TM 5-3805-254-20-1
ORGANIZATIONAL TROUBLESHOOTING - CONTINUED
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
70.
PARKING BRAKE DOES NOT RELEASE - CONTINUED.
Step 2.
Check four airbrake chambers (1) for air leaks as follows: have assistant release and apply
PARKING BRAKE control knob (2) several times. Check each individual airbrake chamber (1) for
air leaks.
a. If one or more airbrake chambers (1) are leaking, defective airbrake chamber must be
replaced. Notify Direct Support Maintenance.
b. If four airbrake chambers (1) are not leaking, go to step 3.
Step 3.
Check PARKING BRAKE control valve (3) for input air pressure as follows: pull PARKING BRAKE
control knob (2) out to apply parking brakes. Using 5/8-inch open-end wrench, loosen input hose
fitting (4) six turns. Push in PARKING BRAKE control knob (2), and listen for hissing noise.
a. If hissing noise is not heard, go to step 4.
b. If hissing noise is heard, pull out PARKING BRAKE control knob (2). Tighten input
hose fitting (4), using 518-inch open-end wrench. Go to step 5.
Step 4.
Check double check valve (5) for output air pressure as follows: using 5/8-inch open-end wrench,
loosen output hose fitting (6) six turns. Listen for hissing noise.
a. If hissing noise is not heard, notify Direct Support Maintenance.
b. If hissing noise is heard, replace air line (7), (page 2-1025). Go to step 5.
Step 5.
Check PARKING BRAKE control valve (3) for output air pressure as follows: pull PARKING BRAKE
control knob (2) out to apply parking brakes. Using 518-inch open-end wrench, loosen output hose
fitting (8) six turns. Push in PARKING BRAKE control knob (2) and listen for hissing noise.
a. If hissing noise is not heard, defective PARKING BRAKE control valve (3) must be
replaced. Notify Direct Support Maintenance.
b. If hissing noise is heard, go to step 6.
Step 6.
Check double check valve (9) for output air pressure as follows: using 3/4-inch open-end wrench,
loosen output hose fitting (10) six turns. Have assistant push in PARKING BRAKE control knob (2).
Listen for hissing noise.
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