2008 LEXUS RX400H cooling

26
1-1. Hybrid system
RX400h_U
■After the 12-volt battery has discharged or has been changed or removed
The gasoline engine may not stop even if the vehicle is running on the hybrid battery
(traction battery). If this continues for a few days, contact your Lexus dealer.
■Sounds and vibrations specific to a hybrid vehicle
There may be no engine sounds or vibration even though the vehicle is able to
move. Always put the shift lever in P when parked.
The following sounds or vibrations may occur when the hybrid system is operating,
and are not a malfunction.
●Motor sounds may be heard from the engine compartment.
●Sounds may be heard from the hybrid battery (traction battery) behind the rear
seat when the hybrid system starts or stops.
●Sounds may be heard from the transmission when the hybrid system starts or
stops, or while the vehicle is idling.
●Engine sounds may be heard when accelerating sharply.
●Sounds may be heard from the regenerative brake when you press the brake
pedal.
●Vibration may be felt when the gasoline engine starts or stops.
●You may hear cooling fan sounds coming from the air intake vents under the
rear seat.
■Maintenance, repair, recycling, and disposal
Contact your Lexus dealer regarding maintenance, repair, recycling and disposal.
Do not dispose of the vehicle yourself.

28
1-1. Hybrid system
RX400h_U■
Hybrid battery air vent
There is an air intake vent under
the rear seats to cooling the hybrid
battery (traction battery). If the
vent becomes blocked, the hybrid
battery may overheat, leading to a
reduction in hybrid battery output.
Emergency shut off system
The emergency shut off system blocks off the high voltage current and
stops the fuel pump to minimize the r isk of electrocution and fuel leakage
when a certain level of impact is detected by the impact sensor. If the
emergency shut off system activates, your vehicle will not restart. To
restart the hybrid system, contact your Lexus dealer.
Energy monitor/consumption screen
You can view the status of your hybr id system on the multi-information
display ( →P. 143) and the navigation system screen. The following
images are examples only, and may vary slightly from actual conditions.
■ Energy monitor
● How to display on the navigation system screen:
Press INFO.
Touch on the Information screen.
If the Consumption screen is displayed, touch .
● How to display on the multi-information display:
Push the button several times to select the energy moni-
tor display.
STEP1
STEP2
STEP1

190
2-5. Driving information
RX400h_U
Connecting trailer lightsWith tow hitch receiver
Use the socket located under the rear bumper.
Without tow hitch receiver
Use the wire harness stored in the rear end under body.
■Front Emblem
■Before towing
Check that the following conditions are met:
●The vehicle's tires are properly inflated. ( →P. 3 4 0 )
●Trailer tires are inflated according to the trailer manufacturer's recommendation.
●All trailer lights work
●All lights work each time you connect them.
●The trailer ball is set up at the proper height for the coupler on the trailer.
●The vehicle remains level when a loaded or unloaded trailer is hitched. Do not
drive if the vehicle is not level, and check for improper tongue load, overloading,
worn suspension, or other possible causes.
●The trailer cargo is securely loaded.
●The rear view mirrors conform to all applicable federal, state/provincial or local
regulations. If they do not, install rear view mirrors appropriate for towing pur-
poses.
With towing package
Without towing package
On vehicles with a towing package, the
front emblem has openings, which are
designed to improve the cooling perfor-
mance.

312
4-3. Do-it-yourself maintenance
RX400h_U
CAUTION
The engine compartment contains many mechanisms and fluids that may move sud-
denly, become hot, or become electrically energized. To avoid death or serious injury:
■When working on the engine compartment
●Keep hands, clothing, and tools away from the moving fan and engine drive belt.
●Be careful not to touch the engine, inverter, radiator, exhaust manifold, etc. right
after driving as they may be hot. Oil and other fluids may also be hot.
●Do not leave anything that may burn easily, such as paper or rags, in the engine
compartment.
●Do not smoke, cause sparks or expose an open flame to fuel or the battery. Fuel
and battery fumes are flammable.
●Be extremely cautious when working on the battery. It contains poisonous and
corrosive sulfuric acid.
●Never touch, disassemble, remove or replace the high voltage parts, cables and
their connectors. It can cause severe burns or electric shock that may result in
death or serious injury.
●When the hybrid system is operating with the READY light on, the engine may
suddenly start in some cases. When you inspect the engine compartment, be
sure to turn off the hybrid system.
■When working near the electric cooling fan or radiator grille
Be sure the engine switch is off.
With the engine switch on, the electric cooling fan may automatically start to run if
the air conditioning is on and/or the coolant temperature is high. (→P. 3 2 5 )
■Safety glasses
Wear safety glasses to prevent flying or falling material, fluid spray, etc. from getting
in the eyes.
NOTICE
■If you remove the air cleaner:
Driving with the air filter removed may cause excessive engine wear due to dirt in
the air. Also a backfire could cause a fire in the engine compartment.

