ASE S4 Brakes
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.
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.
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.
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.
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.
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.
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.
