Range Rover P38
70
BRAKES
NEW RANGE ROVER
18
DESCRIPTION AND OPERATION
Relays and fuses - Up to 99MY
The ABS electrical system has two relays and three
fuses, located in the engine compartment fusebox.
•
Relay 2 (yellow) - ABS valve relay.
•
Relay 15 (green) - Ignition relay - ABS power.
•
Relay 17 (black) - ABS pump relay. Note that
this relay is unique to the ABS system.
•
Fuse Maxi 3 (40 Amp) - ABS pump relay.
•
Fuse 24 (5 Amp) - ABS ECU - Ignition supply.
•
Fuse 27 (30 Amp) - ABS ECU - Battery supply.
Relays and fuses - From 99MY
The ABS electrical system has two relays and three
fuses, located in the engine compartment fusebox.
•
Relay 15 (green) - Ignition relay - ABS power.
•
Relay 17 (black) - ABS pump relay. Note that
this relay is unique to the ABS system.
•
Fuse Maxi 3 (40 Amp) - ABS pump relay.
•
Fuse 24 (5 Amp) - ABS ECU - Ignition supply.
•
Fuse 38 (30 Amp) - ABS ECU - Battery supply.
Sensors, exciter rings - 4 off
A sensor is mounted at each wheel, sensing a 60
tooth exciter ring. When the vehicle is in motion the
inductive sensors send signals to the ECU.
The front exciter ring is fitted adjacent to the constant
velocity joint in each front hub. The rear exciter ring is
inside the axle adjacent to the wheel bearing
assembly.
NOTE: Road speed information from the
ECU is transmitted to the Body electrical
Control Module (BeCM) to drive the
speedometer and all systems requiring speed
information, except the transfer box ECU.
Brake calipers
Lucas Colette type calipers are used all round. The
front disc brake calipers each house two pistons,
hydraulic pressure is supplied by a combination of
power and hydrostatic circuit. The rear disc brake
calipers each house one piston, hydraulic pressure is
supplied by the power circuit via a Pressure
Conscious Reducing Valve (PCRV).
The operation of both front and rear calipers is in
principle the same. The Colette type caliper consists
of two main components, a carrier and a hydraulic
body assembly. The carrier is bolted to the hub
assembly. The hydraulic body slides on two greased
guide pins housed in the carrier. The guide pins are
sealed by the dust covers to avoid unequal sliding
loads caused by dirt or corrosion.
When the footbrake is applied hydraulic pressure
pushes the piston and, with it, the inboard pad on to
the disc. The hydraulic body reacts and slides on the
guide pins to bring the outboard pad into contact with
the disc. The clamping force on both sides of the disc
is then equal.
When hydraulic pressure is released, the piston seal
retracts the piston a small amount. This allows the
moving parts to relax sufficiently for the brake pads to
remain in close proximity to the disc ready for the next
brake application.