POWER BRAKE UNIT INSPECTION

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  Note
  • The following inspection methods are simple inspection methods to judge the function of the power brake unit.
  • If there is any malfunction in the power brake unit, replace the power brake unit as a single unit.

Without Using SST

Operation inspection

1. With the engine stopped, pump the pedal a few times.

2. With the pedal depressed, start the engine.

3. If the pedal moves down slightly immediately after starting the engine, the unit is normal.

Vacuum function inspection

1. Start the engine.

2. Stop the engine after driving the vehicle for 1—2 min.

3. Depress the pedal with normal force.

4. If the first pedal stroke is long and becomes shorter with subsequent strokes, the unit is normal.

  • If a problem is found, inspect for damage to or improper installation of the check valve and vacuum hose. After repairing, inspect again.

Vacuum loss function inspection

1. Start the engine.

2. Depress the pedal with normal force.

3. With the pedal depressed, stop the engine.

4. Hold the pedal depressed for approx. 30 s.

5. If the pedal height does not change during this time, the unit is normal.

Using SST

Pre-inspection preparation

1. Disconnect the brake pipe flare nut area using the commercially available flare nut wrench as shown in the figure.

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2. Remove the clamp and disconnect the brake hose.

3. Install the SSTs to the brake pipe as shown in the figure.

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4. Bleed the brake line and the SSTs of air. Bleed the air form the SSTs using bleeder screw A.

5. Install the pedal force gauge to the brake pedal.

6. Connect the vacuum gauge to the vacuum line.

Vacuum loss inspection

1. Start the engine.

2. Depress the brake pedal with a force of 200 N {20.4 kgf, 44.9 lbf}.

3. Stop the engine when the vacuum gauge reading reaches 68 kPa {510 mmHg, 20.1 inHg} with the pedal depressed.

4. With the engine off, observe the vacuum gauge for 15 s.

5. If the gauge has dropped 3.3 kPa {25 mmHg, 1.0 inHg} or less, the unit is normal.

Lack of hydraulic pressure inspection

1. If the pedal force and fluid pressure correlation is within the specification with the engine stopped and a vacuum amount of 0 kPa {0 mmHg, 0 inHg}, the system is normal.

Master cylinder fluid pressure

Vacuum amount at o kPa {0 mmHg, 0 inHg}
Pedal force | Fluid pressure
--- | ---
200 N {20.4 kgf, 44.9 lbt} | 520 kPa {5.31 kgf/cm2, 75.5 psi} or more

Hydraulic pressure inspection

1. Start the engine. Depress the brake pedal when the vacuum reaches 66.7 kPa {500 mmHg, 19.7 inHg}.

2. At this time, apply the indicated pedal force and if the fluid pressure is within the specification, the unit is normal.

Master cylinder fluid pressure

Vacuum amount at 66.7 kPa {500 mmHg, 19.7 inHg}
Pedal force | Fluid pressure
--- | ---
200 N {20.4 kgf, 44.9 lbt} | 9,000 kPa {91.78 kgf/cm2, 1,306 psi} or more

After-inspection procedure

1. After the inspection, remove the SSTs, install the brake hose, clamp, and brake pipe to the original positions, and then bleed the air from the brake line.

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