1996 SUBARU LEGACY brake

19. Air Bleeding (With TCS model)
A: RULES FOR EFFECTIVE BLEEDING
1) Pressure is not applied to suction pipe by depressing
brake pedal. When any of the following are performed,
bleed air from suction pipe by air bleeding control opera-
tion.
NOTE:
For TCS vehicle, suction pipe is installed between master
cylinder and hydraulic unit to allow flow of brake fluid
between them during ABS and TCS operation.
(1) When brake pipe is disconnected from master cyl-
inder.
(2) When brake pipe between hydraulic unit and mas-
ter cylinder is disconnected.
(3) When fluid is emptied from reservoir tank.
2) The time interval between two brake pedal operations
(from the time when the pedal is released to the time when
it is depressed another time) shall be approximately 3 sec-
onds.
3) The air bleeder on each brake shall be released for 1
to 2 seconds.
B: BLEEDING PROCEDURE WITH AIR
BLEEDING CONTROL
1. BLEEDING PROCEDURE
CAUTION:

The FMVSS No. 116, fresh DOT3 or 4 brake fluid
must be used.

Cover bleeder with waste cloth, when loosening it,
to prevent brake fluid from being splashed over sur-
rounding parts.

Avoid mixing different brands of brake fluid to pre-
vent degrading the quality of the fluid.

Be careful not to allow dirt or dust to get into the
reservoir tank.

During bleeding operation, keep the brake reserve
tank filled with brake fluid to eliminate entry of air.
NOTE:

Brake pedal operating must be very slow.

For convenience and safety, it is advisable to have two
man working.
G4M0434
1) Start air bleeding control operation. [W19C0] or [W19D0].>
2) Make sure that there is no leak from joints and connec-
tions of the brake system.
3) Bleed air through front RH caliper by operating brake
pedal.
(1) Fit one end of vinyl tube into the air bleeder and put
the other end into a brake fluid container.
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19. Air Bleeding (With TCS model)

(2) Slowly depress the brake pedal and keep it
depressed. Then, open the air bleeder to discharge air
together with the fluid.
Release air bleeder for 1 to 2 seconds.
Next, with the bleeder closed, slowly release the brake
pedal.
Repeat these steps until there are no more air bubbles
in the vinyl tube.
Allow 3 to 4 seconds between two brake pedal opera-
tions.
CAUTION:
Cover bleeder with waste cloth, when loosening it, to
prevent brake fluid from being splashed over sur-
rounding parts.
NOTE:
Brake pedal operating must be very slow.
4) Bleed air from suction pipe through front RH caliper.
(1) Open the air bleeder.
(2) Keep pressing TCS OFF switch for 20 seconds or
more.
NOTE:
Ensure no air comes out from air bleeder.
(3) Close the air bleeder.
5) Bleed air through front LH caliper by operating brake
pedal. This is the same procedure as step 3).
6) Bleed air from suction pipe through front LH caliper.
This is the same procedure as step 4).
7) Bleed air through front RH and LH calipers by operat-
ing brake pedal. This is the same procedure as step 3).
Repeat steps 3) to 7) until air does no longer comes out.
8) Tighten air bleeders securely when bubbles are visible.
Air bleeder tightening torque:
8±1 N⋅m (0.8±0.1 kg-m, 5.8±0.7 ft-lb)
9) Bleed air through rear LH and RH caliper by operating
brake pedal. This is the same procedure as step 3).
10) Tighten air bleeders securely when bubbles are vis-
ible.
Air bleeder tightening torque:
8±1 N⋅m (0.8±0.1 kg-m, 5.8±0.7 ft-lb)
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19. Air Bleeding (With TCS model)

11) Operate FRO (Front Right Outlet) valve and RLO
(Rear Left Outlet) valve to bleed air from hydraulic unit
outlet circuit.
(1) Press TCS OFF switch while depressing brake
pedal.
(2) Make sure ABS warning light illuminates.
(3) Repeatedly depress and release brake pedal 10
times or more while pressing TCS OFF switch.
NOTE:

Air comes out from reservoir tank.
12) Operate FLO (Front Left Outlet) valve and RRO (Rear
Right Outlet) valve to bleed air from hydraulic unit outlet
circuit.
(1) Press TCS OFF switch while depressing brake
pedal.
(2) Make sure TCS warning light illuminates.
(3) Repeatedly depress and release brake pedal 10
times or more while pressing TCS OFF switch.
NOTE:

Air comes out from reservoir tank.

