Brake Booster - Subaru WRX-STI Owner's Manual

11-30
Maintenance and service/Brake booster
NOTE
The fluid level for the clutch system
must be checked at the inboard side of
the reservoir. It cannot be checked at
the outboard side of the reservoir.

Brake booster

If the brake booster does not operate as
described in the following, we recommend
that you have it checked by your SUBARU
dealer.
1. With the engine off, depress the brake
pedal several times, applying the same
pedal force each time. The distance the
pedal travels should not vary.
2. With the brake pedal depressed, start
the engine. The pedal should move
slightly down to the floor.
3. With the brake pedal depressed, stop
the engine and keep the pedal depressed
for 30 seconds. The pedal height should
not change.
4. Start the engine again and run for
approximately 1 minute then turn it off.
Depress the brake pedal several times to
check the brake booster. The brake
booster operates properly if the pedal
stroke decreases with each depression.
NOTE
When you depress the brake pedal
strongly or suddenly, you might feel
that the brake pedal is applied by
lighter force and generates a greater
braking force. However, even though
this occurs, it does not indicate any
malfunctions, and the brake assist
system is operating properly.
Brake assist is not a system that brings
more braking ability to the vehicle
beyond its breaking capability.