ABS Brake Fluid Replacement Introduction

As you have already studied, three types of ABSs are used in Honda vehicles–one OEM ABS and two Honda-developed ABSs.

In OEM ABS (1996 Civic type), the hydraulic circuit is so constructed that the normal brake fluid replacement and air-bleeding procedures for service brake hydraulic circuit cover the overall brake fluid replacement and air-bleeding services. No additional procedure for ABS is required.

On the other hand, Honda-developed ABSs have ABS control circuits which are independent from the service brake hydraulic circuits. Therefore the brake fluid replacement and air bleeding procedures for ABS control circuit studied in this module are required.

The brake fluid replacement and air-bleeding procedures for two types of  developed ABS – that is, a type in which the accumulator is located separetely from the modulator unit (1990 Accord type) and a type in which the accumulator is incorporated into the modulator unit (1994 Accord type) – are different. Refer to relevant shop manual and study these procedures.

In the brake fluid replacement procedure given in shop manual, draining, refilling, and air-bleeding are performed as three separate operations. The procedures given in this Resource are intended as optional alternatives to the shop manual procedures. They are more efficient since they allow draining and refilling to be performed in a single sequence, thereby eliminating the need for air-bleeding.

You must learn the air-bleeding procedures given the shop manual even if you are going to use the optional procedures given in this Resource. This is because air-bleeding must be performed when modulators are replaced.

2. ABS Brake Fluid Replacement

NOTE:
The brake fluid replacement procedure described in this module applies to the brake fluid in the modulator unit, i.e., the fluid in the high-pressure passages and in the reservoir. Use the conventional brake fluid replacement procedure with the rest of the brake system.

CAUTION:
• Do not loosen the relief plug on the accumulator.
• Place the car on a level surface with the wheels chocked and the transmission in [P] or neutral.

1 Bleeder T-wrench
2 Solenoid head
3 High pressure hose
4 Accumulator/pressure switch
5 Power unit
6 Maintenance bleeder
7 Red cap

1. Open the hood.
2. Remove the red cap from the bleeder screw on the modulator unit.
3. Fit Bleeder T-wrench (special tool) onto the bleeder screw. Slowly turn the wrench by 90 degrees, then give it one complete turn to release the highly pressurized brake fluid and allow it to collect in the wrench.
4. Retighten the bleeder screw and discard the discharged fluid.

NOTE:
Leave a small amount of brake fluid in the reservoir to prevent air from entering the system.

5. Remove the brake fluid in the modulator reservoir using a syringe.
6. Fill the modulator reservoir with brake fluid up to the MAX (upper) line.

Brake Fluid Level

7. Start the engine and let it idle for one minute. The pump will operate to raise the fluid pressure in the high pressure passages. Then, stop the engine.
8. Check the fluid level in the modulator reservoir has dropped. Then, top up the fluid until it reaches the MAX line.
9. Fit Bleeder T-wrench (special tool) onto the bleeder screw. Slowly turn the wrench by 90 degrees, then give it one complete turn to release the highly pressurized brake fluid and allow it to collect in the wrench.

10. Retighten the bleeder screw and discard the discharged fluid.
11. Start the engine and let it idle for one minute. Then, stop the engine.
12. Repeat steps 8 through 11 until fresh brake fluid emerges from the bleeder.
13. Fill the modulator reservoir with brake fluid up to the MAX (upper) line. Then, tighten the bleeder screw to the specified torque and fit the red cap on it.
14. When brake fluid replacement is complete, start the engine and check that the ABS indicator light does not show any abnormality.
15. Connect the ALB checker and perform a function test. If the kickback is weak, perform air-bleeding.

ABS Modulator Unit

1 Accumulator
2 Outlet solenoid valve
3 Inlet solenoid valve
4 Motor
5 Piston/valve
6 Pump
7 Pressure switch

1. Open the hood.
2. Remove the bleeder cap from the maintenance bleeder on the modulator unit.
3. Attach an 8 mm box wrench to the maintenance bleeder.
4. Connect a transparent plastic tube of an appropriate diameter to the bleeder and place the other end of the tube into a suitable container.

Brake Oil Bleeding

CAUTION:
Do not loosen the maintenance bleeder too much since brake fluid may spurt out under great pressure.

5. Holding the tube with one hand, slowly loosen the bleeder by 1/8 to 1/4 of a turn and release brake fluid into the container.
6. Tighten the maintenance bleeder.

NOTE:
Do not remove the tube and wrench yet.

7. Remove the brake fluid in the modulator reservoir using a syringe.
8. Start the engine and let it idle for one minute. The pump will operate to raise the fluid pressure in the high pressure passages. Then, stop the engine.
9. Check that the fluid level in the modulator reservoir has dropped. Then, top up the fluid until it reaches the MAX line.

Brake Fluid Reservoir

10. Holding the tube with one hand, slowly loosen the bleeder by 1/8 to 1/4 of a turn and release brake fluid into the container.
11. Tighten the maintenance bleeder.
12. Start the engine and let it idle for one minute. Then, stop the engine.

13. Repeat steps 9 through 12 until fresh brake fluid emerges from the bleeder.
14. Fill the modulator reservoir with brake fluid up to the MAX (upper) line. Then, tighten the bleeder screw to the specified torque and fit the cap onto it.
15. When fluid replacement is complete, start the engine and check that the ABS indicator light does not show any abnormality.
16. Connect the ALB checker and perform a function test. If the kickback is weak, perform air-bleeding.

ALB Checker Location

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