GMC 1996 Sierra Owner's Manual page 285

NOTICE:
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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.
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
If you have a C 3500
HD
model, it 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).
A'
CAUTION:
I
The brake wear warning sound means that
sooner or later your brakes won't work well.
That could lead to an accident. When you hear
the brake wear warning sound, have your
vehicle serviced.
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