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TM 9-2330-326-14&P
H-29. TROUBLESHOOTING SPRING PARKING BRAKE
Points covered in this troubleshooting guide apply to service brake and spring parking brake
actuators. No effort is made to completely cover entire vehicle air brake system.
Insufficient Service Brake Application When Service Pedal is Depressed.
1.
Restricted air flow or low air pressure to service chamber.
2.
Worn brake lining or drums worn or cracked.
3.
Improper brake adjustment (auto or manual slack adjusters).
4.
Automatic adjusters not operating properly.
5.
Improper service pushrod-to-slack-adjuster alignment or geometry (refer to vehicle
manufacture's recommendations).
6.
Bent or broken cam brackets or chamber mounting brackets (cam brakes).
7.
Ruptured diaphragm.
8.
Air leak in lines, fittings, or valves and at actuator clamp ring.
9.
Improper pushrod length (not to vehicle manufacture's specifications).
Insufficient Spring Brake Application.
While most of the causes listed for "insufficient service brake application" will apply here, there are
additional items which should be checked.
1.
Broken power spring.
2.
Insufficient size of spring brake or improper output force.
3.
Spring brake was not fully released during brake adjustment.
Excessive Leakage --Service Brake Applied
1.
Leaking brake chamber diaphragm.
2.
Leaking hoses, tubes, or fittings.
3.
Faulty valves.
4.
Inspect for leakage at clamp ring. Tighten to 25-30 lb ft (33.895N.m40.674N.m) torque if
leakage is found.
Excessive Leakage --Spring Brakes Released By Air
1.
Leaking diaphragm or main seal in spring section.
2.
Leaking pushrod seal.
3.
Leaking hoses, tubes, or fittings.



 


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