PARKING (SPRING) BRAKES WON'T RELEASE (Cont)

TM 9-2320-285-24-2

3-21. TREADLE VALVE AND BRAKE CONTROLS TROUBLESHOOTING (CONT)

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

PARKING (SPRING) BRAKES WON'T RELEASE (Cont)

If test gage indication is within 10 psi of AIR PRESS gage indication, proceed to step 3 below.

Step 3

Open drain cock on service air reservoir to relieve air system pressure.

Disconnect air brake tubing from elbow connector at emergency quick release valve (para 2-51a).

Install calibrated air pressure gage on tubing.

Close drain cock on service air reservoir.

Start engine and allow air system to charge to at least 60 psi pressure.

Pull PARKING BRAKE valve out fully.

Watch AIR PRESS gage and test gage indications.

If test pressure gage does not indicate zero psi immediately, repair or replace PARKING BRAKE

If test pressure gage immediately indicates zero psi, open service air reservoir drain cock to

relieve air system pressure. Then proceed to step 4 below.

Step 4

Disconnect hose from fitting at emergency port of one rear axle brake air chamber.

Install calibrated pressure gage on hose.

Close drain cock on service air reservoir.

Start engine and allow air system to build to at least 60 psi pressure.

Push PARKING BRAKE valve in fully.

Watch AIR PRESS gage and test gage indications.

If test gage indication differs from AIR PRESS gage indication by more than 10 psi, repair or

replace emergency quick release valve (para 3-24b).

If test gage indication is within 10 psi of AIR PRESS gage indication, proceed to step 5 below.

Step 5

Disconnect hose from fitting at emergency port of the other rear axle brake air chamber (see step 4

above).

Install calibrated pressure gage on hose.

Close drain cock on service air reservoir.

Start engine and allow air system to build to at least 60 psi pressure.

Push PARKING BRAKE valve in fully.

Watch AIR PRESS gage and test gage indications.

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