6
ANTILOCK RE-APPLY
If the antilock controller senses that wheel speed has
increased sufficiently to require reapplication of braking
pressure, it de-energizes the supply and exhaust solenoids.
With both solenoids de-energized, the modulator re-applies
air to the brakes in the same manner it did during a non-
antilock application.
PREVENTIVE MAINTENANCE
GENERAL
Perform the tests and inspections presented at the
prescribed intervals. If the modulator fails to function as
described, or leakage is excessive, it should be replaced
with a new or genuine Bendix remanufactured unit, available
at any authorized parts outlet.
EVERY 3 MONTHS, 25,000 MILES OR 900
OPERATING HOURS
1. Remove any accumulated contaminates and visually
inspect the exterior for excessive corrosion and physical
damage.
2. Inspect all air lines and wire harnesses connected to
the modulator for signs of wear or physical damage.
Replace as necessary.
3. Test air line fittings for excessive leakage and tighten or
replace as necessary.
4. Perform the ROUTINE OPERATION AND LEAKAGE
TESTING described in this manual.
OPERATION & LEAKAGE TESTS
LEAKAGE TESTING
1. Park the vehicle on a level surface and block or chock
the wheels. Release the parking brakes and build the
air system to full pressure.
2. Turn the engine OFF and make 4 or 5 brake applications
and note that the service brakes apply and release
promptly.
3. Build system pressure to governor cut-out and turn the
engine OFF.
4. Make and hold a full service brake application.
A. Apply a soap solution to the exhaust port of the modu-
lator. Leakage should not exceed a 1" bubble in less
than 3 seconds. If leakage exceeds the specified maxi-
mum, replace the modulator.
B. Apply a soap solution around the solenoid assembly
(top and bottom). Leakage should not exceed a 1" bubble
in less than 3 seconds. If leakage exceeds the speci-
fied maximum, tighten the solenoid cap screws and
re-test. If the leakage remains excessive after re-test-
ing, replace the modulator.
FIGURE 7 -
M-21
™
, M-22
™
MODULATOR ANTILOCK EXHAUST OF BRAKES
BRAKE VALVE
SPRING
SUPPLY
DIAPHRAGM
SUPPLY
SOLENOID
SPRING
EXHAUST
DIAPHRAGM
EXHAUST
SOLENOID
BRAKE
CHAMBER
EXHAUST PORT
