Subaru LEGACY Service Manual page 38

BRAKE
• Operation check
1) With engine off, depress brake pedal several
times applying the same pedal force and make
sure that the pedal height does not vary with each
depression of the pedal.
( 1 )
(1) When engine is stopped
(2) When engine is started
2) With brake pedal depressed, start engine.
3) As engine starts, brake pedal should move
slightly toward the floor. If no change occurs in the
pedal height, brake booster is faulty.
NOTE:
If faulty, check precisely with gauges.
• Loaded air tightness check
Depress brake pedal while engine is running, and
turn off engine while the pedal is still depressed.
Keep the pedal depressed for 30 seconds; if no
change occurs in the pedal height, brake booster is
functioning normally; if the pedal height increases,
it is faulty.
NOTE:
If faulty, check precisely with gauges.
BRAKE BOOSTER
2. OPERATION CHECK (WITH GAUGES)
CAUTION:
When checking operation, be sure to securely
apply the hand brake.
• Checking with gauges
Connect gauges as shown in Figure. After bleeding
( 2 )
air from pressure gauges, proceed to each check.
BR-00081
• Air tightness check
1) Start engine and keep it running until a vacuum
of 66.7 kPa (500 mmHg, 19.69 inHg) = point A is in-
dicated on vacuum gauge. Do not depress brake
pedal.
2) Stop engine and watch the gauge. If the vacuum
drop range is less than 3.3 kPa (25 mmHg, 0.98 in-
Hg) within 15 seconds after stopping engine, brake
booster is functioning properly.
If defective, the cause may be one of those listed
below.
• Check valve malfunction
• Leak from vacuum hose
• Leak from the shell jointed portion or stud bolt
welded portion
BR-36
( 1 ) ( 2 )
( 3 ) ( 4 )
(1) Pressure gauge
(2) Vacuum gauge
(3) Adapter hose
(4) Vacuum hose
(5) Pedal force gauge
( 1 ) ( 2 )
A
(1) Pressure gauge
(2) Vacuum gauge
( 5 )
BR-00082
BR-00083