On a typical heavy-truck air brake system, what is the primary job of the air compressor governor?
Air Brakes
Question · Medium
Your heart has these. So do pipes.
Short
Typical air brake governor cut-out (compressor unload) pressure on a heavy truck is closest to which range?
Question · Easy
Common name for an air-brake reservoir; the service and supply ones together must hold at least 12 times the combined volume of the service brake chambers.
Air supply
Guess the Term
Chapter 1: Introduction & ASE T4 Certification Overview
1.1 ASE T4 Exam Specifications, Structure & Test-Taking Strategy
Study guide
The first (supply) reservoir downstream of the compressor on a heavy truck is commonly called the wet tank. Why is it called wet?
Read the clue and guess the term in 6 tries.
Game
An air dryer with a desiccant cartridge is installed on a tractor. What is its main purpose?
Kind of one-way valve that protects a service reservoir from losing pressure through a failure or leak on its supply side.
A technician finds excessive oil being expelled from the air dryer purge valve and oil contamination in the reservoirs. Which is the MOST likely root cause?
FMVSS 121 sets air system performance requirements for trucks. Which statement best reflects an FMVSS 121 air-buildup requirement?
Kind of dash instrument that shows service reservoir air pressure and must be accurate within plus or minus 7 percent of compressor cut-out.
1.2 Commercial Vehicle Brake Regulations, FMVSS 121 Standards & Safety
A heavy truck takes far too long to build air pressure from 85 to 100 psi during a buildup test. Technician A says a restricted air dryer or supply line could cause slow buildup. Technician B says worn compressor rings or a leaking discharge valve could cause it. Who is correct?
Swap tiles to line up three of the same term.
Term Match
At what reservoir pressure must the air brake low-pressure warning device activate, per common FMVSS 121 requirements?
Kind of document a carrier must keep for three months from the date it is prepared, listing defects that affect safe operation, including the service brakes.
What is the function of the safety (pressure relief) valve usually mounted on the supply (wet) reservoir?
A truck has a single-check valve between the supply reservoir and the primary reservoir. What does this check valve accomplish?
Flexible brake conduit, other than a vacuum tubing connector, that carries the fluid pressure or vacuum used to apply a vehicle's brakes.
Chapter 2: Air Supply System — Generation, Cleaning & Regulation
2.1 Air Compressors & Governors
Why are heavy-truck air systems divided into separate primary and secondary circuits?
Flip two cards at a time to find matching terms.
Term Pairs
The treadle (foot) valve on an air brake truck is best described as a:
Kind of valve on an air reservoir that is opened by hand to remove collected water and oil.
What is the primary purpose of a quick-release valve in an air brake system?
A relay valve is used at the rear axles of a long-wheelbase truck mainly to:
Kind of adjuster whose effective length must match on both ends of an axle.
Foundation brakes
2.2 Air Dryers & Moisture Management
A ratio (proportioning) valve on the front axle of some trucks is used to:
Question · Hard
Find five hidden terms in a grid of letters.
Term Search
On a tractor-trailer, the function of the tractor protection valve is to:
Kind of rotating brake surface that shoes press against; its thickness may not go below the maker's limit.
During an applied-leakage test on a straight truck (engine off, brakes fully applied), the maximum allowable pressure drop in one minute is generally about:
During a static air-leakage test (engine off, brakes released) on a single vehicle, the allowable leakage is generally about:
Kind of friction material whose minimum thickness at the shoe center is 4.8 mm on a steering axle with a continuous strip.
2.3 Reservoirs, Safety Valves & Leakage Testing
A technician hears a continuous air leak at the foot valve exhaust port only while the brakes are applied. The most likely cause is a:
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Two technicians discuss draining air reservoirs. Technician A says manual reservoir drain valves should be opened regularly to remove accumulated water and oil. Technician B says an automatic drain valve or air dryer can reduce, but does not always eliminate, the need to check for moisture. Who is correct?
Kind of brake part that carries friction material and is measured at its center for thickness on an air drum brake.
An air compressor is engine-driven and continuously turning. How does it stop building pressure when the system is fully charged?
A truck builds air normally but the governor never reaches cut-out, so the safety valve eventually opens. The MOST likely cause is:
Kind of friction element squeezed by a disc-brake caliper; on a steering-axle air disc it must be at least 3.2 mm.
Chapter 3: Air Brake Control Valves & Circuit Distribution
3.1 Dual Circuit Architecture & Treadle (Foot) Valves
What instrument and method best confirm actual reservoir cut-in and cut-out pressures?
A heavy truck's dash air gauge reads 90 psi but a calibrated master gauge teed into the same reservoir reads 120 psi. What is the correct conclusion?
Kind of brake chamber, required to match in size on both ends of an axle, that technicians cage to release the parking brake by hand.
Stationary braking
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