Subaru Impreza 2003, Service Manual

Page: 2590 / 3610

BR-58
BRAKE
BRAKE BOOSTER
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.
• Air tightness check
1) Start the engine and keep it running until a vac-
uum of 66.7 kPa (500 mmHg, 19.69 inHg) = point A
is indicated on vacuum gauge. Do not depress the
brake pedal.
2) Stop the engine and watch the gauge. If the vac-
uum drop range is less than 3.3 kPa (25 mmHg,
0.98 inHg) within 15 seconds after stopping engine,
the 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
• Damaged diaphragm
• Leak from valve body seal and bearing portion
• Leak from plate and seal assembly portion
• Leak from poppet valve assembly portion
• Loaded air tightness check
1) Start the engine and depress brake pedal with
pedal force of 196 N (20 kgf, 44 lb). Keep the en-
gine running until a vacuum of 66.7 kPa (500
mmHg, 19.69 inHg) = point B is indicated on vacu-
um gauge while the pedal is still depressed.
2) Stop the engine and watch vacuum gauge.
If the vacuum drop range is less than 3.3 kPa (25
mmHg, 0.98 inHg) within 15 seconds after stopping
engine, the brake booster is functioning properly.
If defective, refer to “AIR TIGHTNESS CHECK”.
<Ref. to BR-57, INSPECTION, Brake Booster.>
3) If any fault is found on brake booster, replace the
brake booster with a new one.
(1) Pressure gauge
(2) Vacuum gauge
(3) Adapter hose
(4) Vacuum hose
(5) Pedal force gauge
(1) Pressure gauge
(2) Vacuum gauge
(1) (2)
(3) (4) (5)
BR-00082
(1) (2)
A
BR-00083
(1) Pressure gauge
(2) Vacuum gauge
(3) Pedal force gauge
(4) Depress
B
(1) (2)
(3)
(4)
BR-00084