8.4 Handbook Brake Tests and Fault Decisions

Use a controlled stationary test area

Air-brake checks must be performed with the vehicle secured in a suitable location. Use the actual manufacturer’s procedure and your training, including wheel chocks and precautions when the parking brake must be released. Keep people out of the movement and crush zones. Do not disconnect lines or deliberately exhaust pressure on a public-road slope to demonstrate a test.

The handbook’s figures below are general checks, not a complete engineering inspection or universal settings for every component. If the vehicle procedure differs or the driver cannot carry out a step safely, obtain qualified guidance. Never use an imported test threshold from a different country’s licensing manual as Tasmania’s rule.

Hydraulic and vacuum-assisted brake checks

For hydraulic brakes, inspect lines, hoses, wheel backing plates, the master cylinder and reservoir for leaks, damage or chafing. Check the reservoir level using the specified fluid and procedure. Apply and hold the pedal: unusual sinking or a spongy feel can indicate leakage or air in the system. A pedal that continues sinking under sustained pressure needs assessment before use; adding fluid alone does not repair a leak.

For vacuum-assisted brakes, the handbook includes an engine-off retention check with full vacuum and expects low vacuum within 30 seconds and normal working vacuum within 60 seconds after starting. Use the manufacturer’s specified test, indications and safe securing procedure. At a suitable controlled location, check for pulling to one side under braking as trained. These checks apply to the hydraulic or vacuum system fitted; do not substitute air-reservoir pressures for them.

Tanks, circuits and pressure build-up

Where manual drain valves are fitted, the handbook calls for daily draining of tanks. Collect discharge appropriately rather than release contaminants onto the ground. Moisture and oil in the system can affect valves and other components. Automatic drainage and dryer systems have their own maintenance requirements; do not assume they eliminate every inspection.

The handbook’s circuit check includes draining one circuit and verifying that only its gauge empties. If both gauges empty, have the system checked before use. This is a check of separation, not permission to dismantle valves. Refill through the proper secured procedure.

At fast idle, the general build-up check is from zero to 80% of the manufacturer’s maximum pressure within five minutes. The maximum itself is vehicle-specific. A slow build can indicate a supply problem, leakage or another fault. Do not replace this with a universal 350-to-600 kPa test using separate rigid and combination times that the Tasmania handbook does not give.

Warning and leakage checks

The handbook describes the low-air warning at approximately 410 kPa in its general procedure. Confirm the actual vehicle’s specified warning point and function. A warning that does not operate, or operates unexpectedly, requires attention; knowing the gauge number is not enough if the alarm itself is faulty.

With the vehicle secured, the parking brake released as the procedure requires and the foot brake fully applied, observe the stated leakage check. The handbook allowance is 20 kPa per minute for a truck, plus 5 kPa for each trailer. Thus the general figure is 25 kPa/min for one trailer and 30 kPa/min for two. Follow the correct stabilisation and test conditions rather than compare an initial application drop to a timed leakage allowance.

After the stated application, the handbook calls for four further foot-brake applications and holding the fourth. There should not be more than half the pressure lost or a warning activated under that check. Interpret the whole sequence through the vehicle instructions; this does not establish a universal spring-brake 'pop-out' pressure.

Trailer breakaway and hauling-unit protection

The handbook procedure disconnects the appropriate trailer air lines under controlled stationary conditions, including opening self-sealing fittings as specified. The trailer brakes should apply automatically and remain applied for at least 15 minutes. Do not add an unsupported claim that this knowledge-test check must occur with a fully loaded trailer on a 12% gradient.

For the hauling-unit protection check, after escaping air settles the handbook requires pressure above 300 kPa, continued hauling-unit service-brake function and no unintended spring-brake application. That figure is a residual-pressure check in the described procedure. It is not a universal pressure at which all spring brakes engage.

Reconnect lines correctly, restore the protection control as required and recharge the system. Release and reapply the parking brake according to the procedure and walk around listening for leaks. Check all connections before removing chocks or moving. A system that fails the protection check must be repaired rather than driven with an improvised plugged line.

Interpret results responsibly

A general check can find a problem but cannot prove the entire brake system’s condition. Brake balance, adjustment, mechanical wear and other faults may need workshop inspection or testing equipment. Report failed or questionable results in writing with the test conditions and symptoms. Do not select a higher allowable number simply because the schedule is urgent.

For example, a truck with one trailer loses 30 kPa in one minute during the specified applied-leakage check. That exceeds the handbook’s 25 kPa/min reference. The driver should stop the departure process and obtain assessment. It is not made acceptable by treating the combination as if it had two trailers.

Key decisions

Test each function safely, use the correct vehicle procedure and act on failed results. Keep build-up, warning, leakage, reserve and breakaway figures attached to their distinct checks.

Official sources

Official handbook, general hydraulic and air brake checks, pages 53–56; NHVR Inspection Manual, brakes. Sources checked 10 October 2026.