Air Brakes Eng 1

Most heavy-duty vehicles nowadays have a dual air brake system. What is a dual air brake system?

Two air brake systems with separate sets of controls
Two air brake systems that share the same set of air tanks
A “primary” air brake system for everyday use and a “secondary” air brake system only for emergencies
Two separate air brake systems that use a single set of brake controls

How often should you drain your air tanks?

Once a week
At the end of each workday
Twice a week
Every two days.

What does the supply pressure gauge indicate?

The amount of pressure in the braking system
The amount of pressure in the air tanks
The amount of pressure the air tanks are intended to hold
The amount of pressure needed in the air tanks.

Which of the following statements about spring brakes are true?

They use air pressure to stop the vehicle.
Will not work if all air leaves the air brake system.
They are held by mechanical force.
They will arrive completely at 50 psi.

The main purpose of the alcohol evaporator is to:

Put alcohol in gas tanks
Remove alcohol from the compressor
Put alcohol in the air system
Put alcohol in the drain valves.

During the walkaround inspection, if a slack adjuster moves slightly more than an inch where the push rod attaches to it, then

It has the perfect amount of slack
It probably needs adjustment
The brakes will stop the vehicle very suddenly
Apply the brake pedal.

What are you testing when you wait for normal air pressure, release the parking brake, move the vehicle forward at about 5 mph, and apply the brakes firmly using the brake pedal?

The parking brakes
The service brakes
The emergency brakes
Brake accident

Some vehicles, such as buses, have a separate air tank used to do what?

Release the spring brakes.
Supply air to the braking system if the primary air tanks fail.
Convert the air brakes into an emergency braking system.
Enable the driver to disengage the parking brakes and continue driving normally.

The braking system that applies and releases the brakes when the driver uses the brake pedal is the ________________ brake system?

Emergency
Service
Parking
Trailer

How should you check that the service brakes are working properly?

Park on a level ground, wait for the pressure build up to normal, and release the parking brake, move the truck forward slowly 5 mph and apply the brake pedal as hard as you can
Park on a lightly steep surfacel, drain the air pressure, apply the parking brakes and check for movement
Park on a level ground, chock the wheels, put on the parking brake, when you have enough air pressure to do it, and shut the engine off
Stay tuned for signs

Let hot brakes cool before using the _______________ brakes.

Emergency
Parking
Hand
ABS brakes.

The air brake lag distance at 55 mph on dry pavement adds about how many feet?

32 feet the distance to stop
52 feet the distance to stop
72 feet the distance to stop
62 feet the distance to stop

What type of air do air brakes use?

Decompressed air
Warm air
Compressed air
Heated air

In a dual air brake system, which parts of braking does each system typically operate?

One system operates the brakes on the rear axle/axles and the trailer; the other operates the regular brakes on the front axle (and possibly a rear axle).
One system operates the brakes on the rear axle/axles; the other operates the regular brakes on the front axle and the trailer.
One system operates the brakes on the front and rear axles; the other operates the brakes on the trailer (and possibly a rear axle).
One system operates the brakes on the rear axle/axles; the other operates the regular brakes on the front axle (and possibly a rear axle), both supply air to the trailer.

If your truck or bus has dual parking control valves, you can use pressure from a separate tank to:

Balance the service brake system when you are parked
Release the spring emergency/parking brakes to move a short distance.
Brake harder if the main tank is getting low.
If the pressure drops too low the brakes will not work

Before driving a vehicle with a double air system, let the air compressor accumulate up to 100 psi of pressure in which of the following?

Only the primary system
The secondary system only
Both the primary and secondary systems.
You only have to increase the pressure to 60 psi in each system.

When braking on downgrades

Go slow enough so that a light, steady use of the brakes keeps you from speeding up.
Brake hard, then let up to cool brakes
Coast downhill, then apply the brakes hard
Apply normal brakes

Why are front brake limiting valves not present in newer trucks?

They were found to actually reduce the stopping power of a truck.
The braking systems of newer trucks are incompatible with front brake limiting valves.
Front brake limiting valves were not reliable and were sometimes responsible for brake failure.
They are, but they are just automatic.

A safety relief valve is installed in the first tank the air compressor pumps air to. The valve is usually set to open at what psi level?

130
140
150
170

Unnecessarily pressing and releasing the brake pedal can:

Change the air pressure of the brake
Accumulation of air pressure of the brake
let air go out and reduce the air pressure
Press and release the pedal

Trailers, semitrailers, and pole trailers with a gross weight of 4,500 pounds or less are exempt from?

Contract of carriage for loads
brake requirements
Bill of Lading (BOL)
Taxes

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