System Operation

CAUTION: On surfaces which are soft and deep (for example, deep powdery snow, sand or gravel) braking distance may be greater than with non ABS braking. In these conditions wheel lock and the build up of snow or gravel under the wheels may be an aid to shorter stopping distance. However, it is still an advantage to maintain the stability and maneuverability available with ABS control.

OPERATION
1. Switch ON ignition, the system will automatically carry out its self test function. This will be felt as a slight movement in the brake pedal and a short, rapid series of clicks indicating that the solenoid valves have been checked.
2. Observe the warning lights, check that the parking brake/fluid pressure/level warning light extinguishes after initial bulb check or when the parking brake is released, indicating that power assistance is available. Note that the time taken to pressurize the system is approximately 20 seconds.
3. Start the vehicle and drive away, at 7 kph (5 mph) the ABS warning light must be extinguished.
4. In road conditions where surface friction is sufficient to slow or stop the vehicle without wheel lock, the ABS does not operate.
5. In an emergency braking situation, if one or more wheels begin to slow rapidly in relation to vehicle speed, ABS will detect the wheel locking tendency and will regulate the brake pressure to maintain wheel rotation.
6. ABS operation will be felt as a vibration through the pedal, at the same time the solenoid cycling will be heard.

NOTE: Constant pressure on the foot pedal while ABS is operating is more effective than cadence braking. Do not pump the brake pedal as this may reduce ABS efficiency and increase stopping distance.

7. Downward travel of the pedal will also feel hard at the point at which ABS operates. Little further pedal travel is possible at this point, BUT, force on the pedal can be varied to influence braking while ABS retains control.

Brake Application With Partial Failure

CAUTION: If a fault develops in the brake system, it is essential that the driver has the fault investigated immediately.

NOTE: If, during braking, a drastically reduced resistance is detected at the pedal and braking effectiveness is very much reduced, failure of the non-powered (master cylinder) portion of the system is indicated. When this occurs DO NOT PUMP THE BRAKE PEDAL. Push the pedal through the free movement to obtain braking effort. For this reason it is essential that brake pedal travel is not obstructed by the addition of items such as extra footwell mats.

1. When power assistance is not available, ABS braking is not operative. Both warning lights are illuminated. Braking effort is available from the master cylinder only. This results in longer pedal travel and greater pedal effort required to decelerate the vehicle.

CAUTION: Foot pressure on the pedal, using master cylinder only, will not achieve the same degree of braking as that available from power assistance.

2. If the master cylinder fails, i.e. there is insufficient fluid in the master cylinder to create pressure, braking to all four wheels is retained and ABS remains operative. The red warning light will be illuminated if the cause of the master cylinder failure is a fluid leak and the level in the master cylinder is low enough to actuate the fluid level switch.

CAUTION: Longer pedal travel is required, but power assisted braking is available at a reduced efficiency.

3. If brake failure occurs due to a fractured brake pipe between a servo unit and a wheel, there will be no pressure in the reservoir. The fluid warning light will be illuminated when the level in the master cylinder is low enough to actuate the fluid level switch. The master cylinder and power valve will operate as for master cylinder failure. BUT, fluid from the power circuit will push all the moving parts in the servo cylinder associated with the failure to the limit of their travel. No pressurized fluid passes to those brake pistons served by the servo cylinder, but all other pistons in front and rear calipers will be supplied with direct pressure from the power valve. The pistons served by the other servo cylinder retain braking as fluid from the master cylinder is retained in the servo cylinder not associated with the leakage.

CAUTION: Brake pedal travel will be greater and extra pedal effort will be required, accompanied by the vehicle pulling to one side.