tiveness. ( P. 144)
●When stopped on an inclined surface, use the brake pedal and parking brake to
prevent the vehicle from rolling backwa rd or forward and causing an accident.
●Be careful when driving on slippery surfaces, as the vehicle may spin or skid when
downshifting, rapidly accelerating, braking or turning.
●Do not adjust the position of the steering wheel, the seat, or the inside or outside
rear view mirrors while driving. 
Doing so may result in a loss of vehicle control that can cause accidents that may
result in death or serious injury.
●Always check that all passengers’ arms, heads or other parts of their bodies are
not outside the vehicle, as this may result in death or serious injury.
●Do not drive in excess of the speed limit. Even if the legal speed limit permits it, do
not drive over 85 mph (140 km/h) unless your vehicle has high-speed capability
tires. Driving over 85 mph (140 km/h) may result in tire failure, loss of control and
possible injury. Be sure to consult a tire dealer to determine whether the tires on
your vehicle are high-speed capability tires or not before driving at such speeds.
●The driver should pay attention to pedest rians when the vehicle is powered only
by the electric motor (traction motor). Because there is no engine sounds, the
pedestrians may misjudge the vehicle’s movement.

151
2-2. Instrument cluster
2
When driving
GS_HV_U
December 12, 2007 3:50 pm
NOTICE
■To prevent damage to the engine and its components
The engine may be overheating if the engine coolant temperature gauge is in the
red zone (“H”). In this case, immediately stop the vehicle in a safe place. Check the
engine after it has cooled completely. ( P. 5 3 8 )
■To activate the light sensitivity function properly
Do not affix a sticker or window tint to the rear window glass, or put an object
behind the rear seat.

538
5-2. Steps to take in an emergency
GS_HV_U
December 12, 2007 3:50 pm
If your vehicle overheats
If your hybrid system overheats:
Stop the vehicle in a safe place and turn off the air conditioning
system.
Check to see if steam is coming out from under the hood.
If you see steam: 
Stop the hybrid system and carefully lift the hood.
If you do not see steam: Leave the hybrid system running and carefully lift the hood.
Remove the engine compartment cover. ( P. 421)
Check to see if the cooling fan is operating.
If the fan is operating: 
Wait until the engine coolant temperature gauge begins to
fall and then stop the hybrid system.
If the fan is not operating: 
Stop the hybrid system immed iately and call your local
Lexus dealer.
After the hybrid system has
cooled down sufficiently, check
the coolant level and inspect the
radiator core (radiator) for any
leaks.STEP1
STEP2
STEP3
STEP4
STEP5

5
When trouble arises
539
5-2. Steps to take in an emergency
GS_HV_U
December 12, 2007 3:50 pm
■Overheating
In the following situations, your vehicle may be overheating.
●The engine coolant temperature gauge enters the red zone or a loss of power is
experienced.
●Steam is coming from under the hood.
●The message “HYBRID SYSTEM OVERHEAT” is displayed on the multi-infor-
mation display.
CAUTION
■To prevent an accident or injury when in specting under the hood of your vehicle
●Keep hands and clothing away from the fan and engine drive belt while the hybrid
system is running.
●Do not loosen the radiator cap while the hybrid system and radiator are hot. 
Serious injury, such as burns, may resu lt from hot coolant and steam released
under pressure.
Add coolant if necessary.
Water can be used in an emer-
gency measure if coolant is
unavailable. ( P. 5 4 8 )
Have the vehicle checked at your nearest Lexus dealer as soon as pos-
sible.
STEP6

585
Alphabetical index
GS_HV_U
December 12, 2007 3:50 pm
CareExterior ................................................... 402
Interior..................................................... 405
Seat belts ............................................... 406
Cargo capacity ....................................... 210
Cargo hooks ...........................................375
CD player/changer .............................257
Chains......................................................... 216
Child-protectors ....................................... 51
Child restraint system Definition....................................................113
Installation.................................................. 117
Installing CRS with lower 
anchors ................................................... 121
Installing CRS with seatbelts .......... 118
Installing CRS with top straps ....... 123
Child safety Airbag precautions ............................ 102
Battery precautions .............. 432, 537
Child restraint system .........................113
Child-protectors..................................... 51
How your child should wear 
the seatbelt ........................................... 69
Installing child restraints ..................... 117
Moon roof precautions ..................... 82
Power window lock switch .............. 77
Power window precautions.............79
Removed electronic key battery 
precautions ....................................... 455
Seat belt comfort guide......................67
Seat belt precautions.......................... 70
Seat heater precautions ................ 370
Trunk precautions .................................57
Cigarette lighter ....................................367 Cleaning
Exterior....................................................402
Interior .................................................... 405
Seat belts ............................................... 406
Clock ......................................................... 364
Coin holder .............................................360
Compass ................................................. 383
Condenser ..............................................428
Console box ........................................... 357
Cooling system Engine overheating.......................... 538
Cruise control Cruise control....................................... 166
Dynamic radar cruise control....... 169
Cup holders ............................................360
Curtain shield airbags............................ 95
Customizable features .......................569
Daytime running light system ........... 159
Defogger Rear window ........................................240
Side mirror.............................................240
Dimension................................................ 544
Dinghy towing ..........................................221
Display Energy flow .............................................. 27
Multi-information display ................ 155
Touch screen ....................................... 224
Trip information ................................... 156
Warning message ............................ 500
Do-it-yourself maintenance .............. 414
Door courtesy lights ............................352
Door pocket............................................. 361C
D

