Subaru Impreza 3 / Impreza WRX / Impreza WRX STI. Manual — part 562

BR-33

Master Cylinder

BRAKE

8. Master Cylinder

A: REMOVAL

CAUTION:

Do not allow brake fluid to come in contact with

the painted surface of the vehicle body. If it

does, wash off with water and wipe away com-

pletely.

1) Drain brake fluid from the reservoir tank com-

pletely.

2) Disconnect the harness connector of the fluid

level gauge.

3) Remove the brake pipe from the master cylinder.

4) Remove the master cylinder mounting nuts, and

carefully remove the master cylinder from the brake

booster.

B: INSTALLATION

1) Replace the O-ring for the master cylinder with a

new part.
CAUTION:

Be careful not to install the O-ring in the wrong

location.

2) Install each part in the reverse order of removal.
Tightening torque:

Master cylinder mounting nut

13 N·m (1.33 kgf-m, 9.6 ft-lb)

Piping flare nut

15 N·m (1.53 kgf-m, 11.1 ft-lb)

CAUTION:

Be sure to use recommended brake fluid. <Ref.

to BR-2, SPECIFICATION, General Descrip-

tion.>

3) Bleed air from the brake system. <Ref. to BR-41,

PROCEDURE, Air Bleeding.>

C: REPLACEMENT

1) Remove mud and dirt from the surface of brake

master cylinder.

2) Secure the master cylinder in a vise.
CAUTION:

To avoid damaging the master cylinder, place

between aluminum plates or other material

when holding with a vise.

3) Remove the pin which secures the master cylin-

der and reservoir tank, then remove the reservoir

tank and seal.

4) While pushing in the primary piston, remove the

C-ring using pliers.

5) While pushing in the primary piston, remove the

cylinder pin (1) from the port on the reservoir tank

attachment location using a magnet pick-up tool.

6) Extract the primary piston assembly and sec-

ondary piston assembly straight out while taking

care not to scratch the inner surface of the cylinder.

7) Clean the inside of master cylinder with brake

fluid. Check the inside of the cylinder for damage,

deformation and wear. Replace the master cylinder

as an assembly if faulty.

(1) Primary piston
(2) O-ring
(3) Do not install the O-ring on this groove.

BR-00363

(1)

(2)

(3)

BR-00364

BR-00169

BR-00069

(1)

BR-34

Master Cylinder

BRAKE

8) Apply brake fluid to the inner surface of master

cylinder and piston assembly.

9) Make sure that the inner surface of master cylin-

der and the piston assembly are free of foreign

matter. Install the primary piston assembly and the

secondary piston assembly to master cylinder,

while taking care not to scratch the master cylinder

inner surface.

10) While pushing-in the primary piston, install the

cylinder pin.

11) While pushing-in the primary piston, install the

C-ring to the groove using pliers.
CAUTION:

Make sure the C-ring is installed to the groove

securely.

12) Install the seal (1) to reservoir tank.

13) Install the reservoir tank to the master cylinder,

and secure with pin.

14) Replace the O-ring for the master cylinder with

a new part.

D: INSPECTION

Inspect for brake fluid leakage from the master cyl-

inder.
NOTE:

After replacing the piston kit, if an brake fluid leak-

age is found even though there is no damage or

scratches on the inside of the cylinder, the master

cylinder inner wall may be worn. In this case, re-

place the master cylinder as an assembly.

(1) Primary piston
(2) O-ring
(3) Do not install the O-ring on this groove.

BR-00169

BR-00072

(1)

BR-00363

(1)

(2)

(3)

BR-35

Brake Booster

BRAKE

9. Brake Booster

A: REMOVAL

1) Remove or disconnect the following parts in the

engine compartment.

(1) Disconnect the connector of brake fluid level

gauge.

(2) Remove the brake pipe from the master cyl-

inder.

(3) Remove the master cylinder installation nut.

(4) Disconnect the vacuum hose from brake

booster.

2) Remove the following parts from the pedal

bracket.

(1) Snap pin and clevis pin

(2) Four brake booster installation nuts

3) Remove the brake booster while avoiding the

brake pipe.
CAUTION:

• Do not disassemble the brake booster.

• If external force (1) is applied from above

when brake booster is placed in this position,

the resin portion as indicated by “P” may be-

come damaged.

NOTE:

• Make sure that the booster shell and vacuum

pipe are not subject to strong impacts.

• Be careful not to drop the brake booster. If the

booster is dropped, replace it.

• Use special care when handling the operating

rod. If excessive force is applied to the operating

rod, the angle may change by ±3°, and it may result

in damage to power piston cylinder.

• Be careful when placing the brake booster on

floor.

• Do not change the push rod length.

B: INSTALLATION

1) Check and adjust the operating rod of the brake

booster.
Specification L:

136.3 mm (5.37 in)

If it is out of specification, adjust it with the brake

booster operating rod.

(1) Nut
(2) Clevis pin
(3) Snap pin
(4) Operating rod
(5) Brake pedal

(2)

(4)

(5)

(3)

BR-00685

(1)

(1)

P

BR-00075

BR-00076

L

BR-36

Brake Booster

BRAKE

2) Mount the brake booster in position.

3) Install clevis pin and snap pin which secure the

operating rod to the brake pedal.

NOTE:

• Replace with a new clevis pin.

• Apply NIGTIGHT LYW No. 2 grease to the clevis

pin.

4) Connect the vacuum hose to the brake booster.

5) After replacing the O-ring, install the master cyl-

inder to brake booster.

6) Connect the brake pipes to the master cylinder.

7) Connect the connector of the brake fluid level

gauge.

8) Apply grease to the operating rod connecting pin

to prevent it from wear.

9) Bleed air from the brake system. <Ref. to BR-41,

PROCEDURE, Air Bleeding.>

10) Perform a road test to make sure the brakes do

not drag.

C: INSPECTION

NOTE:

On the model with brake assist mechanism, the fol-

lowing phenomena occur when the brake pedal is

depressed. However, those are not malfunction but

the phenomena that occur when the brake assist

mechanism functions properly.

• Brake feel is soft when brake pedal is depressed

hard or quicker than usual.

• ABS operating sound is heard when brake pedal

is depressed hard or quicker than usual.

(1) Nut
(2) Clevis pin
(3) Snap pin
(4) Operating rod
(5) Brake pedal

(2)

(4)

(5)

(3)

BR-00685

(1)

(1) Primary piston
(2) O-ring
(3) Do not install the O-ring on this groove.

BR-00363

(1)

(2)

(3)