Subaru Impreza 2004 Service Manual page 59

BRAKE
• 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.
(1) (2)
(1) Pressure gauge
(2) Vacuum gauge
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.
(1) (2)
(1) Pressure gauge
(2) Vacuum gauge
(3) Pedal force gauge
(4) Depress
Brake Booster
A
BR-00083
B
(3)
(4)
BR-00084
BR-58
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-56, INSPECTION, Brake Booster.>
3) If any fault is found on brake booster, replace the
brake booster with a new one.
• Lack of boosting action check
Turn off the engine, and set the vacuum gauge
reading at "0". Then, check the fluid pressure when
brake pedal is depressed. The pressure must be
greater than the standard value listed.
Brake pedal 147 N
force (15 kgf, 33 lb)
686 kPa
(7 kg/cm
14"
[588 kPa (6 kg/
Fluid
2
cm , 85 psi)]
pressure
15"
588 kPa
16"
(6 kg/cm
17"
[ ] : Model with ABS
• Boosting action check
Set the vacuum gauge reading at 66.7 kPa (500
mmHg, 19.69 inHg) by running engine. Then,
check the fluid pressure when brake pedal is de-
pressed. The pressure must be greater than the
standard value listed.
Brake pedal 147 N
force (15 kgf, 33 lb)
5,982 kPa
14"
(61 kg/cm
psi)
5,296 kPa
15"
Fluid
(54 kg/cm
pressure psi)
4,707 kPa
16"
(48 kg/cm
psi)
4,021 kPa
17"
(41 kg/cm
psi)
[ ] : Model with ABS
294 N
(30 kgf, 66 lb)
1,961 kPa
2 2
, 100 psi) (20 kg/cm , 284 psi)
[1,667 kPa (17 kg/
2
cm , 242 psi)]
1,471 kPa
2 2
, 85 psi) (15 kg/cm , 213 psi)
294 N
(30 kgf, 66 lb)
7,649 kPa
2
(78 kg/cm , 1,109
2
psi)
, 868
[8,434 kPa (86 kg/
2
cm , 1,223 psi)]
2
, 768
9,120 kPa
2
(93 kg/cm , 1,323
psi)
2
, 683
8,336 kPa
2 2
, 583 (85 kg/cm , 1,209
psi)