Subaru Legacy

since 1990-1998 release

Repair and operation of the car



Subaru Legacy
+ 1.1. Identification numbers
+ 2. Maintenance
+ 3. Engines
+ 4. Heating, ventilation
+ 5. Fuel system
+ 6. Exhaust system
+ 7. Systems of start, ignition
+ 8. Transmissions
+ 9. Coupling, shaft
- 10. Brake system
   10.1. Introduction
   10.2. Technical characteristics
   10.3. Replacement of brake shoes on disk brakes
   10.4. Support of disk brakes
   10.5. Brake disk
   10.6. Replacement of brake shoes of drum brakes
   10.7. Working brake cylinder
   10.8. Main brake cylinder
   10.9. Brake pipelines and hoses
   10:10. Replacement of the regulator of pressure
   10:11. Pumping of the hydraulic brake system
   10:12. Adjustment of the emergency brake
   10:13. Replacement of a cable of the emergency brake
   10:14. Replacement of brake shoes of the emergency brake on back disk brakes
   10:15. Additional brake system
   10:16. Vacuum amplifier of brakes
   10:17. Stoplight switch
   10:18. Anti-blocking system of brakes (ABS)
+ 11. Suspension bracket
+ 12. Steering
+ 13. Body
+ 14. Electric equipment






10:18. Anti-blocking system of brakes (ABS)

GENERAL INFORMATION

Arrangement of elements of anti-blocking system of brakes on the car

1 – hydraulic control unit and block of control
2 – pressure limiter
3 – diagnostic socket
4 – control lamp of the alarm system
5 – electric socket of data
6 – management and control on the car with the automatic transmission
7 – speed sensor rotor
8 – ABS sensor
9 – support of brakes
10 – G-sensor (only models 4WD)
11 – stoplight switch
12 – main brake cylinder

Arrangement of the hydraulic control unit and block of control on models since 1997


Arrangement of the forward ABS sensor


Arrangement of the back ABS sensor

Efficiency of braking the greatest, when coupling of the tire with the surface of the road maximum. In the course of braking the tire slides on a surface and the district speed of a wheel becomes less than the speed of the car.

Sliding minimum (0%) when the wheel slides freely and maximum (100%) when the wheel is blocked. Maximum efficiency of braking is reached when sliding makes 15%. This size also allows to keep stability and controllability the car.

The role of anti-blocking system consists in restriction of pressure created in hydraulic system of brakes so that the size of sliding kept about the optimum size (15%). Action of this system has to be immediate and separate for each wheel. The system has to answer immediately each change of a surface (coupling coefficient) and load of the car. The anti-blocking system interferes with blocking of wheels at sharp braking. Thanks to it the brake way decreases, especially at low coupling with a paving at a rain and snow. Force of adhesion between wheels and the road in this case is more when when braking a wheel continue rotation. In addition even at full braking the car remains operated. RPM meters on one on each wheel measure the speed of rotation of a wheel. On signals from wheel RPM meters in the electronic operating block the average speed which is approximately corresponding to the speed of the movement of the car is calculated. Comparing the speed of rotation of each separate wheel to the average calculated speed, the electronic block defines a condition of slipping of a separate wheel and by that establishes what wheel is in a preblocking state. When one of four sensors of speed of rotation transmits a signal of blocking of the corresponding wheel, immediately the electronic actuation device gives a closing signal to the corresponding inlet electromagnetic valve which immediately blocks supply of brake fluid via the brake pipeline to a brake of this wheel therefore force of braking remains to a constant. If nevertheless sliding continues, then the final valve and pressure in hydraulic system of this brake opens decreases therefore braking of a wheel decreases. As soon as the wheel starts over again rotating, at once there is an opening of the inlet valve and closing of the final valve. Pressure increases in a contour and the wheel is again braked. Such cycle of braking and free rotation of a wheel occurs very quickly (several times in a second) and proceeds to a car stop, or to a brake pedal otpuskaniye. This process repeats at sharp braking separately for each wheel until the pedal of a brake is released or at reduction of speed of the car to several km/h. The driver defines work of anti-blocking system on a brake pedal pulsation.

The system of emergency shutdown provides shutdown of the ABS system at any malfunction or at low voltage in an electric chain of the car. The electronic actuation device performs also autodiagnostic function, warning the driver fire of a control bulb about registration of malfunction of electric chains or elements of anti-blocking system. At the faulty ABS system of a brake nevertheless are serviceable and function as if this system is not in the car.