EBD (ELECTRONIC BRAKE-FORCE DISTRIBUTION) OPERATION
The EBD system (Electronic Brake force Distribution) as a sub-system of the ABS system is to control the effective adhesion utilization by the rear wheels.
It further utilizes the efficiency of highly developed ABS equipment by controlling the slip of the rear wheels in the partial braking range.
The brake force is moved even closer to the optimum and controlled electronically, thus dispensing with the need for the proportioning valve.
The proportioning valve, because of a mechanical device, has limitations to achieve an ideal brake force distribution to the rear wheels as well as to carry out the flexible brake force distribution proportioning to the vehicle load or weight increasing. And in the event of malfunctioning, driver cannot notice whether it fails or not.
EBD controlled by the ABS Control Module, calculates the slip ratio of each wheel at all times and controls the brake pressure of the rear wheels not to exceed that of the front wheels.
If the EBD fails, the EBD warning lamp (Parking brake lamp) lights up.
Operation and Leakage Check
Check all of the following items
| Component | Procedure |
|---|---|
| Brake Booster (A) | Check brake operation by applying the brakes during a test drive. If the brakes do not work properly, check the brake booster. Replace the brake booster as an assembly if it does not work properly or if there are signs of leakage. |
| Piston cup and pressure cup inspection (B) | Check brake operation by applying the brakes. Look for damage or signs of fluid leakage. Replace the master cylinder as an assembly if the pedal does not work properly or if there is damage or signs of fluid leakage. |
| Check for a difference in brake pedal stroke between quick and slow brake applications. Replace the master cylinder if there is a difference in pedal stroke | |
| Brake hoses (C) | Look for damage or signs of fluid leakage. Replace the brake hose with a new one if it is damaged or leaking. |
| Caliper piston seal and piston boots (D) | Check brake operation by applying the brakes. Look for damage or signs of fluid leakage. If the pedal does not work properly, the brakes drag, or there is damage or signs of fluid leakage, disassemble and inspect the brake caliper. Replace the boots and seals with new ones whenever the brake caliper is disassembled. |
| Wheel cylinder piston cup and dust cover (E) | Check brake operation by applying the brakes. Look for damage or signs of fluid leakage. If the pedal does not work properly, the brakes drag, or there is damage or signs of fluid leakage, replace the wheel cylinder. |
BRAKE SYSTEM REPAIR PROCEDURE CHART
Scheme 1
DESCRIPTION
Do not disassemble the proportioning valve. The proportioning valve makes the ideal distribution of fluid pressure to the front and rear brakes to prevent the brakes from skidding in the event of rear wheel lock up and to obtain higher brake efficiency within the range of service brake application.
Scheme 2
Scheme 3
- Remove the front brake tube (B) and rear brake tube (C) from the master cylinder (A).
- Connect two pressure gauges (D); one to the output valve of the front (B) and rear (C) brake. NOTE: Be sure to bleed the system after connecting the pressure gauges.
- With the brake applied, measure the front pressure and the rear pressure. If the measured pressures are within the specified range as illustrated, the proportioning valve is good.
- Reconnect the brake lines in their original positions and bleed the brake system. NOTE: This table shows characteristics of the proportioning valve as the pressure increases. PROPORTIONING VALVE SPECIFICATION CHART Front (Output of master cylinder) Rear (Output of proportioning valve) A : 30 kg/cm 2 (2.94 MPa, 427 psi) A' : 30 kg/cm 2 (2.94 MPa, 427 psi) B : 65 kg/cm 2 (6.37 MPa, 925 psi) B' : 39.5 ± 3.0 kg/cm 2 (3.87 ± 0.3 MPa, 562 ± 43 psi)
Scheme 4
Scheme 5
Scheme 6
- Disconnect the brake hose (C) from the brake line (A) using a flare-nut wrench (B).
- Remove the brake hose clip (A), and then remove the brake hose (B).
- Remove the connector bolt from the caliper, and disconnect the brake hose from the caliper.
Scheme 7
Scheme 8
Scheme 9
- Disconnect the brake hose (B) from the brake line (A) using a flare-nut.
- Remove the brake hose (B) from the brake line (C) using a flare-nut.
- Remove the brake hose clip (D), and the remove the brake hose.
- Disconnect the brake tube (C) from the drum brake using a flare-nut.
Scheme 10
Scheme 11
- Install a brake hose (A) on the caliper with tightening brake hose bolt (C) and washer (B).
- Install the brake hose clip (C) to the brake hose bracket (B), then install the brake hose (A).
- Connect the brake hose to the brake line.
- After installing the brake hose, bleed the brake system. CAUTION: Check the brake hoses for interference and twisting. Check the brake hose and line joint for leaks, and tighten if necessary.
Scheme 12
Scheme 13
- Install a brake tube (C) on the drum brake using a flare-nut.
- Install the brake hose clip (D) to brake hose bracket, the install the brake hose (B).
- Connect the brake hose (B) to the brake line (A) using a flare-nut.
- Connect the brake hose to the brake line (A).
- After installing the brake hose, bleed the brake system. CAUTION: Check the brake hoses for interference and twisting. Check the brake hose and line joint for leaks, and tighten if necessary.