Split-System Air Loss Diagnostics & Check Valve Verification
Split-System Air Loss Diagnostics & Check Valve Verification
Classification: Official Technical Position & Field Procedure
Regulatory Standards: CFR 2021 Title 49 | Bendix BW1114 Integrity Guidelines
Air System Performance Stance
It is the official stance of Battle Motors that all production chassis strictly comply with split-system air safeguarding regulations. If a single reservoir circuit experiences a sudden, catastrophic loss of pressure, the remaining circuit must stay automatically isolated and fully pressurized to guarantee vehicle stopping control.
During standard service testing, restrictive manual tank petcocks often bleed air too slowly, causing the internal shuttle disc of the Sealco 7200 two-way check valve to float in the middle and bleed both circuits down equally. This creates a false indication of a system failure. The procedure below outlines the mandatory, uniform method for correctly isolating and verifying check valve operation.
Subsection 10.2-A: Check Valve Isolation Test Procedure
- Step 1: System Charging
- Step 2: Temporary High-Flow Test Plumbing
- Step 3: Snap-Drop Execution
- Step 4: Gauge Verification
- Step 5: Dynamic Isolation Window
Chock the wheels. Start the vehicle and charge the air system until it reaches governor cut-out pressure (120–130 psi). Shut the engine completely off, but turn the ignition key back to the ON/RUN position to keep the dash gauges active and ensure the low-air warning buzzer can sound.
To bypass restrictive production drain lines and simulate a true gross leak that forces the shuttle valve to snap over and lock out, you must temporarily install a high-flow, $\frac{1}{2}$-inch quarter-turn ball valve into an open port on the reservoir being tested.
Application Note: Because tank layouts, routing, and available ports vary by chassis model, the exact location and plumbing required to hook up the test ball valve will be unique to each vehicle configuration.
Snap the temporary quarter-turn ball valve completely open instantly. This immediate, high-velocity blast of escaping air creates the sharp pressure drop required to force the Sealco shuttle disc to slide and seal off the leaking side.
Watch your dual dash needles. The failed tank will instantly drop to zero, and the low-air warning buzzer will sound. The companion tank must hold steady.
Leave the dump valve wide open and watch the good tank for 1 minute. If the companion circuit holds its air without dropping, the check valves are working properly. Close your test valve, restart the engine, rebuild pressure, and mirror the exact same process on the opposite tank.
Mandatory Post-Test Reassembly & Liability Release
Once testing is completed, the air system must be completely returned to normal before the vehicle is released for operation.
The performing facility and servicing technician assume sole responsibility for the complete removal of all temporary testing hardware and the proper reinstallation of original components. Battle Motors assumes no liability for damages, injuries, or system failures resulting from a failure to restore the vehicle to its exact factory-approved layout.
- Hardware Removal: Remove all temporary high-flow test ball valves and diagnostic lines from the chassis. Do not leave test hardware installed.
- Port Restoration: Reinstall all original factory tank plugs, fittings, or moisture ejectors into their factory ports.
- Final Configuration Check: The vehicle must be returned to its exact as-built configuration and verified completely leak-free. Successful return to the original as-built configuration completely releases Battle Motors from any and all liability connected to, or arising from, the execution of this testing procedure.
Required Reference Documentation
For specific chassis air schematics, port locations, and foundational regulatory data, technicians must reference the following publications:
- CFR 2021 Title 49 (Federal Motor Carrier Safety Administration standards for air system safeguarding)
- Bendix BW1114 (Air Brake System Troubleshooting & Integrity Guide)
- Battle Motors Service Manual (Chassis-specific air system routing and tank port specifications)