Arkansas CDL — Air Brakes: Safe Driving Practices Practice Test

Question 1

The manual names two ways an air compressor may be kept cool. Which pair is correct?

Accepted Answer

Cooling by air, or cooling through the engine's cooling system — A compressor may be air cooled, or it may share the engine's cooling system. Neither the alcohol evaporator nor the tank drains has anything to do with cooling it.

Answer

Cooling by alcohol from the evaporator, or by water drained from the tanks

Answer

Cooling by the brake drums, or by the slack adjusters

Answer

Cooling by the safety valve venting air, or by the governor shutting it off

Question 2

What is the job of the air compressor governor?

Accepted Answer

It controls when the compressor pumps air into the storage tanks — The governor decides when the compressor pumps: it stops pumping at the cut-out level, around 125 psi, and starts it again at the cut-in level, around 100 psi. Releasing excess pressure is the safety valve's job.

Answer

It limits how fast the truck can go on air brakes

Answer

It releases air if tank pressure gets too high

Answer

It warns you when air pressure is low

Question 3

On an air-braked vehicle with drum brakes, how are the wheels and brake drums arranged?

Accepted Answer

The drums are at each end of the axles, and the wheels are bolted to them — Each axle end carries a brake drum, and the wheel is bolted onto it. The braking parts sit inside the drum, where the shoes and linings press outward to create friction.

Answer

The drums sit in the cab and connect to the wheels by cables

Answer

Each drum is mounted on the driveshaft, away from the wheels

Answer

Only the front axle has drums; the rear wheels rely on the spring brakes alone

Question 4

Where is the safety relief valve installed in an air brake system?

Accepted Answer

In the first tank that the compressor pumps air into — The safety relief valve sits in the first tank fed by the compressor. It guards that tank, and everything downstream of it, against excess pressure.

Answer

On each brake chamber at the wheels

Answer

On the dash, next to the parking brake knob

Answer

On the last tank before the trailer air lines

Question 5

Besides hiding the real fault, why does the manual call it dangerous to hand-adjust an automatic slack adjuster?

Accepted Answer

It can give you a false sense of security about how well the brakes work — Bringing the pushrod stroke back within limits by hand usually covers up a mechanical problem without fixing it, and it may leave you trusting the brakes more than you should. The brake is likely to drift out of adjustment again soon.

Answer

It cancels your CDL air brake endorsement

Answer

It disconnects the ABS

Answer

It makes the compressor run nonstop

Question 6

On a tractor, truck, or bus with ABS, where is the yellow ABS malfunction lamp?

Accepted Answer

On the instrument panel — Tractors, trucks, and buses show their yellow ABS warning lamp on the instrument panel. Trailers are different: their lamps are mounted on the left side, at the front or rear corner.

Answer

On the left rear corner of the frame

Answer

Under the hood, next to the compressor

Answer

On the right side mirror

Question 7

In a wedge brake, what does the brake chamber push rod do?

Accepted Answer

Drives a wedge between the ends of two brake shoes, spreading them against the drum — With wedge brakes, the push rod forces a wedge straight in between the two shoe ends. That spreads the shoes apart and forces them outward onto the inner surface of the drum.

Answer

Turns a power screw that clamps a rotor

Answer

Twists an s-shaped camshaft

Answer

Pulls the shoes away from the drum to let the wheel roll

Question 8

Your truck has automatic slack adjusters. Do you still need to check them during your inspection?

Accepted Answer

Yes; they self-adjust when the brakes are fully applied, but they still have to be checked — Automatic slack adjusters take up slack during full brake applications, but the manual says to check them anyway. A brake found out of adjustment points to a problem that belongs at a repair shop.

Answer

No; automatic adjusters never go out of adjustment

Answer

Only after the truck passes 100,000 miles

Answer

Only if the ABS lamp stays on

Question 9

During the final air brake check, your governor fails to cut the compressor in and out as it should. Why does that matter?

Accepted Answer

It may fail to hold enough air pressure to drive safely — If the governor does not cut in and out as described, it may need repair. A malfunctioning governor may let air pressure fall short of what safe driving needs.

Answer

It only affects how loud the compressor runs

Answer

It causes the ABS lamp to stay on

Answer

It makes the safety valve open at 55 psi

Question 10

When does an antilock braking system actually step in?

Accepted Answer

Only when the wheels are about to lock up — ABS is added on top of your normal brakes and acts only when wheels are close to locking. It does not raise or lower your normal braking capability.

Answer

Every time you press the brake pedal

Answer

Only at speeds above 55 mph

Answer

Only when the low air warning is on

Question 11

Since what year have all vehicles been built with automatic slack adjusters?

Accepted Answer

1994 — The manual states that every vehicle built since 1994 has automatic slack adjusters. They still need to be checked.

Answer

1975

Answer

1997

Answer

2005

Question 12

Some automatic air tank drains come fitted with electric heating devices. What are the heaters for?

Accepted Answer

Keeping the automatic drain from freezing in cold weather — Automatic drains push out water and oil by themselves, but the drain can freeze when it is cold. Electric heaters on some automatic tanks help keep that from happening.

Answer

Warming the brake linings so they grip better

Answer

Drying the air before it reaches the compressor

Answer

Raising tank pressure faster after start-up

Arkansas CDL — Air Brakes: Safe Driving Practices practice test

Study questions with answers

1. The manual names two ways an air compressor may be kept cool. Which pair is correct?

2. What is the job of the air compressor governor?

3. On an air-braked vehicle with drum brakes, how are the wheels and brake drums arranged?

4. Where is the safety relief valve installed in an air brake system?

5. Besides hiding the real fault, why does the manual call it dangerous to hand-adjust an automatic slack adjuster?

6. On a tractor, truck, or bus with ABS, where is the yellow ABS malfunction lamp?

7. In a wedge brake, what does the brake chamber push rod do?

8. Your truck has automatic slack adjusters. Do you still need to check them during your inspection?

9. During the final air brake check, your governor fails to cut the compressor in and out as it should. Why does that matter?

10. When does an antilock braking system actually step in?

11. Since what year have all vehicles been built with automatic slack adjusters?

12. Some automatic air tank drains come fitted with electric heating devices. What are the heaters for?

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