TM 5-3805-254-20-1
ORGANIZATIONAL TROUBLESHOOTING - CONTINUED
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
66.
AIR BRAKES DO NOT RELEASE.
WARNING
Safety goggles must be worn when working with air lines to prevent personal injury.
Step 1. Start engine and check that air pressure in air system is between 90 and 130 psi (TM 5-3805-254-
10). Shut down engine (TM 5-3805-254-10).
a.
If air pressure is not between 90 and 130 psi, go to Malfunction 64, AIR PRESSURE
DOES NOT EXCEED 90 PSI (page 2-339).
b.
If air pressure is between 90 and 130 psi, go to step 2.
WARNING
Ensure that vehicle is on level ground and that rear wheels are chocked to prevent vehicle from
moving or severe injury to personnel may result.
Step 2. Chock rear wheels of truck. Check PARKING BRAKE control valve (3) for air pressure as follows:
pull knob (1) out to apply parking brakes. Using 5/8-inch open-end wrench, loosen output hose
fitting (2) six turns, push in knob (1) and listen for hissing noise.
a.If hissing noise is not heard, replace PARKING BRAKE control valve (3) and notify
Direct Support Maintenance.
b.If hissing noise is heard, pull out handle (1) to apply brakes. Tighten output hose
fitting (2) using 518-inch open-end wrench, and go to step 3.
Step 3. Check treadle valve (4) for air pressure as follows: have assistant press down brake pedal (5) and
release. Check for exhaust of air pressure from valve vent (6) on bottom of treadle valve (4)
when brake pedal (5) is released.
a.If air pressure is not vented from valve vent (6) on bottom of treadle valve (4), go to
step 4.
b.If air pressure is vented from valve vent (6) on bottom of treadle valve (4), go to step
5.
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