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
The secondary reservoir pressure is normal, but primary reservoir pressure will not build above 70 psi. The MOST likely cause is:
Answer: A restricted primary reservoir check valve
A restricted check valve between the wet tank and primary reservoir limits air flow, preventing the primary circuit from reaching full system pressure.
During a trailer service brake application, air exhausts from the trailer supply gladhand instead of the service gladhand. This indicates:
Answer: Reversed gladhand connections at the trailer nose
Reversed gladhand connections cause service air to flow into the supply line, which vents through the emergency portion of the trailer control valve.
A technician finds water and rust in the primary reservoir but not the secondary. What is the MOST likely cause?
Answer: The primary reservoir check valve is leaking, bypassing the air dryer
A leaking primary reservoir check valve can allow unfiltered, unprocessed air to bypass the dryer and enter the primary reservoir directly.
What is the purpose of the double-check valve in an air brake system?
Answer: To supply the highest pressure source from either the primary or secondary circuit to a single output
A double-check valve selects and passes the higher of two input pressures to a single output, commonly used to ensure either circuit can operate the spring brake control valve.
A Class 8 truck repeatedly trips the low air pressure warning at 60 psi within minutes of starting the engine. What should be checked FIRST?
Answer: Compressor belt tension and condition
A slipping or broken compressor drive belt prevents the compressor from building pressure, causing system pressure to remain low and triggering the warning buzzer.
When diagnosing a foundation brake that runs hot on one axle end only, the technician should inspect the:
Answer: Automatic slack adjuster for proper operation and free movement
A seized or improperly adjusted automatic slack adjuster keeps the brake partially applied, generating excessive heat at that wheel end.
On a tractor-trailer combination, maximum pressure drop during a combined leakage test with brakes applied must not exceed:
Answer: 6 psi per minute
FMCSA regulations allow up to 6 psi per minute pressure drop for combination vehicles during a static leakage test with service brakes applied.