Brake system technical data
The brake system consists of a master brake cylinder, a vacuum brake booster and disc brakes for the rear and front wheels. The brake hydraulic system is divided into two circuits, functioning diagonally. One hydraulic circuit acts on the front right and rear left wheels, and the other - on the front left and rear right. This makes it possible to stop the vehicle with sufficient efficiency in the event of, for example, a leak in one of the circuits of the brake system. The pressure for both circuits is created by the dual master brake cylinder when the brake pedal is actuated.
The expansion tank with brake fluid is located in the engine compartment above the master brake cylinder and is closed with a lid. The entire brake system is supplied with brake fluid from it.
The vacuum brake booster on vehicles with a gasoline engine uses the vacuum in the intake manifold and increases the applied force when the brake pedal is depressed. Due to the fact that a diesel engine has almost no vacuum in the intake manifold, vehicles with a diesel engine are equipped with a special brake booster vacuum pump. The vacuum pump on vehicles with a 4-cylinder diesel engine is mounted on the cylinder block on the left side and is driven by an intermediate shaft. On vehicles with a 6-cylinder diesel engine, the vacuum pump is installed on the front side of the left cylinder head.
Disc brakes are equipped with a so-called floating caliper, formed by a caliper and wheel cylinder, which are bolted together. One piston is installed in the cavity of the wheel cylinder, which provides sufficient pressure of both brake pads to the brake disc.
The parking brake acts through a cable drive on the brake mechanisms of the rear wheels.
Attention! Work on the brake system requires meticulous cleanliness and precision. If the necessary experience is not available, it is better to entrust such work to a specialized workshop.
AUDI ALLROAD cars are also equipped with systems that increase stability, as well as active safety. Such systems are ABS/EBV/EDS/ASR/ESP. Available with Bosch ABS/ESP version 5.7 or 5.3 (see illustrations 1.0 and 1.0a).
The anti-lock braking system (ABS) prevents the wheels from locking during hard braking. Thanks to this, the car remains steerable even when braking to a complete stop.
brake force distributor (EBV) redistributes braking force between the rear wheels using ABS hydraulics. The electronic brake force distributor has more «sensitivity», than mechanical, and, accordingly, the range of its capabilities is much wider.
When driving in a straight line, the brake mechanisms of the rear wheels in the event of braking are activated with full efficiency. In order to ensure the stability of the vehicle during cornering braking, it is necessary to reduce the braking effect experienced by the rear wheels. Based on the information transmitted by the ABS sensors about the speed of rotation of the wheels, the electronic distributor recognizes whether the car is moving in a straight line or making a turn. When cornering, the braking force on the rear wheels is reduced, which provides them with maximum lateral force.
By electronic differential lock (EDS) the slipping wheel is braked, and the traction force is transferred to the wheel that does not slip, but has a stronger grip on the soil or road surface.
EDS turns on immediately at the moment of starting the movement and automatically turns off when the car develops a speed of about 40 kilometers per hour. EDS does not affect the dynamic properties of the car and does not reduce the comfort of driving during acceleration.
Vehicle stability stabilization system (ESP) reduces the risk of skidding by automatically adjusting the braking force. If, for example, the rear of the car begins to skid, then the front wheel located on the outside of the turn is braked through the ABS hydraulics, which stabilizes the stability of the car.
Anti-slip system (ADS) reduces the torque transmitted to the drive wheels if they slip.
The interlock in the ABS / EBV / EDS / ASR / ESP control unit ensures automatic shutdown of the system in the event of a malfunction, for example, when the power wire is broken or when the battery voltage drops below 10 V. The deactivation of the corresponding system is signaled by the corresponding control lamp on the instrument panel. The normal braking system remains in effect when the ABS/EBV/EDS/ASR/ESP is deactivated. In this case, the vehicle behaves as if it were not equipped with ABS.
Attention! If the ABS and brake system warning lights come on while driving, remember that in the event of sudden braking, the rear wheels may be blocked due to lack of brake force control.
If, while driving, one or more warning lights on the instrument panel come on, it is recommended to do the following:
1. Stop, turn off the engine, and then start it again.
2. Check battery voltage. If the battery voltage is less than 10.5 V, then charge the battery.
Attention! If the warning lights come on at the beginning of the movement, and go out after a while, then this indicates that the battery voltage was too low, but then increased during the movement as a result of recharging from the generator.
3. Check if the wire terminals are securely fastened to the battery terminals.
4. Place the vehicle on jack stands and remove the wheels. Check wheel speed sensor wires for external damage (grinding). Further checking of ABS/EBV/EDS/ASR/ESP must be carried out in a workshop.
Attention! When working with electric welding, the plug of the ABS/EBV/EDS/ASR/ESP electronic unit must be disconnected. Disconnect the plug only when the ignition is off. When performing paint work, the control unit can be subjected to short-term exposure to high temperatures not exceeding +95°C and long-term (maximum within 2 hours) temperature not higher than +85°С.
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