2006 Lexus GS300 brakes

STARTING AND DRIVING
427
BRAKE SYSTEM
This brake system has 2 independent hydraulic circuits. If
either circuit should fail, the other will still work. However, the
pedal will be harder to press, and your stopping distance will
increase. Also, the brake system warning light may come on.
CAUTION
Do not drive your vehicle with only a single brake
system. Have your brakes fixed immediately.
Brake booster
The brake booster uses brake fluid pressurized by the pump
(GS430) or engine vacuum (GS300) to power−assist the
brakes. If the brake booster fails during driving, the brake
system warning light (red) comes on. In this case, the brakes
may not work properly. If they do not work well, depress the
brake pedal firmly. If the brake system warning light (red)
comes on, immediately stop your vehicle and contact your
Lexus dealer.
GS430 only—Either of the following conditions may
occur, but does not indicate a malfunction:
The brake system warning light (red) may stay on for about
60 seconds after the engine is started. It is normal if the light
turns off after a while.
Depressing the brake pedal repeatedly may turn on the
brake system warning light (red). It is normal if the light goes
out after a few seconds.GS430:
You may hear a small sound in the engine compartment after
the engine is started or the brake pedal is depressed
repeatedly. This is a pump pulsating sound of the brake
system, and it is not a malfunction.
GS300:
If the engine should stop while you are driving, you can bring
the vehicle to a stop with normal pedal pressure. There is
enough reserved vacuum for one or two stops—but no more!
CAUTION
Do not pump the brake pedal if the engine stalls.
Each push on the pedal uses up your brake fluid
pressure reserve.
Even if the power assist is completely lost, the brakes
will still work. But you will have to push the pedal
hard, much harder than normal. And your braking
distance will increase.

STARTING AND DRIVING
431
Drum−in−disc type parking brake system
Your vehicle has a drum−in−disc type parking brake system.
This type of brake system needs bedding−down of the brake
shoes periodically or whenever the parking brake shoes
and/or drums are replaced.
Have your Lexus dealer perform the bedding−down.
Brake assist system
When you slam the brakes on, the brake assist system
judges as an emergency stop and provides more powerful
braking for a driver who cannot hold down the brake pedal
firmly.
When you slam the brakes on, more powerful braking will be
applied. At this time, you may hear a sound in the engine
compartment and feel the vibrations of the brake pedal. This
does not indicate a malfunction.
The brake assist system becomes operative after the vehicle
has accelerated to a speed in excess of approximately 10 km/h
(6 mph). It stops operating when the vehicle decelerates to a
speed below approximately 5 km/h (3 mph).
The brake assist system may not work for about 60 seconds
after the engine is started.
For an explanation of this system’s warning light, see “ABS”
warning light on page 78 or 430.
BRAKE PAD WEAR LIMIT
INDICATORS
G31006
The brake pad wear limit indicators on your disc brakes
give a warning noise when the brake pads are worn to the
extent that replacement is required.
If you hear a squealing or scraping noise while driving, have
the brake pads checked and replaced by your Lexus dealer as
soon as possible. Expensive rotor damage can result if the
pads are not replaced when needed.
GS430 front brake only—
The high brake performance is achieved by proper wear of
brake pads and discs. As a result, the brake discs may wear
earlier than the ones on the conventional brake system.
When brake pads are replaced, brake disc thickness is
required to be measured.
It is dangerous to continue driving when brake pads and discs
have exceeded the wear limit.

STARTING AND DRIVING
435
CAUTION
If the low tire pressure warning light comes on, take
your vehicle to the nearest Lexus dealer or authorized
tire dealer or gas station as soon as possible, observing
the following instructions:
Decelerate as soon as possible to the most
appropriate speed that conditions permit. Do not
drive over 90 km/h (55 mph).
Avoid abrupt steering wheel maneuvering and
braking. If the vehicle tires deteriorate, you could
lose control of the steering wheel or the brakes,
causing death or serious injury.
The warning system may not activate immediately if
bursts or sudden air leakage should occur.
When the tyre pressure warning system warning light is
lit, one or more of your tyres is significantly
under−inflated. You should stop and check your tyres
as soon as possible, and inflate them to the proper
pressure as indicated on the vehicle’s tyre information
placard. Driving on a significantly under−inflated tire
causes the tyre to overheat and can lead to tyre failure.
Under−inflation also reduces fuel efficiency and tyre
tread life, and may affect the vehicle’s handling and
stopping ability. Each tyre, including the spare, should
be checked monthly when cold and set to the
recommended inflation pressure as specified in the
vehicle placard and owner’s manual.
NOTICE
Do not use liquid sealants for a flat tire as tire
pressure sensors will be damaged.
Take due care not to go over a curb stone and be
careful of the holes in the road because deflated tire
pressure affects tire cushion performance. The
wheels, tires, body, suspension and other
components could be damaged.
Your ground clearance is reduced if the run−flat tire
goes flat so avoid driving over obstacles and drive
slowly on rough, unpaved roads and speed bumps.
Also, do not attempt to go through an automatic car
wash as the vehicle may get caught, resulting in
damage.
When the tires must be replaced, have them replaced
by the nearest Lexus dealer or authorized tire dealer.
The tire pressure sensor will be affected by the
installation or removal of tires.
When the tires must be replaced, replace the
grommets for tire pressure sensors as well.

STARTING AND DRIVING
436Vehicles with standard tires:
Stop your vehicle at a safe place as soon as possible and
check that the tire inflation pressure is as specified on the tire
and loading information label. If the low tire pressure warning
light comes on even after tire inflation pressure adjustment, it
is probable that you have a flat tire. If the tire goes flat, change
to the spare tire. (See page 469.)
The spare tire is not equipped with the tire pressure sensor.
So, the low tire pressure warning light remains on even if the
spare tire is mounted.
The light goes off a few minutes after air is put into the deflated
tire.
CAUTION
If the low tire pressure warning light comes on, observe
the following instructions:
Decelerate as soon as possible to the most
appropriate speed that conditions permit.
Avoid abrupt steering wheel maneuvering and
braking. If the vehicle tires deteriorate, you could
lose control of the steering wheel or the brakes,
causing death or serious injury.
The warning system may not activate immediately if
bursts or sudden air leakage should occur.
When the tyre pressure warning system warning light is
lit, one or more of your tyres is significantly
under−inflated. You should stop and check your tyres
as soon as possible, and inflate them to the proper
pressure as indicated on the vehicle’s tyre information
placard. Driving on a significantly under−inflated tire
causes the tyre to overheat and can lead to tyre failure.
Under−inflation also reduces fuel efficiency and tyre
tread life, and may affect the vehicle’s handling and
stopping ability. Each tyre, including the spare, should
be checked monthly when cold and set to the
recommended inflation pressure as specified in the
vehicle placard and owner’s manual.