Simple Straight Truck Air Brake Diagram. If a spring brake is leaking from the the spring brake to the service brake side that air will travel back up the service line and out the exhaust of the next valve back. Air brake system truck tractor there are basic differences between straight truck and truck tractor air systems.

Must complete an air brake practical test. Spring brake modulating valve where applicable usually found on the spring brake relay valve straight trucks and buses if the automatic slack adjuster is not adjusting repair or replace it to obtain desired setting. Parts of an air brake diagram the design of any air brake valve is more easily understood by recognizing some major components and parts.

The system must be pressurized with air before the brakes will release at rest the brakes remain engaged.

Air brake systems and devices. Parts of an air brake diagram the design of any air brake valve is more easily understood by recognizing some major components and parts. Must complete an air brake practical test. Note not all valves have all the components shown and described in this booklet.