Porsche Cayenne 2009 Owner's Manual page 166

Brake booster
The brake booster assists braking only when
the engine is running.
When the car is moving while the engine is not
running, or if the brake booster is defective, more
pressure on the brake pedal is required to bring
the car to a stop.
Moisture, road salt or grit on brakes affects
braking. When the vehicle is driven on salted or
sanded roads for extended periods, the brakes
should be washed down thoroughly about every
2 weeks. An automatic carwash facility cannot do
this job properly. Brakes will dry after a few
cautious brake applications.
Warning!
Risk of an accident, resulting in serious per-
sonal injury or death.
Driving through water may reduce the trac-
tion. Moisture on brakes from road water, car
wash, or a coating of road salt or grit may
affect braking efficiency.
f Cautiously apply brakes to test brakes after
exposure to road water, etc.
166
Driving and Driving Safety
Brake wear
Your car has excellent brakes, but they are still
subject to wear. The rate at which they wear
depends on how the brakes are used.
f Have the brake system inspected at the inter-
vals recommended in your Maintenance Book-
let.
Brake system warning light
You can check the functionality of the brake sys-
tem warning light by switching the ignition to the
"On" position and verifying that the warning light
illuminates.
Brake wear warning message
A warning message will be displayed on the multi-
purpose display of the instrument panel if the
brake pads are worn, excessively.
f Do not continue to operate the vehicle.
Have your authorized Porsche dealer inspect
or replace the brake pads.
f Please see the chapter "OVERVIEW OF
WARNING MESSAGES" on Page 149.
Brake pads and brake discs
Wear on the brake pads and brake discs depends
to a great extent on the driving style and the con-
ditions of use and therefore cannot be expressed
in actual miles on the road.
The high-performance brake system is designed
for optimal braking effect at all speeds and tem-
peratures.
Certain speeds, braking forces and ambient
conditions (such as temperature and humidity)
therefore might cause the brakes to squeal.