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, depress the brake pedal several times.

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

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

Vacuum function inspection

1. Start the engine.

2. After driving the vehicle for 1—2 min, stop the engine.

3. Depress the brake 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 brake pedal with normal force.

3. With the brake pedal depressed, stop the engine.

4. Maintain the brake pedal depressed for approx. 30 s.

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

Using SST

  Note
  • When performing the inspection using the SST, inspect the brake pipe on the left or right front wheel.
  • The following procedure and figures show the inspection for the brake pipe on the left front wheel.

Preparation before inspection

1. Loosen the brake pipe flare nut using the commercially available flare nut wrench.

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2. Disconnect the brake pipe.

3. Remove the bolt and disconnect the brake hose.

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

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5. Perform air bleeding of the SST and brake line from bleeder screw A.

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

7. Connect the vacuum piping to the vacuum gauge.

Checking for vacuum loss (loaded condition)

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 brake pedal depressed.

4. Measure the amount of vacuum decrease for 15 s immediately after stopping the engine.

5. If the amount of vacuum decrease is 3.3 kPa {25 mmHg, 1.0 inHg} or less, the power brake unit is normal.

Lack of hydraulic pressure inspection

1. With the engine stopped and the vacuum amount at 0 kPa {0 mmHg, 0 inHg} if the pedal force and fluid pressure correlation is within the specification, the system is normal.

Power brake unit fluid pressure

Vacuum amount at o kPa {0 mmHg, 0 inHg}
Pedal force (N {kgf, lbf}) | Fluid pressure (kPa {kgf/cm2, psi})
--- | ---
200 {20.4, 44.9} | 620 {6.33, 90.0} or more

Hydraulic pressure inspection

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

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

Power brake unit fluid pressure

Vacuum amount at o 66.7 kPa {500 mmHg, 19.7 inHg}
Pedal force (N {kgf, lbf}) | Fluid pressure (kPa {kgf/cm2, psi})
--- | ---
200 {20.4, 44.9} | 6,340 {64.65, 919.6} or more

Procedure after inspection

1. Remove the SSTs after the inspection and install the brake hose, bolt and brake pipe to their original positions.

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2. Perform air bleeding of the brake line. (See AIR BLEEDING.)