COMPRESSED AIR AND BRAKE SYSTEM OPERATION (Contd)
SPRING BRAKE RELEASE CONTROL VALVE - This valve functions as an override when a failure in the air
supply system (causing spring brakes to engage) occurs. When valve is manually pushed in, emergency air is
supplied to the spring brake chambers. This releases the spring brakes, allowing vehicle movement.
PEDAL VALVE - Vents primary or secondary signal air pressure when pedal is released.
FRONT BRAKE CHAMBER VENT - Vents air pressure inside chambers when pedal valve is released.
LIMITING VALVE - Vents signal air pressure going to front brake chambers so rear brakes apply first.
STEP BOX QUICK-RELEASE VALVE - Vents air pressure from spring brake chambers when parking brake valve
has been actuated.
REAR BRAKE CHAMBERS - Vents ports on chambers to prevent air pressure build-up.
RELAY VALVES - Vents air pressure in rear brake chambers directly to intake tube when brake pedal is released.
Vents signal air pressure through upper port in valve.
AIR INTAKE STACK - Venting point for the vent system.
TRANSMISSION VENT - Vents internal air pressure build-up due to internal heat.
SPRING PARKING BRAKE VALVE - Vents air pressure from air and doublecheck valves #3 and #4.
TRANSFER CASE VENT - Vents internal air pressure build-up due to internal heat.
FUEL TANK VENTS - Vent fuel vapors to prevent partial vacuum from stopping fuel flow.