586
Alphabetical index
GS_HV_U
December 12, 2007 3:50 pm
DoorsDoor lock................................ 35, 47, 50
Rear door child protector .................. 51
Driver’s seat belt reminder light .....493
Driver’s seat position memory ...........60
Driving Correct posture .................................... 93
Procedures .............................................128
DVD player/changer.......................... 266
Electric power steering ..................... 200
Electronic key If the electronic key does 
not operate properly ......................531
Replacing battery .............................. 454
Emergency, in case of If a warning light turns on ................491
If a warning message is displayed ........................................... 500
If the electronic key does 
not operate properly ......................531
If the hybrid system 
will not start .......................................528
If the shift lever cannot be  shifted from “P”................................ 529
If the 12 volt battery is 
discharged ....................................... 534
If you have a flat tire ............... 517, 527
If you lose your keys.........................530
If you think something is 
wrong .................................................. 488
If your vehicle becomes stuck.......541
If your vehicle needs to be 
towed ................................................... 482
If your vehicle overheats ................538
Energy monitor......................................... 27 Engine
ACCESSORY mode .....................139
Compartment ..................................... 420
Hood ......................................................... 417
How to start the 
hybrid system..................................... 138
If the hybrid system 
will not start ....................................... 528
Overheating ........................................ 538
Power (ignition) switch .................... 138
Engine compartment cover ............... 421
Engine coolant temperature 
gauge ...................................................... 148
Engine/power control unit coolant Capacity ................................................ 548
Checking................................................ 427
Preparing and checking 
before winter...................................... 215
Engine oil Capacity .................................................547
Checking................................................ 422
Preparing and checking 
before winter...................................... 215
Engine oil maintenance data ........... 425
Event data recorder ............................ 489
First-aid kit storage belt ..................... 375
Floor mats ................................................ 374
Fluid Brake ........................................................429
Washer....................................................434
Fog lights Switch .......................................................... 161
Wattage ................................................. 552
Foot light .................................................. 352
E
F

588
Alphabetical index
GS_HV_U
December 12, 2007 3:50 pm
Instrument panel light control........... 149
Interior lightsInterior lights......................................... 353
Wattage.................................................. 552
Intuitive parking assist .......................... 180
Jack Positioning a floor jack..................... 418
Replacing the wheel........................... 517
Jack handle ............................................... 517
Keyless entry.............................................. 47
Keys If the electronic key does 
not operate properly ......................531
If you lose your keys.........................530
Key number plate ................................. 33
Keys ............................................................. 33
Mechanical key...................................... 33
Power (ignition) switch.................... 138
Wireless remote control key ...........47
Lexus Link System ................................387
Light bulbs Replacing ............................................... 474
Wattage.................................................. 552
Light sensitive optitron meter ........... 150
Lights Fog light switch ...................................... 161
Headlights switch ............................... 158
Interior lights list.................................. 352
Replacing light bulbs........................ 474
Turn signal lever ...................................146
Vanity lights .......................................... 363
Wattage.................................................. 552 Maintenance
Do-it-yourself maintenance........... 414
General maintenance....................... 410
Maintenance data ............................. 544
Maintenance requirements.......... 408
Meter Instrument panel light control ....... 149
Meters....................................................... 148
Micro dust and pollen filter .............. 236
Mirrors Inside rear view mirror ....................... 74
Side mirror heater............................. 240
Side mirrors.............................................. 75
Vanity mirrors ..................................... 363
Moon roof................................................... 80
MP3 disc.................................................. 262
Multi-information display ................... 155
Odometer ................................................ 148
Oil Engine oil................................................ 422
Opener Fuel filler door ........................................ 83
Hood ......................................................... 417
Trunk........................................................... 55
Outer foot lights.................................... 352
Outside rear view mirrors Adjusting and folding .......................... 75
Mirror position memory ................... 60
Outside temperature 
display .................................................... 365
Overhead console ...............................358
Overheating, Engine ..........................538
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GS_HV_U
December 12, 2007 3:50 pm
What to do if...
What to do if...
A tire puncturesP. 5 1 7 /527If you have a flat tire
The hybrid system does not start
P. 8 8Immobilizer system
P. 5 2 8If the hybrid system will not start
P. 5 3 4If the 12 volt battery is discharged
The shift lever cannot be 
moved outP. 5 2 9If the shift lever cannot be shifted 
from “P”
The engine coolant temperature
gauge enters the red zone
Steam can be seen coming 
from under the hood
P. 5 3 8If your vehicle overheats
The key is lostP. 5 3 0If you lose your keys
The battery runs outP. 5 3 4If the 12 volt battery is discharged
The doors cannot be lockedP. 5 0Doors
The horn begins to soundP. 9 0Alarm
The vehicle is stuck in mud or
sandP. 5 4 1If the vehicle becomes stuck