BRAKES (Description): DESCRIPTION AND OPERATION

BRAKES

DESCRIPTION AND OPERATION

70-5

Description

General
The brakes consist of front and rear disc brakes operated by a diagonally split, dual circuit hydraulic system with 
vacuum servo power assistance. The system incorporates the following control functions as standard on all models:

l

Anti-lock Brakes (ABS), to prevent road wheels locking during brake application.

l

Electronic Brake Distribution (EBD), to control distribution of hydraulic pressure between front and rear axles. 
Replaces mechanical pressure limiting valve of previous systems.

l

Electronic Traction Control (ETC), to maintain even torque distribution to the road wheels.

l

Hill Descent Control (HDC), to provide controlled descent ability in off road conditions.

Hydraulic system schematic

1 Master cylinder/brake servo assembly
2 Brake pedal
3 ABS modulator
4 Rear brake

5 Front brake
6 Hydraulic circuit

a Primary

b Secondary

For normal brake operation, brake pedal movement is assisted by the brake servo assembly and transmitted to the 
master cylinder assembly. The master cylinder assembly converts brake pedal movement to hydraulic pressure. 
Primary and secondary brake pipe circuits supply the hydraulic pressure to the brakes via the ABS modulator: the 
primary circuit supplies the front left and rear right brakes; the secondary circuit supplies the front right and rear left 
brakes. Vacuum for the brake servo assembly is obtained from the engine inlet manifold (V8 models) or a vacuum 
pump (diesel models), through a vacuum line and non return valve. To reduce operating noise, sleeving is installed 
on some of the brake pipes in the engine compartment and the pipes are located in sprung pipe clips.

For all control functions, the ABS modulator regulates the hydraulic pressure to the brakes to control the speed of all 
four wheels, either individually or in axle pairs. Operation of the ABS modulator is controlled by the Self Levelling and 
Anti-lock Braking Systems (SLABS) ECU. The SLABS ECU also operates warning indications in the instrument pack 
to provide the driver with status information on each function.