length FORD SIERRA 1985 1.G Braking System Workshop Manual

Torque wrench settingsNmlbf ft
Caliper carrier bracket-to-hub carrier bolts . . . . . . . . . . . . . . . . . . . . . .51 to 6138 to 45
Front caliper guide bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20 to 2515 to 18
Rear caliper guide bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31 to 3523 to 26
Rear brake backplate nuts - P100 models . . . . . . . . . . . . . . . . . . . . . . .45 to 5433 to 40
Servo-to-bulkhead nuts (conventional braking system) . . . . . . . . . . . . .35 to 4526 to 33
Master cylinder-to-servo nuts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20 to 2515 to 18
Hydraulic unit-to-bulkhead nuts (ABS) . . . . . . . . . . . . . . . . . . . . . . . . . .41 to 5130 to 38
Hydraulic unit accumulator (ABS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34 to 4625 to 34
Pump mounting bolt (ABS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7 to 95 to 7
High pressure hose-to-pump union (ABS) . . . . . . . . . . . . . . . . . . . . . . .7 to 125 to 9
Wheel sensor mounting bolts (ABS) . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 to 116 to 8
General information
The braking system is of the dual circuit
hydraulic type. The front and rear circuits are
operated independently from a tandem
master cylinder, so that in the event of a
hydraulic failure in one circuit, full braking
force will still be available to two wheels
through the remaining circuit.
A deceleration sensitive valve on Saloon,
Hatchback and Estate models not fitted with
an Anti-lock Braking System (ABS), and a load
apportioning valve on P100 models, is
incorporated in the rear brake hydraulic
circuit. The valve regulates the pressure
applied to the rear brakes and reduces the
possibility of the rear wheels locking under
heavy braking.
All models are fitted with front disc brakes,
with solid or ventilated discs depending on
model. The calipers are of single piston sliding
type, which ensures that equal pressure is
applied to each disc pad.
Non-ABS models are fitted with rear disc
brakes or rear drum brakes, incorporating
leading and trailing shoes operated by
double-acting wheel cylinders. A self-adjuster
mechanism is fitted which consists of a
toothed quadrant which is kept in contact with
a toothed pin attached to the shoe strut by
means of a spring. The quadrant incorporates
an arm which locates in a slot in the leading
shoe. As the shoe linings wear the quadrant is
pulled from the pin when the footbrake is
operated, and automatically repositioned to
effectively lengthen the shoe strut.
ABS is available as an option for all models
except the P100. The system comprises an
electronic control unit, roadwheel sensors,
hydraulic actuator with electrically-driven
hydraulic pump, and the necessary valves and
switches. Disc brakes are fitted to all four
wheels. The front disc brakes are similar to
those fitted to non-ABS models, but the rear
brakes incorporate a self-adjusting
mechanism, and a mechanical handbrake
mechanism. The purpose of the system is to
prevent wheel(s) locking during heavy brake
applications. This is achieved by automatic
release of the brake on the locked wheel,followed by reapplication of the brake. This
procedure is carried out four times per second
by the control valves in the valve block. The
valves are controlled by the electronic control
unit which itself receives signals from the
wheel sensors, which monitor the locked or
unlocked state of the wheels. A pressure
regulating valve is incorporated in the rear
hydraulic circuit to maintain the desired
pressure ratio between the front and rear
circuits.
Precautions
Note: Hydraulic fluid is poisonous; wash off
immediately and thoroughly in the case of skin
contact and seek immediate medical advice if
any fluid is swallowed or gets into the eyes.
Certain types of hydraulic fluid are
inflammable and may ignite when allowed into
contact with hot components; when servicing
any hydraulic system it is safest to assume
that the fluid is inflammable and to take
precautions against the risk of fire as though it
is petrol that is being handled. Hydraulic fluid
is also an effective paint stripper and will
attack plastics; if any is spilt, it should be
washed off immediately using copious
quantities of fresh water. Finally, it is
hygroscopic (it absorbs moisture from the air)
old fluid may be contaminated and unfit for
further use. When topping-up or renewing the
fluid, always use the recommended type and
ensure that it comes from a freshly-opened
sealed container
Note: When working on the brake
components, take care not to disperse brake
dust into the air, or to inhale it, since it may
contain asbestos which is injurious to health.
General
1If any of the hydraulic components in the
braking system have been removed or
disconnected, or if the fluid level in the
reservoir has been allowed to fall appreciably,
it is inevitable that air will have been
introduced into the system. The removal of all
this air from the hydraulic system is essential
if the brakes are to function correctly, and the
process of removing it is known as bleeding.
2Where an operation has only affected one
circuit (front or rear) of the hydraulic system,
then it will only be necessary to bleed the
relevant circuit. If the master cylinder has
been disconnected and reconnected, or the
fluid level has been allowed to fall
appreciably, then the complete system must
be bled.
3One of three methods can be used to bleed
the system.
Bleeding
Two-man method
4Gather together a clean jar and a length of
rubber or plastic bleed tubing which will fit the
bleed screws tightly. The help of an assistant
will be required.
5Remove the dust cap where fitted, and
clean around the bleed screw on the relevant
caliper or wheel cylinder, then attach the
bleed tube to the screw (see illustration). If
the complete system is being bled, start at the
front left-hand caliper.
6Check that the fluid reservoir is topped up
and then destroy the vacuum in the brake
servo by giving several applications of the
brake pedal.
7Immerse the open end of the bleed tube in
the jar which should contain two or three
inches of hydraulic fluid. The jar should be
positioned about 300 mm (12.0 in) above the
bleedscrew to prevent any possibility of air
entering the system down the threads of the
bleed screw when it is slackened.
2Brake hydraulic system
(conventional braking system)
- bleeding1General information and
precautions
10•2Braking system
2.5 Removing the dust cap from a wheel
cylinder bleed screw
Caution: Refer to the
precautions in Section 1.