11.0 Elements of the ABS system. The pipes in the front of the car are connected to the hydraulic unit
The main elements of the ABS are:
- an electronic control unit combined with a hydraulic unit.
- wheel speed sensors. The front wheel speed sensors are mounted on the steering knuckles, and the rear wheel sensors are mounted on the brake shields. The tightening torque for the front and rear wheel speed sensors is 11 Nm.
- gears on the drive shaft and wheel hub. Sensors receive information about the number of revolutions of the wheel by induction from the gears on the front wheel drive shafts. The rear wheel ABS sensor gears are mounted on the hubs. Due to the fact that the number of teeth on the gears for the cars considered in this manual is strictly defined, the order of ABS parts can only be made with the indication of the model and year of manufacture of the car. To replace the front wheel ABS sensor gear, the drive shaft must be removed, and to replace the rear wheel ABS sensor gear, the hub must be removed.
The main quality of the ABS system is its ability to prevent the wheels from locking during heavy braking. This ensures that the vehicle remains in control. This means that during emergency braking, the driver has a chance to go around the obstacle, due to the fact that the rear wheels are not blocked.
The effect of ABS cannot be overestimated. If the braking force is higher than the physical values for which the ABS is designed, then the car, despite the fact that it is equipped with ABS, may skid.
Wheel speed sensors operate independently of each other and continuously monitor the wheel speed «his» wheels, registering the signal coming from the corresponding gear. If the car is equipped with ABS, but the brake mechanisms of all wheels are disc. At the same time, the possibility of installing drum brakes on the rear wheels is not excluded.
We recommend that you do not carry out any work on the ABS yourself, although some of them are not particularly difficult. The workshop will perform work related to the ABS with higher quality, especially since the ABS is a safety component.
However, the performance of certain types of work on the vehicle may indirectly or directly affect the ABS system. This is especially true for the brake system. Therefore, when performing work on the brake system, a number of requirements must be observed.
1. Clean all connections before disconnecting them.
2. Lay the removed parts on a clean pad and cover them with film or paper. Do not use fluffy rags.
3. Cover exposed parts of the system if repairs are not to be carried out immediately. This is especially important if the car is outdoors.
4. Install only clean parts. Do not install parts that have been removed from the packaging and have been stored for a long time without it.
5. Do not clean parts with compressed air if the brake system is open.
The electronic control unit checks (diagnostics) ABS parts. When a malfunction is detected, the ABS is disabled and the braking system operates as if it were a non-ABS vehicle. In this case, the signal lamp lights up. Contact the workshop.
Front wheel speed sensor - removal and installation
6. Disconnect the wire «masses» (-) from the battery.
7. Loosen the front wheel mounting bolts and place the front of the car on the goats.
8. Remove the front wheel.
9. Disconnect the wheel speed sensor connector. Remember the wire laying and release the wire from the fasteners (in two places).
10. Remove the cover over the wheel speed sensor and unscrew the sensor itself.
The sensor is installed in the reverse order of removal.
11. Check the hole into which the sensor is screwed and make sure it is clean. Lubricate the hole thread with a small amount of grease.
12. Screw in the sensor and tighten it with a torque of 11 Nm.
13. Lay and secure the sensor wire as it was before removal and make sure that it will not fray when the car is moving.
Rear wheel speed sensor - removal and installation
14. Disconnect the wire «masses» (-) from the battery.
15. Place the rear of the vehicle on jack stands.
16. Remember the wire laying and release the wire from the fasteners.
17. Unscrew the sensor.
The sensor is installed in the reverse order of removal.
18. Lubricate the threads of the ABS sensor with protective grease «Loctite».
19. Screw in the sensor and tighten it with a torque of 11 Nm.
20. Lay and secure the sensor wire.