Diesel Data: Automotive Repair
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Brake Pressure Modulator Valve







CAUTION: Do not spill brake fluid on the car; it may damage the paint; if brake fluid does contact the paint, wash it off immediately with water.






Relieving Accumulator/Line Pressure

WARNING: Use the Bleeder T-wrench before disassembling the parts shaded in the illustration.

1. Open the hood.
2. Remove the red cap from the bleeder on the modulator body.
3. Install the special tool on the maintenance bleeder and turn it out slowly 90°to collect high-pressure fluid into the reservoir. Turn the special tool out one complete turn to drain the brake fluid thoroughly.
4. Retighten the maintenance bleeder and discard the fluid.
5. Reinstall the red cap.
Reservoir Brake Fluid Draining
1. Draining brake fluid from modulator tank:
The brake fluid may be sucked out through the top of the modulator tank with a syringe. It may also be drained through the pump joint after disconnecting the pump hose.
2. Draining brake fluid from master cylinder:
Loosen the bleed screw and pump the brake pedal to drain the brake fluid from the master cylinder.

WARNING: High-pressure fluid will squirt out if the shaded hose and pipe are removed.

- To drain high-pressure brake fluid, follow the procedure for releaving accumulator line pressure.






Modulator/Pump
Removal/Installation

CAUTION:

- Be careful not to bend or damage the brake pipes when removing the modulator unit.
- Do not spill brake fluid on the car; it may damage the paint; if brake fluid does contact the paint, wash it off immediately with water.
- To prevent spills, cover the hose joints with rags or shop towels.
- Before reassembling, check that all parts are free of dust and other foreign particles.
- Do not mix different brands of brake fluid as they may not be compatible.
- Do not reuse the drained fluid. Use only clean DOT 3 or 4 brake fluid.
- When connecting the brake pipes, make sure that there is no interference between the brake pipes and other parts.
1. Remove the battery and battery tray.
2. Disconnect the solenoid, motor and pressure switch connectors.
3. Disconnect the brake pipes from the modulator unit.
4. Remove the mounting bolts and nut, then remove the modulator/ABS pump assembly from the frame.
5. Install the modulator/ABS pump assembly in the reverse order of removal.
6. After installation, bleed the air from the system.






Modulator/Pump
Index/Torque
Before removing the modulator-to-pump high-pressure line, be sure to relieve the pressure fluid from the maintenance bleeder. Refer to Relieving Accumulator/Line Pressure above.


CAUTION:
- Do not spill brake fluid on the car; it may damage the paint; if brake fluid does contact the paint, wash it off immediately with water.
- To prevent spills, cover the hose joints with rags or shop towels.
- Before reassembling, check that all parts are free of dust and other foreign particles.
- Do net mix different brands of brake fluid as they may not be compatible.
- Do not reuse the drained fluid. Use only clean DOT 3 or 4 brake fluid.
- Do not try to disassemble the modulator unit and pump assembly. Replace the modulator unit as an assembly if it is defective.






Solenoids
Leak Test

NOTE: If a solenoid leaks excessively, the brake fluid level in the modulator reservoir tank will rise when operating the ABS motor. The modulator reservoir may also overflow.

1. Connect an ohmmeter between the YEL and YEL terminals of the pressure switch connector.
2. Attach the positive (+) lead of a fully charged 12 V battery to the RED/WHT terminal of the motor connector and negative (-) lead to the GRN terminal, and install a switch between negative lead and GRN terminal as shown.
3. Turn the switch on to allow sufficient pressure to build up within the accumulator and check for continuity. If the ohmmeter shows continuity (pressure switch turned on), run the motor for 10 seconds more, then turn the switch off.
- Check if the solenoid hisses or squeaks. Replace the modulator unit if the solenoid hisses or squeaks.
- Check the pressure switch for continuity within 30 minutes. It is normal if there is continuity. If there is no continuity, a solenoid is faulty or there is a high-pressure line leak.
Accumulator
Replacement
- Before removing the modulator-to-accumulator high pressure line, be sure to relieve the pressure fluid from the maintenance bleeder. Refer to Relieving Accumulator/Line Pressure above.
1. Loosen the flare nuts and remove the accumulator pipe






2. Remove the three mounting bolts and the accumulator from the modulator unit.
3. Install a new accumulator in the reverse order of removal.
4. Bleed the air from the high-pressure line. Refer to Air Bleeding with ALB Checker below.
Disposal
The accumulator contains high pressure nitrogen gas. Do not puncture, expose to the flame, or attempt to disassemble the accumulator or it may explode and severe personal injury may result.
1. Secure the accumulator in a vise so that the relief plug points straight up.
2. Slowly turn the plug three and a half turns and then wait three minutes for all pressure to escape.






3. Remove the plug completely and dispose of the accumulator.
Bleeding
Air Bleeding with ALB Checker

CAUTION:
- Do not spill brake fluid on the car; it may damage the paint; if brake fluid does contact the paint, wash it off immediately with water.
- Make sure no dirt or other foreign matter is allowed to contaminate the brake fluid.
- Do not mix different brands of brake fluid as they may not be compatible.
- Do not reuse the drained fluid. Use only clean DOT 3 or 4 brake fluid.
1. Place the vehicle on level ground with the wheels blocked. Put the transmission in neutral for manual transmission models, and in (P) position for automatic transmission models. Release the parking brake.






2. Disconnect the ABS inspection connector (6P) from the cross-member under the passenger's seat and connect the ABS inspection connector (6P) to the ALB checker.






3. Fill the modulator reservoir to the MAX level line and install the reservoir cap.
4. Start the engine and allow it to idle for a few minutes, then stop it. Check the fluid level in the modulator reservoir and refill to the MAX level line if necessary.






5. Bleed high-pressure fluid from the maintenance bleeder with the special tool.
6. Refill the modulator reservoir to the MAX level line and install the reservoir cap.
7. Turn the Mode Selector switch of the checker to 2.
8. While depressing the brake pedal firmly, push the Start Test switch to operate the modulator. There should be kickback on the brake pedal. If not, repeat steps 5 to 8.

NOTE: Continue to depress the brake pedal firmly when operating the checker.

9. Turn the Mode Selector to 3, 4, and 5. Perform step 8 for each of the test mode positions.
10. Refill the modulator reservoir to the MAX level line and install the reservoir cap.
WARNING: Disconnect the ALB check before driving the car. A collision can result from a reduction, or complete loss of braking ability causing severe personal injury or death.
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