Which inspection procedure should you use on a vehicle with air brakes?

The basic seven-step inspection procedure, with extra air brake checks

A separate three-step air brake procedure

Only a walk-around of the air tanks

During the engine compartment check, what do you check on a belt-driven air compressor?

The condition and tightness of the belt

Before checking the slack adjusters on s-cam brakes, how should you prepare the vehicle?

Park on level ground, chock the wheels, and release the parking brakes

Park on a slope with the parking brakes on

Leave the engine running in gear

How do you check a slack adjuster by hand?

Wear gloves and pull hard on each slack adjuster you can reach

Turn its adjusting nut until it stops

Do automatic slack adjusters need to be checked?

Yes, they must be checked even though they adjust themselves

No, they never go out of adjustment

A brake with an automatic adjuster has a pushrod stroke past the legal limit. What does that indicate?

A mechanical problem in the adjuster, the brake parts, or the installation

Normal wear that needs no attention

That the air tanks need draining

What is recommended when brakes with automatic adjusters are found out of adjustment?

Take the vehicle to a repair facility as soon as possible

Adjust them by hand and keep driving as usual

Ignore it until the next yearly inspection

Why is manually adjusting an automatic slack adjuster dangerous?

It may give a false sense of security about the brakes

It always breaks the adjuster at once

It drains all air from the system

When should an automatic adjuster be adjusted by hand?

Only as a temporary measure in an emergency

How long may a crack in a brake drum be?

No longer than one half the width of the friction area

No longer than the full width of the friction area

What must brake linings not be?

Loose or soaked with oil or grease

What do you check on the air hoses connected to the brake chambers?

That they are not cut or worn from rubbing

That they are painted red and blue

How do you check the governor cut-in pressure?

With the engine idling, step on and off the brake to lower tank pressure

Shut off the engine and open a drain valve

Pull the parking brake knob in and out

Why must a governor that does not cut in and out properly be fixed?

It may not keep enough air pressure for safe driving

For the air leakage test with brakes released, how do you set up?

Fully charge the system, turn off the engine, and release the parking brake

Run the engine at a fast idle with the brakes on

Drain one tank and leave the engine running

Your air loss rate is too high. What should you do?

Check for air leaks and fix them before driving

Drive slowly to the next terminal

Pump the brakes to raise the pressure

How do you test the low pressure warning signal?

Engine off, electrical power on, step on and off the brake pedal

Engine at fast idle, pull the parking brake

Engine off, open the tank drains fully

In a dual air system, which tank do you watch in the low pressure warning test?

The tank with the lowest air pressure

The tank with the highest air pressure

In the spring brake check, at what pressure should the parking brake valve pop out?

At the manufacturer’s specification, 20 – 45 psi

On a tractor-trailer, which valves should pop out when pressure falls during the spring brake check?

The tractor protection valve and parking brake valve

The safety valve and drain valve

If the vehicle has larger than minimum air tanks, can the buildup time be longer?

Yes, it can be longer and still be safe

No, it must always be 45 seconds or less

No, larger tanks must fill faster

In single air systems (pre-1975), what is the typical buildup requirement?

85 to 100 psi within 45 seconds

Air pressure does not build up fast enough. What should you do?

Do not drive until the problem is fixed

Drive until the warning light comes on

How do you test the parking brake?

Put it on and gently pull against it in a low gear

Push the brake pedal hard with it on

What should you note during the service brake test?

Pulling to one side, unusual feel, or delayed stopping

In a normal stop with a manual transmission, when should you push the clutch in?

When the engine rpm is down close to idle

How does ABS help when it senses impending lockup?

It reduces the braking pressure to a safe level

Does having ABS on only the tractor or only one axle still help?

Yes, it still gives you more control during braking

No, ABS must be on every axle to work

No, it makes jackknifing more likely

When only the tractor has ABS and the trailer begins to swing out, what should you do?

Let up on the brakes if you can safely do so

Turn sharply toward the trailer

How should you brake a tractor-trailer combination that has ABS?

As you always have, with only the force needed to stop safely

When may you fully apply the brakes in an emergency stop?

When you always drive a vehicle with working ABS on all axles

Your ABS malfunctions. What should you do?

Drive normally, but get the system serviced soon

Inspecting and using air brakes

Practice this topic79 questions

Questions and answers

Which inspection procedure should you use on a vehicle with air brakes?

The basic seven-step inspection procedure, with extra air brake checks

Use the seven-step method from Section 2 and add the air brake items where they fit.
Section 5 · 5.3 – Inspecting Air Brake Systems ↗PDF, 41 MB
During the engine compartment check, what do you check on a belt-driven air compressor?

The condition and tightness of the belt

A belt-driven compressor needs a drive belt in good condition and properly tight.
Section 5 · 5.3.1 – During Step 2 Engine Compartment Checks ↗PDF, 41 MB
Before checking the slack adjusters on s-cam brakes, how should you prepare the vehicle?

