Subaru 2009 IMPREZA, Service Manual

Page: 2602 / 3619

BR-35
Brake Booster
BRAKE
• AIR TIGHTNESS CHECK
1) Start the engine and keep it running until vacu-
um pressure indicates point A of the vacuum gauge
= 66.7 kPa (500 mmHg, 19.69 inHg). Do not de-
press the brake pedal at this time.
2) Stop the engine and check the gauge. If the vac-
uum pressure drop within 15 seconds after stop-
ping the engine is 3.3 kPa (25 mmHg, 0.98 inHg) or
less, the function of brake booster is normal.
If faulty, the cause may be one of the following.
• Check valve malfunction
• Leak from vacuum hose
• Leak from shell joint section or stud bolt welded
section
• Damaged diaphragm
• Leak from valve body seal and bearing section
• Leak from plate and seal assembly section
• Leak from poppet valve assembly section
• LOADED AIR TIGHTNESS CHECK
1) Start the engine and depress the brake pedal
with a pedal force of 196 N (20 kgf, 44 lbf). Keep
the engine running and keep the pedal pressed
until a vacuum of point B = 66.7 kPa (500 mmHg,
19.69 inHg) is indicated on the vacuum gauge.
2) Stop the engine and check the vacuum gauge.
If the vacuum pressure drop within 15 seconds
after stopping the engine is 3.3 kPa (25 mmHg,
0.98 inHg) or less, the function of brake booster
is normal.
If defective, refer to “AIR TIGHTNESS CHECK”.
<Ref. to BR-33, INSPECTION, Brake Booster.>
3) If the brake booster is faulty, replace it with a
new part.
• LACK OF BOOST ACTION CHECK
Turn the engine OFF, and set the value of the vac-
uum gauge to “0”. Then, check the fluid pressure
when the brake pedal is depressed. The pressure
must be greater than the specification listed.
• BOOSTING ACTION CHECK
Set the vacuum gauge reading to 66.7 kPa
(500 mmHg, 19.69 inHg) with the engine running.
Then, check the fluid pressure when the brake
pedal is depressed. The pressure must be greater
than the specification listed.
(1) Pressure gauge
(2) Vacuum gauge
(1) Pressure gauge
(2) Vacuum gauge
(3) Pedal force gauge
(4) Depressed
BR-00083
(1) (2)
A
BR-00084
B
(1) (2)
(3)
(4)
Brake pedal operation
force
N (kgf, lbf)
147 (15, 33) 294 (30, 66)
Fluid pressure
kPa (kgf/cm
2
, psi)
545
(6, 79)
1,564
(16, 227)
Brake pedal operation
force
N (kgf, lbf)
147 (15, 33) 294 (30, 66)
Fluid pressure
kPa (kgf/cm
2
, psi)
6,003
(61, 871)
11,273
(115, 1,635)