Lexus LX 470 1998 Owner's Manual page 214

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.
CAUTION
D Do not pump the brake pedal if the engine stalls. Each push
on the pedal uses up your brake fluid pressure reserve.
D 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 be
longer.
STARTING AND DRIVING
Anti−lock brake system
The anti−lock brake system is designed to automatically help
prevent lock−up of the wheels during a sudden brake or braking
on slippery road surfaces. This assists in providing directional
stability and steering performance of the vehicle under these
circumstances.
The anti−lock brake 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).
You may hear a sound in the engine compartment for a few seconds
when the engine is started or just after the vehicle is started. This
means that the anti−lock brake system is in the self−check mode, and
does not indicate a malfunction.
Effective way to press the ABS brake pedal: When the anti−lock
brake system function is in action, you may feel the brake pedal
pulsating and hear a noise. In this situation, to let the anti−lock brake
system work for you, just hold the brake pedal down more firmly.
Do not pump the brake. This will result in reduced braking
performance.
The brake pedal pulsation caused by the anti−lock brake system may
indicate hazardous road surface conditions. Although the anti−lock
brake system assists in providing vehicle control, it is still important
to drive with all due care, because the anti−lock brake system cannot
overcome the laws of physics that act on your vehicle:
D Braking capability is dependent on tire friction with the road
surface.
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