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BRAKES
2G-21
system, use Jeep Brake Fluid or equivalent grade
marked SAE J1703 or DOT 3 only. Do not use any brake
fluid that does not have these grade markings. The use
of nonapproved fluids can result in low fluid levels,
spongy pedal, fluid aeration, brake fade, and deteriora-
tion of brake system components.
CAUTION: Never refill or add used or reclaimed brake
fluid to the hydraulic
system.
BRAKE FLUID LEVEL
The master cylinder fluid level should be checked at
least four times a year or every 5,000 miles (8 046 km).
Refer to the Maintenance Schedule for details.
When refilling or adding fluid to the system, fill the
master cylinder fluid reservoirs to within 1/4 inch (6.35
mm) of each reservoir rim. This is the proper fluid level
for all Jeep vehicles.
When checking the fluid level, also inspect the rubber
diaphragm seal on the cylinder cover for cracks, cuts,
distortion, or any other condition that might allow air or
foreign material to enter the master cylinder reservoirs.
In addition, when the cover is removed for any reason,
do not allow the seal to contact dirt, grease, or other
foreign material which could be transferred to the fluid
reservoirs.
HYDRAULIC
SYSTEI
INSPECTION
(1) Clean master cylinder and cylinder cover thor-
oughly before checking fluid level.
(2) Check master cylinder cover retaining spring for
proper tension and fit. Spring should provide enough
tension on cover to maintain airtight seal.
(3) Remove cylinder cover and inspect cover and
rubber diaphragm seal for cracks and distortion.
(4) Check master cylinder fill level.
(5) Check for dirt and foreign material in reser-
voirs. If fluid contamination is suspected, drain fluid
sample into clean glass container and test for con-
tamination as evidenced by fluid layering.
(6) Inspect all fittings and brake lines for leakage,
kinks, or other damage.
(7) Inspect condition of front brake hoses. Replace
hoses if cut, cracked, swollen, or leaking.
(8) Check for evidence of fluid leakage at rear wheel
cylinders and front calipers. Repair as necessary.
MASTER CYLINDER
A dual reservoir master cylinder is used on all Jeep
vehicles. The hydraulic system for the front brakes is
completely separate from the rear brakes. In the event
of hydraulic brake failure in the front system, the rear
hydraulic brakes will still operate. If a failure occurs in
the rear brakes, the front brakes will still operate.
The dual master cylinder has two outlet ports, two
fluid reservoirs, and two hydraulic pistons which are
operated in tandem by a single push rod.
When the master cylinder fluid reservoirs are filled
and the front and rear brake systems purged of air,
there is a solid column of fluid on the forward side of
both the primary and secondary pistons.
During brake application, fluid is displaced by the
master cylinder pistons into the front caliper and rear
wheel cylinders to activate the brakes. At brake release,
fluid returns from the calipers and wheel cylinders to
the master cylinder reservoirs.
Master Cyllnier Service—AH Models
Removal
(1) Disconnect brake lines at master cylinder. Cap
or tape outlet ports in master cylinder and open ends of
brake lines to prevent entry of dirt.
(2) On models with nonpower brakes, disconnect
master cylinder push rod at brake pedal.
(3) Remove bolts or nuts attaching master cylinder
to dash panel or power unit and remove master cylinder.
Disassembly
(1) Remove cover and diaphragm seal and drain
fluid from master cylinder. Mount master cylinder in
vise.
(2) On models with power brakes, push primary
piston inward using wooden dowel and remove piston
snap ring (fig. 2G-9 and 2G-10).
(3) On CJ models with nonpower brakes, slide boot
to rear of push rod. Push primary piston inward (with
push rod) and unseat piston snap ring. Remove push
rod, boot, snap ring, washer, and push rod retainer as
assembly (fig. 2G-9).
(4) Remove and discard primary piston assembly. It
is not necessary to disassemble primary piston. It is
supplied as completer assembly in overhaul kit.
(5) Remove secondary piston assembly. To ease pis-
ton removal, apply compressed air through compensator
port in front reservoir.
(6) Remove and discard piston seal and piston cups
from secondary piston.
(7) Clean and inspect master cylinder. Replace unit
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Troubleshooting
