Chevrolet 2007 HH7 Owner's Manual page 318

So, it is not a good idea to top off your brake fluid.
Adding brake fluid will not correct a leak. If you
add fluid when your linings are worn, then you will
have too much fluid when you get new brake
linings. You should add or remove brake fluid, as
necessary, only when work is done on the
brake hydraulic system.
CAUTION:
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If your vehicle has too much brake fluid, it
can spill on the engine. The fluid will burn
if the engine is hot enough. You or others
could be burned, and your vehicle could
be damaged. Add brake fluid only when
work is done on the brake hydraulic
system.
When your brake fluid falls to a low level, your
brake warning light will come on. See Brake
System Warning Light on page 185.
318
Brake Wear
Your vehicle has front disc brakes and rear drum
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.
CAUTION:
{
The brake wear warning sound means that
soon the brakes will not 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.