Parking Brake - Ford Mercury Colony 1968 Shop Manual

2-14 GROUP 2 - Brakes
inders. The wheel cylinder pistons, in
turn, convert hydraulic pressure back
into physical force at the brake shoes.
The self-adjusting brake mecha-
nism consists of a cable, cable guide,
adjusting lever, and adjuster spring
(Fig. 8). The cable is hooked over
the anchor pin at the top and is con-
nected to the lever at the bottom. The
cable is routed along the webb of the
secondary brake shoe by means of the
cable guide. The adjuster spring is
hooked to the primary brake shoe and
to the lever. The automatic adjuster
operates only when the the brakes are
applied while the vehicle is moving
rearward and only when the secondary
shoe is free to move toward the drum
beyond a predetermined point.
With the vehcile moving rearward
and the brakes applied the wrap-
around action of the shoes following
the drum forces the upper end of the
primary shoe against the anchor pin.
The action of the wheel cylinder
moves the upper end of the secondary
show away from the anchor pin. The
movement of the secondary shoe
causes the cable to pull the adjusting
lever upward and against the end of
a toothe on the adjusting screw star-
wheel. The upward travel of the lever
increased as lining wear increases.
When the lever can move upward far
enough, it passes over the end of the
tooth and engages the tooth. When
the brakes are released, the adjusting
spring pulls the lever downward
causing the star-wheel to turn and
expand the shoes. The star-wheel is
turned one tooth at a time as the lin-
ings progressively wear.
With the vehicle moving forward
and the brakes applied, the secondary
shoe is against the anchor pin and the
primary shoe is moved toward the
drum. "Therefore, the adjuster does
not operate.
The rear brake assembly is basical-
ly the same as the front brake. The
conventional parking brake lever,
link, and spring are used in the rear
brake.
The anchor pins on all brakes are
fixed and non-adjustable.
BRAKE BOOSTER SYSTEM
This diaphragm type brake booster
is a self contained vacuum-hydraulic
braking unit mounted on the engine
side of the dash panel.
The brake booster is of the vacuum
suspended type which utilizes engine
intake manifold vacuum and atmos-
pheric pressure for its power.
Adjustment of the push rod is the
only service permitted on the brake
booster. The booster unit is to be ex-
changed when it is inspected, checked
and found to be defective.
PARKING BRAKE
An independent foot-operated park-
ing brake control actuates the rear
wheel brake shoes through a cable
linkage. The operating cable is routed
from the parking brake control as-
sembly to the equalizer. The rear
brake cables connect the equalizer
assembly to the parking brake lever
at each rear secondary shoe (Fig. 8).
Two types of brake pedal control
are used. The automatic (vacuum)
release type (Fig. 9) is used on the
Mercury Parklane. All other models
use the manual release type (Fig. 10).
When the pedal is depressed (either
manual or automatic release type) the
secondary brake shoes are forced
against the rear brake drums. The
pedal is held in the applied position
by the engagement of a spring-loaded
pawl with a ratchet in the control as-
sembly (Figs. 9 and 10).
Either type of parking brake con-
trol assembly is mounted to the dash
panel and the instrument panel. The
pedal, pivots on a stationary pedal
mount. A spring-loaded pawl and a
release lever are assembled to the
pedal. A ratchet is assembled to the
upper end of the pedal. The pawl con-
tacts the ratchet at such an angle that
the ratchet teeth will slide over the
pawl as the pedal is depressed; how-
ever, when the applying motion stops
and the pedal starts to release, the
pawl engages the ratchet and thus
locks the brakes in the applied posi-
tion.
When the lever is pulled back on
the manual release type (Fig. 10), the
cam action of the lever on the pawl
cam pin will disengage the pawl from
the ratchet to release the brakes.
On the automatic type, the vacuum
power unit will release the parking
brakes automatically when the trans-
mission selector lever is moved into
any drive position with the engine
running. The brakes will not release
automatically, however, when the
selector lever is in the neutral or
-VACUUM POWER UNIT
PAWL (UPPER END)
PISTON ROD
REVERSE LEVER
PEDAL MOUNT
CABLE CLEVIS
H1350-A
FIG. 9—Parking Brake Control Assembly with Automatic Release