The operations in steps 11) and 12) above can be
switched with each other by operating brake pedal (stop
light switch) while pressing TCS OFF switch.

Repeat procedures 11) and 12) until air no longer comes
out of reservoir tank.
13) Perform these steps for the brakes connecting to the
secondary chamber of master cylinder, first, and then for
the ones connecting to primary chamber. With all proce-
dures completed, fully depress the brake pedal and keep
it in that position for approximately 20 seconds to make
sure that there is no leak evident in the entire system.
14) Turn ignition switch OFF.
15) Perform TCS sequence control. [W20F0].>
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19. Air Bleeding (With TCS model)

G4M0436
16) Check the pedal stroke.
While the engine is idling, depress the brake pedal with a
490 N (50 kg, 110 lb) load and measure the distance
between the brake pedal and steering wheel. With the
brake pedal released, measure the distance between the
pedal and steering wheel again. The difference between
the two measurements must be less than specified.
Specified pedal stroke:
With TCS
95 mm (3.74 in)
When depressing brake pedal with a 490 N (50 kg,
110 lb) load.
If the distance is more than specifications, there is a
possibility that air is in the brake line. Bleed air from the
brake line.
17) Turn ignition switch OFF.
18) Disconnect select monitor or diagnosis terminal.
19) Add brake fluid to the required level (MAX. level) of
reserve tank.
20) As a final step, test run the vehicle at low speed and
apply brakes relatively hard 2 to 3 times to ensure that
brakes provide normal braking action on all four wheels
without dragging and uneven braking.
2. CONDITIONS FOR AIR BLEEDING CONTROL
Stop light
switchTCS OFF
switchPump
motorTCS
valveFRO
RLOFLO
RROTCS
operating
indicator
lightABS
warning
lightTCS
warning
light
Air
bleeding
control is
operating.OFF ON ON Close Close Close ON ON ON
ON ON OFF Open Open Close ON ON OFF
ON ON OFF Open Close Open ON OFF ON
ON or OFF OFF OFF Open Close Close ON OFF OFF
Stops tem-
porarily.*——OFF Open Close Close OFF OFF OFF
Prohibited.——OFF Open Close Close OFF ON ON
*: When brake fluid level switch detects brake fluid in LOW level, control operation stops temporarily. After refilling brake fluid, operation
re-starts.
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19. Air Bleeding (With TCS model)

3. CONDITIONS FOR COMPLETION OF AIR
BLEEDING CONTROL
When any of the following conditions occurs, ABS and TCS
warning lights illuminate. Air bleeding control stops, while
the ABS and TCS function will then stop. The brake sys-
tem functions as a conventional brake system.
1) When the speed of at least one wheel reaches 10 km/h
(6 MPH).
2) When terminal No. 4 is separated from diagnosis termi-
nal. (When select monitor is not used.)
3) When pump motor remains ON for two minutes.
4) When TCS valve remains open for two minutes.
5) When outlet valve remains closed for two minutes.
6) When malfunction is detected.
NOTE:
When a malfunction is detected the air bleeding operation
stops and the trouble codes are stored in memory.
B4M0082C
C: AIR BLEEDING CONTROL WITH
DIAGNOSIS CONNECTOR
1) Connect diagnosis terminals to terminal No. 4 of the
diagnosis connector beside driver’s seat heater unit.
B4M0621A
2) Start the engine while pushing TCS OFF switch.
NOTE:
Keep the TCS OFF switch depressed even after the engine
has started.
3) After ABS and TCS warning lights go out, depress
brake pedal within 0.5 seconds.
4) After ensuring TCS ON indicator illuminates, release
TCS OFF switch and brake pedal.
5) Air bleeding control operation starts.
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19. Air Bleeding (With TCS model)

