Subaru Impreza 2004 Service Manual page 58

• Air tightness check
Start the engine, and run it for 1 to 2 minutes, then
turn it off. Depress the brake pedal several times
applying same pedal force as that used in ordinary
braking operations. The pedal stroke should be
greatest on 1st depression, and it should become
smaller with each successive depression. If no
change occurs in the pedal height while in a de-
pressed state, the brake booster is faulty.
(1)
(5)
(4)
(3)
(1) OK
(2) NOT OK
(3) 1st
(4) 2nd
(5) 3rd
NOTE:
• In the event of defective operation, inspect the
condition of check valve and vacuum hose.
• Replace them if faulty and conduct the test
again.
• If no improvement is observed, check precisely
with gauges.
• Operation check
1) With the engine off, depress the brake pedal
several times applying same pedal force and make
sure that pedal height does not vary with each de-
pression of pedal.
(1)
(1) When engine is stopped
(2) When engine is started
2) With the brake pedal depressed, start the en-
gine.
Brake Booster
(2)
BR-00080
(2)
BR-00081
BR-57
3) As the engine starts, the brake pedal should
move slightly toward the floor. If no change occurs
in the pedal height, the brake booster is faulty.
NOTE:
If faulty, check precisely with gauges.
• Loaded air tightness check
Depress the brake pedal while engine is running,
and turn off the engine while pedal is still de-
pressed. Keep the pedal depressed for 30 sec-
onds; if no change occurs in the pedal height, the
brake booster is functioning normally; if the pedal
height increases, it is faulty.
NOTE:
If faulty, check precisely with gauges.
2. OPERATION CHECK (WITH GAUGES)
CAUTION:
When checking operation, be sure to securely
apply the parking brake.
• Checking with gauges
Connect gauges as shown in the figure. After
bleeding air from pressure gauges, proceed to
each check.
(1) (2)
(3)
(1) Pressure gauge
(2) Vacuum gauge
(3) Adapter hose
(4) Vacuum hose
(5) Pedal force gauge
BRAKE
(4) (5)
BR-00082