Ford Orion. Manual - part 50
2 Detach the brake pipes from the valve (see
illustration), and drain the fluid into a suitable
container for disposal. Due to its location,
care will be needed not to spill the fluid onto
the hands - wear suitable protective gloves.
3 Detach the spring clip from the link rod at
the axle end. Withdraw the washer and the
valve link rod from the bracket on the axle, but
take care not to dismantle the spacer tube
from the link rod.
4 The axle bracket bush must be removed for
renewal if it is worn or damaged.
5 Unscrew and remove the two retaining
bolts, then withdraw the valve and the link rod
from the mounting bracket.
Refitting
6 Where applicable, fit the new bush into the
axle bracket.
7 Relocate the valve on the mounting
bracket, and fit the retaining bolts.
8 Check that the brake pipe connections are
clean, then reconnect the pipes.
9 Smear the axle bush end of the link rod with
a small amount of general-purpose grease. Fit
the link rod into the bush, refit the washer, and
secure with the spring clip.
10 Top-up the fluid level in the master
cylinder reservoir, then bleed the brake
hydraulic system as described in Section 17.
If the original valve has been refitted, ensure
that the valve is held fully open whilst
bleeding. If a new valve has been fitted, the
bleed clip must be left in position whilst the
system is completely bled, then removed. The
valve will need to be adjusted as described in
the following Section.
26 Light-laden valve
(Van models) - adjustment
2
1 For this operation, the vehicle must be
raised for access underneath at the rear, but
must be standing on its wheels. Suitable
ramps (or an inspection pit) will therefore be
required. If positioning the vehicle on a pair of
ramps, chock the front roadwheels. The
vehicle must be empty, and the fuel tank no
more than half-full.
2 To adjust an original light-laden valve
linkage, grip the flats on the end of the rod to
prevent it from rotating, and turn the adjuster
nut to position the end face of the rubber seal
within the setting groove width (see
illustrations).
3 To adjust a new light-laden valve, rotate the
spacer tube to position the end face of the
rubber seal within the setting groove width,
then crimp over the end of the spacer tube
against the threaded rod flats (next to the
knurled section) (see illustration).
27 Anti-lock braking system
(ABS) - description
An anti-lock braking system is available on
certain models in the range. The system only
becomes operational over speeds in excess
of 7 mph (4 kph). It comprises an actuation
unit (servo unit and special tandem master
cylinder), a hydraulic unit, an ABS module,
and a sensor on each front wheel hub.
The hydraulic unit consists of a twin-circuit
electric pump which is controlled by a speed
sensor and modulator twin valve block (one
valve for each channel).
The module is located in the engine
compartment, and has four main functions: to
control the ABS system; to measure the
vehicle speed; to monitor the electric
components in the system; and to provide
“On-board” system diagnosis. The electrical
functions of the ABS module are continuously
monitored by two microprocessors, and these
also periodically check the solenoid-operated
valves by means of a test pulse during the
operation of the system. The module checks
the signals sent by the system sensors to
provide a means of fault diagnosis. In the
event of a fault occurring in the ABS system, a
warning light on the instrument panel will
come on and remain on until the ignition is
switched off. A particular fault is represented
by a two-digit code system stored within the
module memory. A “STAR” type tester is
required to read the fault diagnosis system, so
in the event of a fault being indicated, the
vehicle must be taken to a Ford garage for
analysis.
The ABS system functions as follows.
During normal braking, pressure from the
brake pedal (and the servo unit) closes the
master cylinder valves, and hydraulic pressure
is applied through the brake circuits in the
conventional manner. The rotational speed of
each front wheel is continuously monitored by
the system via the wheel sensors, and this is
compared to the vehicle speed information
being supplied from the speed sensor. When
a wheel is about to lock up, its rotational
speed drops more rapidly than the vehicle
speed, and when this condition is met, the
anti-lock side of the system cuts in. The
circuit inlet valve in the hydraulic unit is closed
off, to prevent further pressure being applied
through that circuit. In the event of this failing
to prevent excessive deceleration, the outlet
valve opens to reduce the pressure in that
circuit, thus preventing the wheel from locking
up. Both valves are then modulated on and off
(open and shut) to maintain the required
pressure in that circuit, to provide the
maximum possible hydraulic pressure (from
the master cylinder) without locking up the
wheel.
Slight pulsations will be felt through the
brake pedal when the anti-lock system cuts
in, and this is quite normal. To reduce
excessive brake pedal pulsations, a pedal
travel sensor monitors any slight increase in
9•18 Braking system
26.3 Light-laden valve adjustment on a
new valve showing the crimping point (A)
26.2B Light-laden valve linkage
adjustment on a used valve, showing
adjuster nut (A) and flats on the end of the
rod (B)
A
Spacer tube
B Rubber seal
C Setting groove
26.2A Light-laden valve linkage
adjustment
25.2 Brake pipe connections to the light-
laden valve