Range Rover Classic
BRAKES
3
DESCRIPTION AND OPERATION
Petrol engine vacuum system
The vacuum necessary to operate the brake servo on
petrol engine vehicles is provided by the engine inlet
manifold. During normal operation of the brakes only a
small volume of air is drawn from the servo and into
the inlet manifold or plenum chamber. However any
excessive air leaks due to damage in the brake servo
system or manifold hose connection, will effect the
mixture strength and ECM fuelling calculations on
engines equipped with an MFI system.
See FUEL
SYSTEM, Description and operation, Hot Wire
Multiport Fuel Injection
Diesel engine vacuum system
As the diesel engine inlet system does not produce
depression sufficient to operate the brake servo, it is
necessary to install an engine driven vacuum pump.
During normal operation of the brakes only a small
volume of air is drawn from the servo by the vacuum
pump. However as the pump exhausts air into the
engine crankcase atmosphere, an air leak due to
damage in the brake servo system or pump hose
connection, may cause excessive crankcase
pressure.
BRAKE SYSTEM
Description
The servo assisted hydraulic braking system is the
dual line type, incorporating primary and secondary
hydraulic circuits, see illustration RR2225M.
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, the upper pistons are fed by the
primary hydraulic circuit, the lower pistons by the
secondary hydraulic circuit. The rear disc brake
calipers each house two pistons, these are fed by the
secondary 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 binnacle
indicating low fluid or sudden fluid loss.
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
and operate front and rear calipers. Alternatively, if the
secondary circuit fails the primary circuit will still
function and operate the lower pistons in the front
calipers, allowances should be made and vehicle
speed adjusted accordingly to allow for the lack of full
braking efficiency.