Brakes and Traction Control: Description and Operation

NOTE: Applies to Non ABS Vehicles.

Hydraulic Circuit - Non ABS:

CONSTRUCTION
The servo assisted hydraulic braking system is the dual line type, incorporating primary and secondary hydraulic circuits.

NOTE: References made to primary or secondary do not imply main service brakes or emergency brakes but denote hydraulic line identification.

The brake pedal is connected to a vacuum assisted mechanical servo which in turn operates a tandem master cylinder. The front disc brake calipers each house four pistons. These pistons are fed by the secondary hydraulic circuit. The rear disc brake calipers each house two pistons. These are fed by the primary hydraulic circuit via a pressure reducing valve.

A brake fluid level switch is incorporated into the reservoir cap assembly, the switch will immediately illuminate a warning light in the instrument panel indicating low fluid or sudden fluid loss.

OPERATION
The brake fluid reservoir is divided; the section closest to the servo feeds the primary circuit and the section furthest from the servo feeds the secondary circuit. Under normal operating conditions both the primary and secondary circuits operate simultaneously on brake pedal application. In the event of a failure in the primary circuit the secondary circuit will still function. If the secondary circuit fails the primary circuit will still function. The brake pedal travel will be longer in the event of a half system failure.

If the servo should fail, both hydraulic circuits will still function but would require greater pedal effort due to the lack of vacuum assistance. The hand operated parking brake acts on a brake drum at the rear of the transfer gearbox and is completely independent of the hydraulic circuits.