NEXON BSVI MCE - SERVICE MANUAL

BRAKES 11 3. Brakes Held ON When the brake pedal is held on, the diaphragm will momentarily continue to move forward and thus com- presses the outer edges of the reaction disc. This movement causes the center of the disc to extrude, pressing back the input rod and thus closing the atmospheric port. Thus the output force is balanced against that of the input force. Further movement of the brake pedal either opens the vacuum port or the atmospheric port depending on whether the brake pedal is released or depressed. 4 . Brakes Released Immediately after the brake pedal is released, the vacuum port is opened and the atmospheric pressure in the rear chamber is extracted into the front chamber and from there to the inlet manifold via the non- return valve. The atmospheric port remains closed whilst the input rod assembly returns to its original position as shown in figure. The diaphragm is then again ‘suspended’ in vacuum until the brake pedal is depressed. 8. WORKING OF ANTI-LOCK BRAKING SYSTEM (ABS): 1. ABS is an aid to retain steering control and stability while braking. 2. ABS will not prevent accidents resulting from excessive cornering speeds, following another vehicle too closely or aquaplaning, i.e. where a layer of water prevents adequate contact between tyre and road surface. 3. ABS will not improve braking performance or stopping distance beyond that which is physically possible in relation to road conditions and the vehicles tyres or brakes. 4. The additional control provided by ABS must never be exploited in a dangerous or reckless manner which could jeopardize the safety of driver or other road users. The ABS ECU takes wheel speed information from sensors, located within the hub carrier, and monitors the relative deceleration/acceleration of each wheel at all times. These signals are used to calculate the rotational deceleration (negative acceleration) rates for each wheel during braking operation. In the event of a wheel slip condition (i.e. rotational deceleration being outside of allowable limits) the hydraulic system will control the brake line pressure by operating the appropriate solenoid valves within the hydraulic modulator and thus releasing the brake pressure from that particular wheel. Once the wheel deceleration has recovered to within allowable limits the modulator then allows pressure to be re-applied to the particular brake caliper or wheel cylinder from which the brake pressure was released. When ABS intervention is necessary the warning lamp will not illuminate but the driver will feel the brake pedal pulsating and may experience audible feedback from the modulator indicating that ABS control is taking place. The ABS and EBD warning lamps will illuminate for a system check when the ignition is switched on. Both lamps will then extinguish to indicate the system is healthy. (As the EBD lamp is shared with the Parking brake lamp this will not extinguish until the parking brake is released.) If a fault occurs with the system or any of its constituent components the relevant warning lamp in the instrument cluster will illuminate to inform the driver for the respective fault.