ASE T4 Air Brakes Diagnosis
and Repair Practice Exam
with 100 correct answers
RepairWhat is the typical cause of a rapid brake chamber stroke increase
when a brake application is made?
A. Faulty relay valve
B. Worn brake linings
C. Leaky brake chamber diaphragm
D. Air compressor governor malfunction
Answer B
When testing a tractor with a fully charged air system, the trailer brakes
do not release. What should be checked first?
A. Trailer relay valve
B. Tractor protection valve
C. Quick release valve
D. Anti-compounding valve
Answer B
RepairWhat is the MOST likely cause of a spring brake chamber not
releasing on a tandem axle truck?
A. A damaged service brake diaphragm
B. A clogged exhaust port in the spring brake modulating valve
C. An over-adjusted slack adjuster
D. A broken spring in the brake chamber
Answer B
RepairDuring a high-pressure test, the air pressure drops significantly
after the engine is turned off. The FIRST component to suspect would be
the:
A. Air compressor
B. Safety valve
C. One-way check valve
D. Pressure protection valve
Answer C
, A truck with air brakes has a pedal that feels spongy and goes to the floor
when applied. The most likely cause is:
A. Air in the hydraulic system
B. A defective quick release valve
C. An over-adjusted slack adjuster
D. Worn camshaft bushings
Answer A
ASE T4: Air Brakes Diagnosis and RepairThe air pressure gauge shows a
slower build-up of air pressure than normal. What could be the cause of
this condition?
A. Faulty air dryer
B. Leaking brake chambers
C. Malfunctioning unloader valve
D. A restricted air intake filter
Answer C.
Correct answer: C. Explanation: A malfunctioning unloader valve can lead
to slow air pressure build-up as it may not allow the compressor to switch
between the loaded and unloaded states efficiently.
ASE T4: Air Brakes Diagnosis and RepairIf the air brake system has a
significant delay in pressure drop after the engine is shut off, what is the
most likely problem?
A. Air dryer malfunction
B. A leak at the air compressor discharge line
C. Faulty air governor
D. Restricted air tank drain valve
Answer A
Correct answer: A. Explanation: A significant delay in the pressure drop
can indicate an air dryer malfunction, which may be failing to purge
properly, causing air to be trapped in the system.
When a service brake application feels uneven or jerky, what should be
suspected?
A. Contaminated brake linings
B. A faulty ABS modulator valve
C. A leaking diaphragm in the brake chamber
D. Unevenly adjusted slack adjusters
Answer D
If an automatic slack adjuster must be manually adjusted often, what is
the probable cause?
and Repair Practice Exam
with 100 correct answers
RepairWhat is the typical cause of a rapid brake chamber stroke increase
when a brake application is made?
A. Faulty relay valve
B. Worn brake linings
C. Leaky brake chamber diaphragm
D. Air compressor governor malfunction
Answer B
When testing a tractor with a fully charged air system, the trailer brakes
do not release. What should be checked first?
A. Trailer relay valve
B. Tractor protection valve
C. Quick release valve
D. Anti-compounding valve
Answer B
RepairWhat is the MOST likely cause of a spring brake chamber not
releasing on a tandem axle truck?
A. A damaged service brake diaphragm
B. A clogged exhaust port in the spring brake modulating valve
C. An over-adjusted slack adjuster
D. A broken spring in the brake chamber
Answer B
RepairDuring a high-pressure test, the air pressure drops significantly
after the engine is turned off. The FIRST component to suspect would be
the:
A. Air compressor
B. Safety valve
C. One-way check valve
D. Pressure protection valve
Answer C
, A truck with air brakes has a pedal that feels spongy and goes to the floor
when applied. The most likely cause is:
A. Air in the hydraulic system
B. A defective quick release valve
C. An over-adjusted slack adjuster
D. Worn camshaft bushings
Answer A
ASE T4: Air Brakes Diagnosis and RepairThe air pressure gauge shows a
slower build-up of air pressure than normal. What could be the cause of
this condition?
A. Faulty air dryer
B. Leaking brake chambers
C. Malfunctioning unloader valve
D. A restricted air intake filter
Answer C.
Correct answer: C. Explanation: A malfunctioning unloader valve can lead
to slow air pressure build-up as it may not allow the compressor to switch
between the loaded and unloaded states efficiently.
ASE T4: Air Brakes Diagnosis and RepairIf the air brake system has a
significant delay in pressure drop after the engine is shut off, what is the
most likely problem?
A. Air dryer malfunction
B. A leak at the air compressor discharge line
C. Faulty air governor
D. Restricted air tank drain valve
Answer A
Correct answer: A. Explanation: A significant delay in the pressure drop
can indicate an air dryer malfunction, which may be failing to purge
properly, causing air to be trapped in the system.
When a service brake application feels uneven or jerky, what should be
suspected?
A. Contaminated brake linings
B. A faulty ABS modulator valve
C. A leaking diaphragm in the brake chamber
D. Unevenly adjusted slack adjusters
Answer D
If an automatic slack adjuster must be manually adjusted often, what is
the probable cause?
