Air Brake Systems Diagnosis Flashcards
7 cards from real 310T practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Air Brake Systems Diagnosis flashcards as text
A technician hears air leaking from the exhaust port of the brake application valve when brakes are fully released. This indicates:
Answer: A leaking primary or secondary inlet valve seat
A leaking inlet valve seat inside the brake valve allows pressurized reservoir air to pass through the valve and exhaust continuously when brakes are released.
The parking brake dash control valve pops out (applies) immediately after it is pushed in. What is the MOST likely cause?
Answer: System reservoir pressure is below hold-in threshold
The parking brake control valve requires minimum system pressure (typically 45 psi) to hold in; if pressure is too low, the valve cannot maintain its applied position.
During a brake balance test, the rear axle brakes grab harder than the front axle brakes. The FIRST area to inspect is:
Answer: Proportioning/limiting valve operation on the front circuit
A malfunctioning front-axle limiting or proportioning valve reduces delivered pressure to the front brakes, creating a front-to-rear imbalance.
A 30/30 combination spring brake chamber is being replaced. What is the CRITICAL safety step before disassembly?
Answer: Manually clamp or cage the spring before removing the chamber
The powerful coil spring inside a spring brake chamber must be mechanically caged before disassembly to prevent catastrophic release and injury.
What does it mean when the ABS warning lamp stays illuminated continuously after the vehicle exceeds 6 mph?
Answer: A fault code has been stored in the ABS ECU
A continuous ABS warning lamp above 6 mph indicates the ECU has detected a system fault and stored a diagnostic trouble code; the ABS function may be disabled.
Which test is used to verify the compressor governor cut-in and cut-out pressures?
Answer: Governor pressure test using a calibrated gauge at the wet tank
Installing a calibrated pressure gauge at the wet tank allows the technician to observe exact pressures at which the governor signals the compressor to load and unload.
A relay valve is delivering pressure to the rear brake chambers that is 20 psi higher than the signal pressure. This indicates:
Answer: A stuck open delivery valve causing constant full pressure delivery
A relay valve should deliver pressure equal to its signal input; delivery pressure significantly exceeding signal pressure indicates a stuck delivery valve allowing uncontrolled reservoir air flow.