Defect Found Mid-Run: Brake Chamber Leak

Symptoms:

• Hiss at a brake chamber indicates an air leak - a failed diaphragm, a loose fitting, or a cracked chamber. A leaking chamber means that wheel's brake may not apply fully or may drag.
• Oil stain on the inside of the tyre is significant. Oil/grease on the inner tyre wall near a brake can come from a failed wheel seal or from a brake component leaking. Either way, it indicates a mechanical defect in that wheel-end/brake assembly, and oil contamination on a tyre is itself a safety issue (reduced friction, potential tyre degradation).
• Gauge at 800 kPa and no warning does not mean the system is sound. A single chamber leak may be small enough that the compressor keeps up at idle, but it will worsen under braking demand and heat.

Roadworthiness: A leaking brake chamber is a brake system defect and the vehicle is not roadworthy for continued operation at 42 t. The relevant question is not whether it will fail in the next 40 km, but whether it meets the standard now - it does not. The correct classification is a major defect requiring repair before further travel.

Stop where you are and arrange repair; do not drive to the workshop.

Option A - continue 40 km: Rejected. A leaking chamber plus oil contamination is a developing brake failure. Under braking on the route, the leak worsens, pressure recovery may not keep pace, and braking becomes asymmetric - a pulling or dragging brake can destabilise a 42 t combination, especially in an emergency stop. The 3-hour delivery window is not a reason to drive an unroadworthy vehicle; schedule pressure is exactly the kind of coercion chain-of-responsibility rules are designed to resist.

Option B - return 5 km to the roadhouse: Better than continuing, but still involves driving a defective vehicle. Only justified if the roadhouse offers a safe place to wait and the 5 km can be done at low speed without brake demand. Even then, it is a compromise, not a fix.

Option C - stop where you are (selected): The safest option if you are in a safe stopping position off the carriageway. Secure the vehicle, apply the park brake, chock if needed, place warning devices, and call for a mobile mechanic or recovery. A 150 km call-out is an inconvenience; a brake failure at 42 t is a catastrophe.

Practical step: notify the operator immediately, explain the defect and the delay, and let them manage the customer. Do not let the delivery window drive the decision.

Records and reporting:

1. Defect record: describe the hiss location, the oil stain, gauge reading, time, odometer, and the decision to stop. Classify it as a major brake defect.
2. Notify the operator promptly so the vehicle is removed from service, the load is rescheduled, and repair is arranged.
3. Retain the repair record and confirm the repair before the vehicle returns to service.
4. If the vehicle is left unattended, record its location and security arrangements.

What this shows about pre-trip inspection:

• A hiss and an oil stain are exactly what a thorough walk-around is meant to catch. The fact they were found mid-run suggests either the defect developed after departure or the pre-trip check missed it. A proper pre-trip includes listening at each wheel-end, checking for oil/grease trails, and watching gauge behaviour.
• Drivers should check the gauge after a brake application, not just at idle, because a small leak may only show under demand.

Operator duties (chain of responsibility):

• Provide a vehicle that is roadworthy and maintain it to schedule.
• Have a defect-reporting and repair system that removes defective vehicles from service without pressuring drivers to continue.
• Ensure drivers are trained and have time to do proper pre-trip checks.
• Not penalise a driver for reporting a defect or missing a delivery window because of a safety stop.

The driver's decision to stop protects the driver, the operator, and the public; the operator's response determines whether the system works.