Michigan CDL - Air Brakes
Questions & Correct Answers
Why should you regularly drain the air tanks? - correct answer ✔✔Because compressed air
contains some water and the water collects in the tanks.
Compressed air usually contains a certain amount of moisture and compressor oil, which can
build up in the air storage tanks and damage the brake system. The tanks should be drained to
clean out these accumulations. On a tank with a manual drain valve, draining should be
performed at the end of each day of driving.
A low air pressure warning signal should activate: - correct answer ✔✔When tank pressure falls
below 60 psi.
In an air brake system, a low air pressure warning signal must come on if air pressure in the
tanks falls below 60 psi. This warning signal may come in the form of a light, a buzzer, or a wig
wag.
Vehicles equipped with Anti-Lock Braking Systems (ABS) have ____ malfunction lamps to
indicate when the ABS is not working. - correct answer ✔✔Yellow
Vehicles with ABS have yellow malfunction lamps to alert drivers when the braking systems are
not working. Be sure you know where the malfunction lamp on your vehicle is before beginning
a trip.
A dual air brake system: - correct answer ✔✔Consists of two separate air brake systems that
share a single set of controls.
, A dual air brake system is made up of two separate air brake systems. The systems share a single
set of brake controls, but each has its own air tanks, hoses, and lines. One system typically
operates the regular brakes on the rear axle or axles while the other system operates the
regular brakes on the front axle.
A safety valve is set to open at ____ pounds per square inch (psi). - correct answer ✔✔150
The safety valve protects air tanks and the rest of an air brake system from accumulating too
much air pressure. The safety valve is usually set to open at 150 psi.
Air pressure should build up in a single air system within: - correct answer ✔✔Three minutes.
In single air systems, air pressure should build from approximately 50 to 90 psi within three
minutes.
Some air brake systems use alcohol: - correct answer ✔✔To reduce the risk of ice forming in air
brake valves.
Some air brake systems contain an alcohol evaporator. This device introduces alcohol into the
braking system to inhibit the formation of ice.
Spring brakes come on: - correct answer ✔✔When too much air pressure is lost.
Spring brakes come on automatically when air pressure drops to an unsafe psi level. Instead of
waiting for the spring brakes to automatically activate, you should safely exit the road as soon as
you notice the low pressure warning signal and bring your vehicle to a stop while you are still
able to control the brakes.
On trucks and buses, where are ABS malfunction lamps located? - correct answer ✔✔On the
instrument panel
Questions & Correct Answers
Why should you regularly drain the air tanks? - correct answer ✔✔Because compressed air
contains some water and the water collects in the tanks.
Compressed air usually contains a certain amount of moisture and compressor oil, which can
build up in the air storage tanks and damage the brake system. The tanks should be drained to
clean out these accumulations. On a tank with a manual drain valve, draining should be
performed at the end of each day of driving.
A low air pressure warning signal should activate: - correct answer ✔✔When tank pressure falls
below 60 psi.
In an air brake system, a low air pressure warning signal must come on if air pressure in the
tanks falls below 60 psi. This warning signal may come in the form of a light, a buzzer, or a wig
wag.
Vehicles equipped with Anti-Lock Braking Systems (ABS) have ____ malfunction lamps to
indicate when the ABS is not working. - correct answer ✔✔Yellow
Vehicles with ABS have yellow malfunction lamps to alert drivers when the braking systems are
not working. Be sure you know where the malfunction lamp on your vehicle is before beginning
a trip.
A dual air brake system: - correct answer ✔✔Consists of two separate air brake systems that
share a single set of controls.
, A dual air brake system is made up of two separate air brake systems. The systems share a single
set of brake controls, but each has its own air tanks, hoses, and lines. One system typically
operates the regular brakes on the rear axle or axles while the other system operates the
regular brakes on the front axle.
A safety valve is set to open at ____ pounds per square inch (psi). - correct answer ✔✔150
The safety valve protects air tanks and the rest of an air brake system from accumulating too
much air pressure. The safety valve is usually set to open at 150 psi.
Air pressure should build up in a single air system within: - correct answer ✔✔Three minutes.
In single air systems, air pressure should build from approximately 50 to 90 psi within three
minutes.
Some air brake systems use alcohol: - correct answer ✔✔To reduce the risk of ice forming in air
brake valves.
Some air brake systems contain an alcohol evaporator. This device introduces alcohol into the
braking system to inhibit the formation of ice.
Spring brakes come on: - correct answer ✔✔When too much air pressure is lost.
Spring brakes come on automatically when air pressure drops to an unsafe psi level. Instead of
waiting for the spring brakes to automatically activate, you should safely exit the road as soon as
you notice the low pressure warning signal and bring your vehicle to a stop while you are still
able to control the brakes.
On trucks and buses, where are ABS malfunction lamps located? - correct answer ✔✔On the
instrument panel
