Subaru Legacy III (2000-2003 year). Manual — part 736

VDC-12

VDC

HYDRAULIC CONTROL UNIT (H/U)

C: INSPECTION

1) Check connected and fixed condition of connector.
2) Check valve relay and motor relay for discontinuity or short circuits.

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.
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.
<Ref. to VDC-16, 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 de-
compression, holding, and compression.

Condition

Terminal number

Standard

Diagram

Terminal location

Valve
relay

Turning off elec-
tricity.

85 — 86

103

±

10

Ω

30 — 87a

Less than 0.5

Ω

30 — 87

More than 1 M

Ω

Turning on elec-
tricity between 85
and 86. (DC 12 V)

30 — 87a

More than 1 M

Ω

30 — 87

Less than 0.5

Ω

Motor
relay

Turning off elec-
tricity.

85 — 86

80

±

10

Ω

30 — 87

More than 1 M

Ω

Turning on elec-
tricity between 85
and 86. (DC 12 V)

30 — 87

Less than 0.5

Ω

VDC00082

87

85

86

30

87a

VDC00083

87

87a

30

86

85

VDC00084

87

85

86

30

VDC00085

87

85

86

30

ABS00134

VDC-13

VDC

HYDRAULIC CONTROL UNIT (H/U)

7) Read values indicated on the pressure gauge
and check if the fluctuation of the values between
decompression and compression meets the stan-
dard values. Also check if any irregular brake pedal
tightness is felt.

8) Remove pressure gauges from FL and FR cali-
per bodies.
9) Remove air bleeder screws from the RL and RR
caliper bodies.
10) Connect the air bleeder screws to the FL and
FR caliper bodies.
11) Connect two pressure gauges to the RL and
RR caliper bodies.
12) Bleed air from the pressure gauges and the FL
and FR caliper bodies.
13) Perform ABS sequence control.
<Ref. to VDC-16, ABS Sequence Control.>
14) When the hydraulic unit begins to work, at first
the RR side performs decompression, holding, and
compression, and then the RL side performs de-
compression, holding, and compression.
15) Read values indicated on the pressure gauges
and check if they meet the standard values.
16) After checking, remove the pressure gauges
from caliper bodies.
17) Connect the air bleeder screws to RL and RR
caliper bodies.
18) Bleed air from brake line.

2. CHECKING THE HYDRAULIC UNIT ABS
OPERATION WITH BRAKE TESTER

1) Prepare for operating ABS sequence control.
<Ref. to VDC-16, ABS Sequence Control.>
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.
<Ref. to VDC-16, ABS Sequence Control.>
5) When the hydraulic unit begins to work, check
the following working sequence.

(1) The FL wheel performs decompression,
holding, and compression in sequence, and
subsequently the FR wheel repeats the cycle.
(2) The RR wheel performs decompression,
holding, and compression in sequence, and
subsequently the RL wheel repeats the cycle.

Front wheel

Rear wheel

Initial value

3,432 kPa

(35 kg/cm

2

, 498 psi)

3,432 kPa

(35 kg/cm

2

, 498 psi)

When
decom-
pressed

490 kPa

(5 kg/cm

2

, 71 psi)

or less

490 kPa

(5 kg/cm

2

, 71 psi)

or less

When
compressed

3,432 kPa

(35 kg/cm

2

, 498 psi)

or more

3,432 kPa

(35 kg/cm

2

, 498 psi)

or more

(1) Brake tester

(1) Brake tester

( 1 )

ABS00136

( 1 )

ABS00137

VDC-14

VDC

HYDRAULIC CONTROL UNIT (H/U)

6) Read values indicated on the brake tester and
check if the fluctuation of values, when decom-
pressed and compressed, meet the standard val-
ues.

7) After checking, also check if any irregular brake
pedal tightness is felt.

3. CHECKING THE HYDRAULIC UNIT VDC
OPERATION BY PRESSURE GAUGE

1) Lift-up vehicle and remove wheels.
2) Disconnect the air bleeder screws from the FL
and FR caliper bodies.
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 VDC sequence control.
<Ref. to VDC-19, VDC 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 de-
compression, holding, and compression.

7) Read values indicated on the pressure gauge
and check if the fluctuation of the values between
decompression and compression meets the stan-
dard values. Also check if any irregular brake pedal
tightness is felt.

8) Remove pressure gauges from FL and FR cali-
per bodies.
9) Remove air bleeder screws from the RL and RR
caliper bodies.
10) Connect the air bleeder screws to the FL and
FR caliper bodies.
11) Connect two pressure gauges to the RL and
RR caliper bodies.
12) Bleed air from the pressure gauges and the FL
and FR caliper bodies.
13) Perform VDC sequence control.
<Ref. to VDC-19, VDC Sequence Control.>
14) When the hydraulic unit begins to work, at first
the RR side performs decompression, holding, and
compression, and then the RL side performs de-
compression, holding, and compression.
15) Read values indicated on the pressure gauges
and check if they meet the standard value.
16) After checking, remove the pressure gauges
from caliper bodies.
17) Connect the air bleeder screws to RL and RR
caliper bodies.
18) Bleed air from brake line.

Front wheel

Rear wheel

Initial value

981 N

(100 kgf, 221 lb)

981 N

(100 kgf, 221 lb)

When
decompressed

490 N

(50 kgf, 110 lb)

or less

490 N

(50 kgf, 110 lb)

or less

When
compressed

981 N

(100 kgf, 221 lb)

or more

981 N

(100 kgf, 221 lb)

or more

ABS00134

Front wheel

Rear wheel

When
compressed

2,942 kPa

(30 kg/cm

2

, 427 psi)

or more

1,961 kPa

(20 kg/cm

2

, 284 psi)

or more

When
decom-
pressed

490 kPa

(5 kg/cm

2

, 71 psi)

or less

490 kPa

(5 kg/cm

2

, 71 psi)

or less

VDC-15

VDC

HYDRAULIC CONTROL UNIT (H/U)

4. CHECKING THE HYDRAULIC UNIT VDC
OPERATION WITH BRAKE TESTER

1) Prepare for operating VDC sequence control.
<Ref. to VDC-19, VDC Sequence Control.>
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.
<Ref. to VDC-16, ABS Sequence Control.>
5) When the hydraulic unit begins to work, check
the following working sequence.

(1) The FL wheel performs decompression,
holding, and compression in sequence, and
subsequently the FR wheel repeats the cycle.
(2) The RR wheel performs decompression,
holding, and compression in sequence, and
subsequently the RL wheel repeats the cycle.

6) Read values indicated on the brake tester and
check if the fluctuation of values, when decom-
pressed and compressed, meet the standard val-
ues.

7) After checking, also check if any irregular brake
pedal tightness is felt.

(1) Brake tester

(1) Brake tester

Front wheel

Rear wheel

When
compressed

1,961 N

(200 kgf, 441 lb)

or more

981 N

(100 kgf, 221 lb)

or more

When
decompressed

490 N

(50 kgf, 110 lb)

or less

490 N

(50 kgf, 110 lb)

or less

( 1 )

ABS00136

( 1 )

ABS00137