Diesel Air Brake System

Diesel Air Brakes are needed in order to handle the extreme loads that the vehicle carries. If hydraulics were used for the tractor trailer combination, the heat would boil the fluid and cause a catastophic failure of the brake system. 
One tip to Keep in mind is that, just as air in a hydraulic system is a problem, so is water in the Air System. It can shorten air brake resevoir capacity as well as freeze in cold temperatures and cause a failure of some of the valves in the system.

Here is some information on how Diesel Air Brakes work. 

                            Diesel Primary Circuit Operation

                          Diesel Secondary Circuit Operation

Diesel Air Brake System Components