20. Hydraulic Unit for ABS/TCS System
B4M0707A
1ABS/TCS hydraulic
control unit

2Rear-RH outlet

3Front-LH outlet

4Front-RH outlet

5Rear-LH outlet

6Secondary inlet

7Primary inlet
8Secondary suction line

9Primary suction line

10Bumper

11Bracket

12Pressure switch

13Valve relay

14Motor relay
Tightening torque: N⋅m (kg-m, ft-lb)
T1: 7.4±2.0 (0.75±0.2, 5.4±1.4)
T2: 29±7 (3.0±0.7, 21.7±5.1)
T3: 32±10 (3.3±1.0, 24±7)
T4: 38±10 (3.8±1.0, 27±7)
T5: 3.1±1 (0.32±0.1, 2.3±0.7)
A: REMOVAL
1) Disconnect ground cable from battery.
2) Remove canister, air intake and air cleaner case duct
from engine compartment to facilitate removal of hydraulic
unit.
3) Disconnect brake pipes from hydraulic unit.
CAUTION:
Wrap brake pipes with vinyl bag to avoid spilling brake
fluid on vehicle body.
4) Disconnect connector from hydraulic unit.
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20. Hydraulic Unit for ABS/TCS System

C: CHECKING THE HYDRAULIC UNIT ABS
OPERATION
1. CHECKING THE HYDRAULIC UNIT ABS
OPERATION BY PRESSURE GAUGE
1) Lift-up vehicle and remove wheels.
2) Disconnect the air bleeder screws from the FL and FR
caliper bodies.
B4M0633A
3) Connect two pressure gauges to the FL and FR caliper
bodies.
CAUTION:

Pressure gauges used exclusively for brake fluid
must be used.

Do not employ pressure gauge previously used for
transmission since the piston seal is expanded which
may lead to malfunction of the brake.
NOTE:
Wrap sealing tape around the pressure gauge.
4) Bleed air from the pressure gauges.
5) Perform ABS sequence control.
6) When the hydraulic unit begins to work, and first the FL
side performs decompression, holding, and compression,
and then the FR side performs decompression, holding,
and compression.
7) Read values indicated on the pressure gauge and
check if the fluctuation of the values between decompres-
sion and compression meets the standard values. Also
check if any irregular brake pedal tightness is felt.
Initial value When decompressed When compressed
Front wheel 3,432 kPa (35 kg/cm
2, 498 psi)490 kPa (5 kg/cm2, 71 psi)
or less981 kPa (10 kg/cm2, 142 psi)
or more
Rear wheel 3,432 kPa (35 kg/cm
2, 498 psi)490 kPa (5 kg/cm2, 71 psi) or
less981 kPa (10 kg/cm2, 142 psi)
or more
8) Remove pressure gauges and air bleeder screws from
the RL and RR caliper bodies.
9) Connect the air bleeder screws hose to the FL and FR
caliper bodies.
10) Connect two pressure gauges to the RL and RR cali-
per bodies.
11) Bleed air from the pressure gauges and the FL and FR
caliper bodies.
12) Perform ABS sequence control. [W20D0].>
13) When the hydraulic unit begins to work, at first the RR
side performs decompression, holding, and compression,
and then the RL side performs decompression, holding,
and compression.
14) Read values indicated on the pressure gauges and
check if they meet the standard value.
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20. Hydraulic Unit for ABS/TCS System

15) After checking, remove the pressure gauges from cali-
per bodies.
16) Connect the air bleeder screws to RL and RR caliper
bodies.
17) Bleed air from brake line.
2. CHECKING THE HYDRAULIC UNIT ABS
OPERATION WITH BRAKE TESTER
1) Prepare for operating ABS sequence control. 4-4 [W20D1] or 4-4 [W20D2].>
G4M0464
2) Set the front wheels or rear wheels on the brake tester
and set the select lever’s position at“neutral”.
3) Operate the brake tester.
4) Perform ABS sequence control. step 1 or 4-4 [W20D2] step 1.>
5) Hydraulic unit begins to work; and check the following
working sequence.
(1) The front left wheel performs decompression,
holding, and compression in sequence, and subse-
quently the front right wheel repeats the cycle.
(2) The rear right wheel performs decompression,
holding, and compression in sequence, and subse-
quently the rear left wheel repeats the cycle.
6) Read values indicated on the brake tester and check if
the fluctuation of values, when decompressed and
compressed, meet the standard values.
Unit: N (kg, lb)
Initial value When decompressed When compressed
Front wheel981—1,471
(100—150, 221—331)245 (25, 55) or less 588 (60, 132) or more
Rear wheel981—1,471
(100—150, 221—331)245 (25, 55) or less 588 (60, 132) or more
7) After checking, also check if any irregular brake pedal
tightness is felt.
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20. Hydraulic Unit for ABS/TCS System