ASE S4 Brakes |Complete Questions with Graded
A+ Correct 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.
If air system pressure build up time takes too long what could be the cause?
Leaks. Dirty air filter.
When draining the air tank you find excessive oil what could be the cause?
Blocked air filter. If air filter not blocked then suspect worn compressor rings. Air drier ejection valve.
How often should self lubricated air compressor oil level checked?
Daily.
Before diagnosing the air system shut off the engine and then do what?
Block the wheels to prevent vehicle movement.
A+ Correct 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.
If air system pressure build up time takes too long what could be the cause?
Leaks. Dirty air filter.
When draining the air tank you find excessive oil what could be the cause?
Blocked air filter. If air filter not blocked then suspect worn compressor rings. Air drier ejection valve.
How often should self lubricated air compressor oil level checked?
Daily.
Before diagnosing the air system shut off the engine and then do what?
Block the wheels to prevent vehicle movement.
