Wheel Cylinder - Jeep 1979 CJ-5 Technical & Service Manual

BRAKES 28-23
S E C O N D A R Y
PISTON ASSEMBLY
6 0 2 4 0
Fig. 21-10 Master Cylinder
Cherokee-Wagoneer-Truok Models
Assembly
(1) Install replacement tube seats (if removed) us-
ing spare tube fitting nuts to press seats into place. Do
not allow seats to become cocked during installation. Be
sure seats are bottomed. Remove tube fitting nuts and
check for burrs or chips. Remove burrs or chips. Rinse
master cylinder in brake cleaning solvent and blow out
all passages with compressed air.
(2) Install piston cups on secondary piston. Piston
cup installed in groove at end of piston should have lip
facing away from piston. Install next cup so lip faces
piston (fig. 2G-9 and 2G-10).
(3) Install seal protector, piston seal, spring re-
tainer, and return spring on secondary piston (fig. 2G-9
and 2G-10). Install piston seal so lip faces interior of
master cylinder bore when assembly is installed. Be
sure return spring seats against retainer and that re-
tainer is located inside lip of piston seal.
(4) Lubricate master cylinder bore and secondary
piston seal and cups with clean brake fluid and install
secondary piston assembly in cylinder bore.
(5) Lubricate seals on new primary piston assembly
with clean brake fluid and install assembly in master
cylinder bore.
(6) On models with power brakes, press primary
piston inward using wooden dowel and install piston
snap ring in groove of master cylinder bore.
(7) On CJ models with nonpower brakes, press
primary piston inward (using push rod) and install pis-
ton snap ring in groove of master cylinder bore.
(8) On CJ models with nonpower brakes, install
boot if removed.
(9) Install replacement diaphragm seal on master
cylinder cover.
Installation
(1) Position master cylinder on dash panel or power
unit and install attaching nuts and washers. Tighten
nuts to 30 foot-pounds (41 N»m) torque.
(2) Connect brake lines to master cylinder.
(3) Fill master cylinder reservoirs to within 1/4
inch (6.35 mm) of rim with Jeep Brake Fluid or equiva-
lent grade marked SAE J-1703 or DOT 3.
(4) Install cover and diaphragm seal.
(5) On models with nonpower brakes, connect push
rod to brake pedal.
(6) Bleed entire brake system as outlined under
Brake Bleeding.
WHEEL CYLINDER
The rear drum brake wheel cylinder consists of a cast
iron housing with a piston bore machined in it. Two
opposed pistons, rubber piston cups, and a compression
spring with integral cup expanders are contained within
the piston bore (fig. 2G-11). Rubber dust boots are in-
stalled at each end of the cylinder to prevent entry of
dirt and water. Each cylinder is equipped with a bleeder
screw to facilitate brake bleeding.
The compression spring is used to hold the piston cups
tightly against the pistons and the integral cup expan-
ders hold the piston cups tightly against the walls of the
piston bore. The expanders prevent air from being
drawn past the cups and into the hydraulic system when
the brakes are released.
Remowal
(1) Remove wheels, brakedrums, and brakeshoes.
Refer to Drum Brake Section for procedure.
(2) Disconnect brake line at wheel cylinder. Do not
bend line away from cylinder. When cylinder is re-
moved, line will separate from cylinder easily.
(3) Remove cylinder-to-support plate bolts and re-
move cylinder.
Overhaul
(1) Remove brakeshoe links and dust boots.
(2) Push pistons, piston cups, and compression
spring and expanders out of piston bore. Discard piston
cups, they are not reusable.
(3) Clean all cylinder components using brake
cleaning solvent or brake fluid only.