Chevrolet 2003 Impala Owner's Manual page 299

Notice:
Using the wrong fluid can badly damage brake
system parts. For example, just a few drops of
mineral-based oil, such as engine oil, in your
brake system can damage brake system
parts so badly that they'll have to be replaced.
Don't let someone put in the wrong kind of fluid.
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If you spill brake fluid on your vehicle's painted
surfaces, the paint finish can be damaged. Be
careful not to spill brake fluid on your vehicle. If
you do, wash it off immediately. See
"Appearance Care'' in the Index.
Brake Wear
Your vehicle has four-wheel disc brakes.
Disc brake pads have built-in wear indicators that make
a high-pitched warning sound when the brake pads
are worn and new pads are needed. The sound
may come and go or be heard all the time your vehicle
is moving (except when you are pushing on the
brake pedal firmly).
The brake wear warning sound means that
soon your brakes won't work well. That could
lead to an accident. When you hear the brake
wear warning sound, have your vehicle
serviced.
Notice: Continuing to drive with worn-out brake
pads could result in costly brake repair.
Some driving conditions or climates may cause a brake
squeal when the brakes are first applied or lightly
applied. This does not mean something is wrong with
your brakes.
Properly torqued wheel nuts are necessary to help
prevent brake pulsation. When tires are rotated, inspect
brake pads for wear and evenly tighten wheel nuts in
the proper sequence to GM torque specifications.
Brake linings should always be replaced as complete
axle sets.
See Brake System Inspection on page 6-15.
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