Safety comes first. This general guide does not determine whether a specific vehicle is safe to operate. Follow vehicle, carrier, cargo, facility, and public-safety instructions.
Do not normalize an air warning
Slow pressure build, repeated low-air warnings, rapid pressure loss, brakes that will not release, or a continuous leak can indicate an unsafe brake or supply-system condition. Park in a safe location and follow the vehicle and company procedures.
Record what the gauges do
- Primary and secondary pressure before start
- How long pressure takes to build
- Maximum pressure reached
- Pressure change with engine off and brakes released
- Pressure change during brake applications
- Any low-air warning or parking-brake behavior
Locate the sound safely
From a safe standing position, note whether the leak appears near the tractor, gladhands, front or rear trailer, suspension, tanks, dryer, valves, or a wheel. Never crawl under an unsupported vehicle or enter traffic to locate a leak.
Useful dispatch details
- Truck and trailer type and unit numbers
- Whether the trailer is loaded
- Whether brakes release or drag
- Any recent freeze, repair, coupling, or trailer swap
- Exact safe work location
- Photos or video recorded without approaching traffic
When the unit should not move
Do not drive when required air pressure cannot be maintained, brake performance is uncertain, a brake is dragging or overheated, a chamber or line is damaged, or a qualified repair professional has not determined that movement is safe.