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Brake System (2008-2012): Overview

Fig 1: Identifying Overview Of Brake System
GLL156788Courtesy of VOLVO CARS CORPORATION
Number  Designation  Number  Designation 
1 Wheel sensor 6 Brake pipe
2 Power brake booster 7 Brake control module (BCM)
3 Brake hose 8 Protective panel
4 Brake caliper 9 Vacuum pump
5 Brake disc    

The vehicle has two brake systems that are independent of each other:

The power brake booster is actuated directly by the brake pedal. It ensures that less pedal force is required when braking with the aid of vacuum from the vacuum pump and/or the intake manifold for the engine.

Brake system 

The brake control system comprises:

As well as on vehicles without a vacuum pump:

Fading Brake Support (FBS) 

Fading Brake Support aids the driver to increase the brake pressure in the system in the event of hard braking. This is to compensate for the high pedal force that is normally needed when the brake discs are hot.

The system detects the pressure in the main cylinder set against the vehicle's retardation. If retardation is not sufficient, the pressure increases from the hydraulic unit to both circuits until maximum retardation is achieved.

The pressure in both the circuits increases until ABS control is achieved.

Pressurization of Ready Alert Brakes (RAB). 

The brake system is pressurized to prepare the brake system for any panic braking.

The system detects the speed at which the driver released the accelerator pedal. If this occurred quickly, the hydraulic unit starts and prefills the brake calipers. This is to eliminate any clearance between the brake pads and discs, which shortens the reaction time of the brake system.

In order for the system to activate, the driver must not have braked and the accelerator pedal must have been released quickly.

Brake Pressure Support (BPS) 

Brake Pressure Support is found on vehicles, without a vacuum pump, between the engine's intake pipe and power brake booster (V8) and compensates poor servo assistance in the event of poor vacuum.

Brake Pressure Support uses the double pressure sensor on the power brake booster and when the pressure difference between the front and rear chambers is too small during braking, the system cuts in.