Mercedes S-class W202

1993-2000 of release

Repair and car operation

Mercedes W202
+ 1.2. The general data
+ 2. Maintenance service
+ 3. Engines
+ 4. Greasing system
+ 5. Cooling system
+ 6. Heating, ventilation
+ 7. Ignition system
+ 8. Fuel system
+ 9. Transmission
+ 10. A running gear
+ 11. A steering
- 12. Brake system
   12.2. Antiblocking system – ABS
   12.3. The additional equipment – system ASR
   12.4. Specifications of brake system
   12.5. Overlays of lobbies brake колодок
   + 12.6. Overlays of back disk brakes
   12.7. A support
   12.8. A forward brake disk
   12.9. A back brake disk
   12.10. A brake liquid
   12.11. Removal of air from brake system
   12.12. Brake pipelines / hoses
   12.13. Replacement of brake highways
   12.14. Brake колодки a lay brake
   12.15. Adjustment of a lay brake
   12.16. The stoplight switch
   12.17. Diagnostics of malfunctions of brakes
   + 12.18. Wheels and tyres
+ 13. A body
+ 14. An electric equipment
+ 14.2. Electroschemes

12.2. Antiblocking system – ABS

Serial system ABS prevents blocking of brakes at sharp braking. Thanks to it the car remains operated. System ABS works at speed more than 5 km/h and at the included ignition. It completely regulates braking process if speed of the car at least has unitary exceeded 8 km/h.

The system measures speed of rotation of wheels by means of two gauges on forward wheels and one gauge – on back. On signals of separate gauges the electronic device calculates rough average speed of the car. By means of comparison of speed of the car the operating device defines degree of proslipping of a separate wheel and establishes, brakes are how much close to blocking.

As soon as the wheel has shown propensity to blocking, system ABS blocks pressure upon a brake, keeping its given condition. It means that pressure in the brake mechanism does not raise even in that case when pressing a brake pedal increases. If and further there is a propensity to blocking pressure in the given brake decreases system ABS at the expense of opening of the final valve. This process goes until the wheel again will not start to be accelerated.

If the wheel again starts to be accelerated, ABS raises pressure in its brake system, but it does not reach value of pressure in the general brake system. This process repeats at sharp braking for each wheel so long, the brake pedal, accordingly, to a full stop of the car (speed of 3 km/h) will not be released yet.

The safety system in an electronic monitor watches that ABS it was disconnected at a faulty food or too a low voltage (pressure on the accumulator less than 11); in this case on the panel of devices during a trip control radiator ABS lights up. The brake system thus functions as usually. The car at braking behaves as if system ABS is absent.

The hydraulic device consists of the pump of return giving, and also from three electromagnetic valves – on one for forward wheels, and one – for back brakes.

Pressure increase: the inlet valve in the device of the electromagnetic valve is opened, pressure of a liquid in the brake mechanism can raise to value which is provided with the main brake cylinder.

Pressure is constant: inlet and final valves in the device of the electromagnetic valve are closed. Pressure of a liquid in the brake mechanism does not change, even if pressure between the main brake cylinder and the electromagnetic valve raises.

Pressure decline: the inlet valve in the electromagnetic valve is opened. The brake liquid follows through the store, from which it закачивает back in system of the main brake cylinder the pump of return giving.

It is required, that the liquid from the main brake cylinder was not lost. Work of this pump is felt on appreciable pulsations of a brake pedal. Pump noise are weakened with the help демпфера a brake contour.

If during a trip indicator ABS lights up, it specifies that system ABS is disconnected.

1. Stop the car, muffle the engine and again get it.
2. Check up pressure of the accumulator. If pressure less than 11 In, charge it.
The prevention

If indicator ABS is shone from the very beginning of a trip, and then dies away, it is necessary to search for the reason in additional charge of accumulator originally available too a low voltage.

3. Raise the car, remove forward wheels, survey electric wires on external damages (протертости).

The further checks ABS should be spent in a workshop. The operating device tests system ABS before each trip and remembers the appeared malfunctions which codes remain in its memory even at accumulator switching-off. In firm workshops these errors will be decoded by means of the special device, and then purposefully eliminated.