POWER BRAKE UNIT INSPECTION

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Caution

•  Once the brake switch clearance has automatically been adjusted, it cannot be adjusted again. Therefore, replace the switch with a new one when replacing the power brake unit or performing any procedure that changes the pedal stroke.

•  Brake fluid will damage painted surfaces. Be careful not to spill any on painted surfaces. In addition, if there is any brake fluid on the wiring harness, the wire insulation may corrode causing a malfunction such as a short circuit. If brake fluid gets on a painted surface or wiring harness, wash and flush it off completely with water immediately.

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.

•  Tighten the brake pipe flare nut using any commercially available flare nut wrench.

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

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.

Pre-inspection preparation

1.  Disconnect the brake pipe from the brake hose.

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2.  Remove the clip.

3.  Remove the brake hose from the bracket.

4.  Detach the brake pipe from the pipe holder.

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

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

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

8.  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, 45.0 lbf}.

3.  Stop the engine when the vacuum gauge reading reaches 68 kPa {510 mmHg, 20 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, 0.97 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.

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.

After-inspection procedure

1.  After the inspection, remove the SSTs, install the brake hose, clip, and brake pipe to the original positions, and then bleed the air from the brake line. (See BRAKE HOSE (FRONT) REMOVAL/INSTALLATION.) (See BRAKE FLUID AIR BLEEDING.)