Honda Civic manuals

Subaru Legacy Service Manual: Inspection

1. OPERATION CHECK WHEN NOT USING MEASURING DEVICES

CAUTION:

When checking operation, be sure to apply the parking brake securely.

When an operation check is performed with no measuring devices, a faulty part cannot be identified correctly. But it is possible to identify the outline of the defect by performing the check according to the following procedures.

Air tightness check

1. Start the engine, and idle it for 1 to 2 minutes, then turn it OFF.

2. Depress the brake pedal several times applying the normal pedal force.

NOTE:

The pedal stroke should be the longest at the 1st depression, and it should become shorter at each successive depression.

3. If no change occurs in the pedal height when pressed, the vacuum booster assembly is faulty.

(A)

Normal

(B)

Not OK

(a)

1st

(b)

2nd

(c)

3rd

NOTE:

In case of defective operation, inspect the condition of the check valve and vacuum hose as well.

Replace them if faulty, and perform the test again.

If no improvement is observed, check precisely with gauges.

Check operation

1. While the engine is OFF, depress the brake pedal several times applying the same pedal force, to check for a change in pedal height.

(a)

When engine is stopped

(b)

When engine is started

2. With the brake pedal depressed, start the engine.

3. As the engine starts, the brake pedal should move slowly toward the floor. If the pedal height does not change, the vacuum booster assembly is faulty.

NOTE:

If a faulty part is detected after inspection, check precisely with measuring devices.

Loaded air tightness check

Depress the brake pedal while the engine is running, and turn the engine to OFF while the pedal is depressed.

Keep the pedal depressed for 30 seconds. If the pedal height does not change, the function of vacuum booster assembly is normal. If the pedal height increases, it is faulty.

NOTE:

If a faulty part is detected after inspection, check precisely with measuring devices.

2. OPERATION CHECK WHEN USING MEASURING DEVICES

CAUTION:

When checking operation, be sure to apply the parking brake securely.

Check with measuring devices

Connect a measuring device as shown in the figure. After bleeding air from the pressure gauge, perform each check.

(a)

Pressure gauge

(c)

Adapter hose

(e)

Pedal force gauge

(b)

Vacuum gauge

(d)

Vacuum hose

Air tightness check

1. Start the engine and keep it running at idle until vacuum pressure indicates 66.7 kPa (500 mmHg, 19.69 inHg) while the brake pedal is not depressed.

(a)

Pressure gauge

(b)

Vacuum gauge

2. Stop the engine and check the vacuum pressure.

If the value matches the following standard, the vacuum booster assembly function is normal.

Vacuum pressure: standard

The range of vacuum pressure drop within 15 seconds after stopping the engine is 3.3 kPa (25 mmHg, 0.98 inHg) or less.

If a faulty part is detected after inspection, it may results from one of the following causes.

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).

2. Keep the engine running at idle and the pedal depressed until vacuum pressure of the vacuum gauge indicates 66.7 kPa (500 mmHg, 19.69 inHg).

(a)

Pressure gauge

(c)

Pedal force gauge

(d)

Depressed

(b)

Vacuum gauge

3. Stop the engine and check the vacuum gauge.

If the value matches the following standard, the vacuum booster function is normal.

Vacuum pressure: standard

The range of vacuum pressure drop within 15 seconds after stopping the engine is 3.3 kPa (25 mmHg, 0.98 inHg) or less.

If a faulty part is detected after inspection, refer to “AIR TIGHTNESS CHECK”.

Brake Booster > INSPECTION

4. If the vacuum booster assembly is faulty, replace it with a new part.

Lack of boost action check

1. Turn the engine OFF, and set the value of the vacuum gauge to “0”.

2. Check the fluid pressure when the brake pedal is depressed. The pressure must be greater than the specification listed.

Brake pedal force: N (kgf, lbf)

147 (15, 33)

294 (30, 66)

Fluid pressure: kPa (kgf/cm2, psi)

533 (5, 77)

1,551 (16, 225)

Boosting action check

1. Set the vacuum gauge reading to 66.7 kPa (500 mmHg, 19.69 inHg) with the engine running.

2. Check the fluid pressure when the brake pedal is depressed. The pressure must be greater than the specification listed.

Brake pedal force: N (kgf, lbf)

147 (15, 33)

294 (30, 66)

Fluid pressure: kPa (kgf/cm2, psi)

6,177 (63, 896)

11,273 (115, 1,635)

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 completely.• Before handling the airbag sy ...

Installation
1. Check and adjust the operating rod of the vacuum booster assembly.(1) Measure the length between the vacuum booster assembly mounting surface and clevis pin hole.(2) If it is not within the specifi ...

Other materials:

Removal
CAUTION:Vehicle components are extremely hot after driving. Be wary of receiving burns from heated parts.1. Disconnect the ground terminal from battery sensor. NOTE2. Lift up the vehicle.3. Remove the under cover. Front Under Cover > REMOVAL4. Disconnect the front oxygen (A/F) sensor connector (A) ...

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