ASE S4 Brakes test questions
and answers
The air system is maintained at what pressure?
100 to 120 pounds per square inch.
At what pressure does the low pressure switch activate?
Below 60 pounds per square inch.
A safety or pop off valve is usually installed in which reservoir?
In the one closest to the compressor.
Why is the Wet tank referred to as such?
It is the one closest to the compressor and has the most water in it.
What is an after cooler used for in an air system?
It condenses and eliminates most of the water from an air system.
What does an air drier do in a air system?
They usually contain a bed of desiccant material which captures water and
oil.
What does the dual control foot valve control?
After the wet tank the valve controls the primary and secondary systems.
In a normal operation what does the primary air brake system control?
The rear axle brakes.
In a normal operation what does the secondary air brake system control?
The front axle brakes.
What does the two way check valve do in the air brake system?
It allows dominant pressure to activate the stoplight switch and to release
the parking brakes.
What is the standard releases of the parking brake system in the event of
a failure?
At least once during a failure of either primary or secondary system
pressure.
Why are relay valves used in a rear air brake system?
, To minimize delay of brake application on long wheel based applications.
What determines the crack pressures on a air brake system relay valve?
How heavily loaded the axle is. The size of the axle's brakes.
Aggressiveness of the linings.
What is a quick release valve used for in air brake systems?
It allows brake actuation air to be quickly exhausted near the brakes it
serves.
What is the minimum apply time of air brake systems?
0.45 seconds.
What is the minimum release time of air brake systems?
0.55 seconds.
What is a ratio valve in air brake systems?
Also known as a pressure reducing valve, limits air pressure to the front
axle. They have a variety of hold off pressures.
What is the first step in system diagnosis of air brake systems?
The driver should be interviewed.
If air brake systems are not applying and releasing properly, and grabbing
or dragging what could be the cause?
Defective supply system components.
If air brake systems have instability and premature wear what could be
the cause?
As little as a 4 pounds per square inch difference between axles can cause
this.
If all around braking performance is poor or low air pressure is prevalent
what could be the cause?
Clogged compressor air filter. Slipping belt. Air leaks. Restricted lines.
Defective governor. Malfunctioning air compressor.
If air system pressure is too high what could be the cause?
Defective governor. Reservoir safety valve. Governor's cut off pressure.
With the engine running at an idle what should be the pressure build up
time?
85 to 100 pounds per square inch within 45 seconds. 25 seconds at full
governed speed.
and answers
The air system is maintained at what pressure?
100 to 120 pounds per square inch.
At what pressure does the low pressure switch activate?
Below 60 pounds per square inch.
A safety or pop off valve is usually installed in which reservoir?
In the one closest to the compressor.
Why is the Wet tank referred to as such?
It is the one closest to the compressor and has the most water in it.
What is an after cooler used for in an air system?
It condenses and eliminates most of the water from an air system.
What does an air drier do in a air system?
They usually contain a bed of desiccant material which captures water and
oil.
What does the dual control foot valve control?
After the wet tank the valve controls the primary and secondary systems.
In a normal operation what does the primary air brake system control?
The rear axle brakes.
In a normal operation what does the secondary air brake system control?
The front axle brakes.
What does the two way check valve do in the air brake system?
It allows dominant pressure to activate the stoplight switch and to release
the parking brakes.
What is the standard releases of the parking brake system in the event of
a failure?
At least once during a failure of either primary or secondary system
pressure.
Why are relay valves used in a rear air brake system?
, To minimize delay of brake application on long wheel based applications.
What determines the crack pressures on a air brake system relay valve?
How heavily loaded the axle is. The size of the axle's brakes.
Aggressiveness of the linings.
What is a quick release valve used for in air brake systems?
It allows brake actuation air to be quickly exhausted near the brakes it
serves.
What is the minimum apply time of air brake systems?
0.45 seconds.
What is the minimum release time of air brake systems?
0.55 seconds.
What is a ratio valve in air brake systems?
Also known as a pressure reducing valve, limits air pressure to the front
axle. They have a variety of hold off pressures.
What is the first step in system diagnosis of air brake systems?
The driver should be interviewed.
If air brake systems are not applying and releasing properly, and grabbing
or dragging what could be the cause?
Defective supply system components.
If air brake systems have instability and premature wear what could be
the cause?
As little as a 4 pounds per square inch difference between axles can cause
this.
If all around braking performance is poor or low air pressure is prevalent
what could be the cause?
Clogged compressor air filter. Slipping belt. Air leaks. Restricted lines.
Defective governor. Malfunctioning air compressor.
If air system pressure is too high what could be the cause?
Defective governor. Reservoir safety valve. Governor's cut off pressure.
With the engine running at an idle what should be the pressure build up
time?
85 to 100 pounds per square inch within 45 seconds. 25 seconds at full
governed speed.
