Air Brake Inspecting and Leakage Testing
Important: There is no scheduled (Bendix) air valve maintenance that requires disassembly of the valve within the warranty period. If the valve does not function while within the warranty period, do not disassemble the part as this will void the warranty.
If any of the tests in the following procedure fail, see of the S2 Chassis Workshop Manual to test individual air brake components and valves.
Warning: Some steps in this operation require the parking brakes to be released. Make sure the vehicle is on a level surface and all tires are chocked. Failure to do so could result in the vehicle rolling, causing personal injury and/or vehicle damage.
- Park the vehicle on a level surface, shut down the engine, apply the parking brake, and chock all tires.
- Completely drain all air reservoirs.
- Install accurate test gauges in the primary and secondary reservoirs.
- Start the engine and run it at a fast idle.
- Record reservoir pressures when the low-pressure warning turns off.
- Record governor cut-out pressure and air dryer purge pressure.
- Reduce service air pressure by applying and releasing the service brakes several times, and record governor cut-in pressure.
- Charge the air system to governor cut-out, shut down the engine, and apply the parking brakes.
- Allow pressure to stabilize for one minute.
- Observe the installed service reservoir gauges. The pressure should not drop more than 10 psi (69 kPa) within five minutes.
- If necessary, start the engine and charge the air system. Shut down the engine and release the parking brakes.
- Make and hold a full service brake application, allowing the pressure to stabilize for one minute. Observe the installed service reservoir gauges. The pressure should not drop more than 15 psi (103 kPa) in five minutes.
- With the air system at full pressure and the engine idling, operate the parking brake control valve and note that all spring brake chambers apply and release the parking brake promptly as the control valve knob is pulled out and pushed in.
- Build air system pressure to cut-out and shut down the engine.
- Completely drain the secondary (front axle) reservoir. On vehicles equipped with single check valves, where the air dryer is not attached to the reservoir, the primary reservoir should not lose pressure.
- Make a service brake application. The rear axle brakes should apply and release and the brake lights should illuminate.
- Close the drain cocks, recharge the system, and completely drain the primary reservoir. On vehicles equipped with single check valves, where the air dryer is not attached to the reservoir, the secondary reservoir should not lose air pressure.
- Start the engine and charge the air system until the governor cuts out.
- Shut down the engine and leave the parking brake released.
- Completely drain the primary reservoir.
- Make a modulated service brake application. Both front and rear brakes should modulate. At a steady full brake application, pressure should not drop more than 10 psi (69 kPa) within five minutes.
- Drain all reservoirs, then remove the gauges from the service reservoirs. Close the reservoir drain cocks.
- Remove the chocks from the tires.