316
4-3. Do-it-yourself maintenance
RX400h_U
Engine compartment
Brake fluid reservoir(→P. 325)
Engine oil level dipstick (→P. 318)
Engine oil filler cap (→P. 318)
Power control unit coolant
reservoir ( →P. 323)
Fuse boxes ( →P. 352)Engine coolant radiator
(→P. 325)
Condenser ( →P. 325)
Power control unit coolant
radiator ( →P. 325)
Electric cooling fans
Engine coolant reservoir (→P. 323)
12-volt battery ( →P. 327)
Washer fluid tank (→P. 329)

324
4-3. Do-it-yourself maintenance
RX400h_U
■If the coolant level drops within a short time after replenishing
Visually check the radiator, hoses, reservoir cap, radiator cap, drain cock and water
pump.
If you cannot find a leak, have your Lexus dealer pressure test the cap and check for
leaks in the cooling system.
■Coolant selection
Only use Toyota Super Long Life Coolant or similar high quality ethylene glycol
based non-silicate, non-amine, non-nitrite, and non-borate coolant with long-life
hybrid organic acid technology.U.S.A.: Toyota Super Long Life Coolant is a mixture of 50% coolant and 50% deionized water. (Enabled: -31 °F [-35 °C])
Canada: Toyota Super Long Life Coolant is a mixture of 55% coolant and 45% deionized water. (Enabled: -44 °F [-42 °C])
For more details about coolant, contact your Lexus dealer.
CAUTION
■When the coolant may be hot
Do not remove the radiator cap.
The cooling system may be under pressure and may spray hot coolant if the cap is
removed, causing burns or other injuries.
NOTICE
■When adding the coolant
Coolant is neither plain water not straight antifreeze. The correct mixture of water
and antifreeze must be used to provide proper lubrication, corrosion protection
and cooling. Be sure to read the antifreeze or coolant label.
■If you spill coolant
Be sure to wash it off with water to prevent it damaging parts or paint.

355
4-3. Do-it-yourself maintenance
4
Maintenance and care
RX400h_U
Fuse layout and amperage ratings■ Engine compartment (type A)
FuseAmpereCircuit
1ABS MTR230Electronically controlled brake system
2ETCS10Hybrid system
3DC/DC-S10Hybrid system
4ABS NO.210Electronically controlled brake system
5ABS NO.110Electronically controlled brake system
6BATT FAN15Hybrid system
7ABS NO.315Electronically controlled brake system
8OIL PUMP10Transaxle fluid cooling system
9ABS MTR130Electronically controlled brake system
10ST7. 5Hybrid system

356
4-3. Do-it-yourself maintenance
RX400h_U■
Engine compartment (type B)
FuseAmpereCircuit
11HEATER50Air conditioning system, “WATER
PUMP” fuse
12IG130“SEAT HTR” fuse
13H-LP CLN30Headlight cleaner
14RR DEF40Rear window defogger
15RDI FAN No.140Electric cooling fan
16DC/DC120Hybrid system
17DRL7. 5Daytime running light system
18H-LP L LWR15Left-hand headlight (low beam)
19H-LP L UPR15Left-hand headlight
20H-LP R UPR15Right-hand headlight (high beam)
21PER OUTLET
NO.220Po w e r o u t l e t ( 1 1 5 VAC )
22TOW I N G30Trailer lights
23PBD30Power back door