Anti-lock braking system (ABS)

14.9.1. Removing ABS

The operating principle of the anti-lock ABS system is not considered in this manual, but you need to focus on the following points:

- If the vehicle is equipped with ABS, it is usually mounted on the rear axle disc brakes. At the Polo brand vehicles this system is installed in the presence of the rear axle of drum brakes;

- A decisive factor in ensuring security in the ABS operation is the ability to prevent the wheels from locking under heavy braking of the car to improve handling. Even when emergency braking is always preserved a chance to go round an obstacle without the danger of skidding the rear wheel. We should not forget that the ABS can work wonders. Too high speed can bring a car and with ABS;

- Installed in the steering knuckle and the rear hub are four electronic sensor constantly, independently controlled speed gear rims mounted on wheels. In Fig. 311 and 312 is shown where the sensors and ring gears. Signals from the sensors are supplied to an electronic control unit which records and analyzes their abnormality compared with the program inhibition. As a result, the braking force exerted on the corresponding wheel in conjunction with the operation of the hydraulic system of the brake is reduced or increased with a frequency of four to ten times per second, which is much faster than it is possible to achieve a periodic pressing of the brake pedal, and moreover, the braking force adjustable on each wheel separately, and not on all four wheels at the same time when you press the brake pedal on vehicles without ABS;

- Two hydraulic valve accurately allocate the necessary braking force between the front brakes, depending on road conditions. Two control valves control the rear brakes. In this case, the electronic control unit reduces the braking force to the wheel, which is blocked by the first. At the optimal ratio of braking the car remains manageable, preserved its stability and control.

Fig. 313 is a diagram of ABS.

Since the ABS system must provide additional security, not recommended therein any work, although some of them easy to perform. However, if you do some work on the brake system with ABS necessary to comply with the following requirements:

- Before dismantling thoroughly clean all connections and directly adjacent items of equipment;

- The surface where the removed parts must be clean. Details should be covered with foil or a clean paper. Do not use this fuzzy cloth;

- Carefully close the open parts of the system or close them if the repair can not be started immediately. This applies especially to those cases when the car has to be put on the open parking lot;

- Install only absolutely clean parts. In no case do not set back the items that were in storage for a long time;

- If the air compressor is always tempted to use compressed air to clean the parts. In no event it is impossible to do this if the connection open system.

After ignition hydraulic pump for 60 seconds to establish a working pressure in the system. ABS warning light comes on for a time from 2 to 20 depending on the pressure in the system. The electronic control unit starts checking the operation of all system components. If you find any faults brake system works like a conventional system without ABS. If this happens (ABS warning light stays on), you should contact the service station, where with the help of special devices detected a failure in the system, which may be associated with failures in the electric or hydraulic circuit system.