Anti-lock device (VW Golf 3)

Usually, if a car is equipped with an anti-lock device, disc brakes are mounted on its rear axle. However, in the Golf version, this device (depending on the model) can also function when drum brakes are placed on the rear axle.

The decisive safety factor provided by the anti-lock braking system is its ability to prevent the wheels from locking when the vehicle brakes sharply; thanks to this, the possibility of further control of the car in this situation is guaranteed. Even with emergency braking, there is still a chance that the obstacle can be driven around, maintaining control over the rear wheels. But we must never forget that the anti-lock device cannot perform miracles. If the physical capabilities of the device are exceeded, i.e. the speed is too high, then the car with the anti-lock device will also begin to slip.







The rotation speed of each wheel is controlled independently by four electronic sensors that record the wheel speed readings. The sensors are mounted on the pivot pin or rear support of the wheel hub and actually "monitor" the speed of the toothed rims located at the end of the axle. The figure shows where the sensors and toothed rims are located in the versions with disc and drum brakes, respectively.



Shown is what a disc brake looks like when fitted to the front of a car, if an anti-lock device is fitted. The computer records these signals indicating the number of revolutions and evaluates any deviations in relation to the pre-programmed values. Thanks to this process, in combination with the hydraulic device, the brake pressure on the corresponding wheel can be increased or decreased 4-10 times per second, which is much faster than can be achieved by "intermittent" pressing of the brake pedal. In addition, the brake adjustment can be made on each wheel separately, rather than all four wheels simultaneously, which is the case when pressing the brake pedal in cars that do not have an anti-lock device.


Two hydraulic valves distribute the required pressure to the front brakes precisely depending on the road conditions. Another control valve controls the rear brakes. In this case, the electronic control system first reacts to the wheel that is locked first. With optimal braking, the vehicle remains steerable.

Since the anti-lock device is supposed to provide you with additional safety, we do not recommend carrying out any other work on it, although some operations will not cause you any trouble. However, a workshop will be able to better understand the situation. Nevertheless, the car is always subject to some work that will undoubtedly affect the anti-lock device, since even during normal work carried out on the braking system, for example, bleeding air from the system is carried out in different ways. For this reason, when carrying out any work on the braking system, the following requirements must be taken into account.

Clean all connecting elements and their surrounding areas thoroughly before disconnecting them.

Place dismantled parts on a clean surface and cover with plastic film or clean paper. Do not use any fibrous rags for this purpose.

Carefully cover or close open parts of the device if the repair will be done at a later date. This is especially important when the car is parked outdoors.

Mount only completely clean parts; never use parts that have been lying around for a long time.

If you have air compressors that can be connected instead of the cigarette lighter, you can always successfully use compressed air to clean the parts. Never carry out this operation with the connecting elements of the device open.

After the ignition system is switched on, the hydraulic pump establishes the required operating pressure in the device within 60 seconds. The special lighting of the anti-lock device flashes for 2-20 seconds, depending on the pressure in the device. Now the electronic control device checks the individual components of the anti-lock device. If any deviations are noticed, the braking system will work as a traditional system without an anti-lock device. In this case, i.e. if the signal light continues to burn, you should contact the workshop. Specialists, using the failure diagnostic system, will be able to find a malfunction in the device caused by failures in the electronics or hydraulics.