Carefully remove the old unit from the vehicle by disconnecting the
hydraulic lines, brackets and connections to the pedal. Place the old core in box of the
replacement unit, and return it to the store for your core credit.
Attach all mounting brackets and fittings from the old unit on the
replacement unit. Install on your vehicle in the same position as the old unit was
removed. Re-connect the hydraulic brake lines.
Do not remove any nut that is holding a cylinder or face plate to
install a bracket. You should install the bracket over the present nuts and secure with
Do not plug or bypass any hydraulic port on the unit. This could
substantially reduce the brake performance.
Warning: Brake bleeding instructions included must
be followed. Failure to follow this procedure will result in inefficient braking
Note: LOCATE AND ELIMINATE THE CAUSE OF
FAILURE BEFORE INSTALLING REPLACEMENT UNIT!
Dirt, sand or foreign material in the brake system is
responsible for most failures of original equipment units, and is a major cause of early
failure in replacement units. All old brake fluid should be flushed from the system. On
remote mounted boosters (units mounted underneath truck on frame) the master cylinder on
the firewall should be rebuilt and thoroughly cleaned, making sure that all sludge and
dirt are removed from the reservoir. If the old unit is not cleaned properly, the dirt
will be forced down into the booster during the first application of the brakes.
Gasoline and oil contamination are also major causes of
early failure in power brake units. If the vacuum hose runs directly from the engine down
to the booster, gasoline could enter the unit and destroy the rubber diaphragm. (See
"Caution Gasoline Danger" app. note.)
Special note: A major portion of all warranty returns are
the result of IMPROPER BLEEDING (not removing all of the air bubbles from the hydraulic
system), and IMPROPER BRAKE SHOE ADJUSTMENT.
TESTING POWER BRAKE ON VEHICLE
With the engine off, press the brake pedal several times to deplete all
vacuum reserve in system
Press the brake pedal and hold light foot pressure on the pedal. Start
the vehicle engine. If power brake is operating pedal will fall away under foot pressure
and less pressure is required to hold the pedal in the applied position. If no action is
felt when the engine is started, the power brake is not functioning.
Stop the engine. Again, deplete all reserve in the vacuum system. Press
the brake pedal and hold foot pressure on the pedal. If the pedal gradually falls away
under foot pressure, the hydraulic system is leaking.
If the brake pedal travels to within 1" of the floorboard, brake
shoes require adjustment.
Start the engine and run to medium speed, the turn off ignition.
Immediately close throttle to build up vacuum. Wait at least 90 seconds and then try brake
action. Two or more applications should be vacuum assisted. If not, vacuum check valve is
faulty or there is a leak in the vacuum system.
DO NOT RELEASE A VEHICLE UNTIL A FIRM BRAKE PEDAL IS OBTAINED
Road test the vehicle in a safe area by applying the brakes while
traveling about 20 mph to determine if the vehicle stops evenly and quickly. If the pedal
has a spongy feel, hydraulic system may contain air. Bleed the system thoroughly to remove
all air. (See "Troubleshooting
Guide app note.)