Low Air Indicator. Compressor and Belt or Belts. Compressor Operation. Air pressure shall be reduced to 50 psi and the engine started and operated at approximately 1200 rpm. Air Leakage. Inspection for leakage shall be conducted with a fully charged system and brakes fully applied. Air Reserve. Air Reservoir and Valves. Parking and Emergency Brake Application. Vehicles with original equipment air-operated parking brakes are permissible. There are different systems designed for automatic or manual operation of the system as the design allows (check automatic application of brakes when air tanks are being drained). Gladhands and Air System. Brake Mechanical Components. Do not attempt to dismantle a double diaphragm spring brake unit while it is on the vehicle. Utilize a safety cage and remove the entire unit from the vehicle. Replace with a new or rebuilt assembly. When rebuilding or overhauling a brake chamber, strict adherence to manufacturer's procedures is required. Inspect brake chamber for: Slack Adjuster (Push Rod) Travel. With the assistance of a second party, make a treadle valve application at 85 psi in system and note rod travel. Wedge Brake. With the assistance of a second party, make a full brake application. Brake Camshafts. Brake Linings—Air Brakes. Visually inspect brake shoes. If shoes cannot be seen, removal of the lower portion of the dust cover is required. Brake Drums Air Brakes. Disc Brakes—Air.