Subaru WRX & WRX STI Manuals 2015 WRX & WRX STI Owner's Manual | Page 439

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Maintenance and service/Brake booster

Check the fluid level monthly.
Check the fluid level on the outside of the
reservoir. Because this reservoir is used
for both the brake and clutch systems and
has chambers for each system, be sure to
check the fluid level for the clutch system
at the inboard side of the reservoir
(shaded area in the illustration). If the fluid
level is below “MIN”, add the recommended clutch fluid to “MAX”.
Use only clutch fluid from a sealed
container.

& Recommended clutch fluid
Refer to “Fluids” F12-7.

CAUTION
Never use different brands of clutch
fluid together. Also, avoid mixing
DOT 3 and DOT 4 brake fluids even if
they are the same brand.

Brake booster
If the brake booster does not operate as
described in the following, 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 one 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 lighter depression of the brake
pedal generates a greater braking
force. However, even though these
occur, they do 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.