Park on level ground, chock the wheels, and release the parking brakes

The parking brakes must be off so the slack adjusters can move, so chock the wheels on level ground.
Section 5 · 5.3.2 – During Step 5 Walk-around Inspection ↗PDF, 41 MB
How do you check a slack adjuster by hand?

Wear gloves and pull hard on each slack adjuster you can reach

Pull hard on every slack adjuster within reach, wearing gloves.
Section 5 · 5.3.2 – During Step 5 Walk-around Inspection ↗PDF, 41 MB
How much may a slack adjuster move where the push rod attaches before it probably needs adjustment?

About one inch

Movement of more than about one inch means the brake probably needs adjustment.
Section 5 · 5.3.2 – During Step 5 Walk-around Inspection ↗PDF, 41 MB
What is the most common problem found in roadside inspections?

Out-of-adjustment brakes

Brakes out of adjustment are found more than any other problem at roadside inspections.
Section 5 · 5.3.2 – During Step 5 Walk-around Inspection ↗PDF, 41 MB
Since what year have all vehicles been built with automatic slack adjusters?

1994

All vehicles built since 1994 have automatic slack adjusters, and they must still be checked.
Section 5 · 5.3.2 – During Step 5 Walk-around Inspection ↗PDF, 41 MB
Do automatic slack adjusters need to be checked?

Yes, they must be checked even though they adjust themselves

They adjust during full brake applications, but you must still check them.
Section 5 · 5.3.2 – During Step 5 Walk-around Inspection ↗PDF, 41 MB
A brake with an automatic adjuster has a pushrod stroke past the legal limit. What does that indicate?

A mechanical problem in the adjuster, the brake parts, or the installation

Too much stroke on an automatic adjuster points to a mechanical problem or bad installation.
Section 5 · 5.3.2 – During Step 5 Walk-around Inspection ↗PDF, 41 MB
What is recommended when brakes with automatic adjusters are found out of adjustment?

Take the vehicle to a repair facility as soon as possible

Manual adjustment usually hides the real problem, so get the vehicle repaired as soon as you can.
Section 5 · 5.3.2 – During Step 5 Walk-around Inspection ↗PDF, 41 MB
Why is manually adjusting an automatic slack adjuster dangerous?

It may give a false sense of security about the brakes

Manual adjustment masks the problem, so the driver may think the brakes are fine when they are not.
Section 5 · 5.3.2 – During Step 5 Walk-around Inspection ↗PDF, 41 MB
When should an automatic adjuster be adjusted by hand?

Only as a temporary measure in an emergency

Manual adjustment is only a temporary emergency fix, because the brake will soon be out of adjustment again.
Section 5 · 5.3.2 – During Step 5 Walk-around Inspection ↗PDF, 41 MB
How long may a crack in a brake drum be?

No longer than one half the width of the friction area

Drums or discs must not have cracks longer than half the width of the friction area.
Section 5 · 5.3.2 – During Step 5 Walk-around Inspection ↗PDF, 41 MB
What must brake linings not be?

Loose or soaked with oil or grease

Linings must not be loose, soaked with oil or grease, or dangerously thin.
Section 5 · 5.3.2 – During Step 5 Walk-around Inspection ↗PDF, 41 MB
What do you check on the air hoses connected to the brake chambers?

That they are not cut or worn from rubbing

Brake chamber hoses must not be cut or worn from rubbing.
Section 5 · 5.3.2 – During Step 5 Walk-around Inspection ↗PDF, 41 MB
In the final air brake check, at about what pressure should the compressor start pumping?

About 100 psi

Pumping should start at about 100 psi and stop at about 125 psi, per the manufacturer.
Section 5 · 5.3.3 – Step 7 Final Air Brake Check ↗PDF, 41 MB
In the final air brake check, at about what pressure should the compressor stop pumping?

About 125 psi

The governor should cut out the compressor at about 125 psi.
Section 5 · 5.3.3 – Step 7 Final Air Brake Check ↗PDF, 41 MB
At what engine speed do you check the governor cut-out pressure?

A fast idle

Run the engine at a fast idle and watch for the gauge to stop rising at the cut-out pressure.
Section 5 · 5.3.3 – Step 7 Final Air Brake Check ↗PDF, 41 MB
How do you check the governor cut-in pressure?

With the engine idling, step on and off the brake to lower tank pressure

Fanning the brake lowers pressure until the compressor cuts in and pressure starts to rise.
Section 5 · 5.3.3 – Step 7 Final Air Brake Check ↗PDF, 41 MB
Why must a governor that does not cut in and out properly be fixed?

It may not keep enough air pressure for safe driving

A faulty governor may not keep enough air for safe driving.
Section 5 · 5.3.3 – Step 7 Final Air Brake Check ↗PDF, 41 MB
For the air leakage test with brakes released, how do you set up?

Fully charge the system, turn off the engine, and release the parking brake

With a fully charged system, typically 125 psi, shut off the engine, push in the parking brake, and time the drop.
Section 5 · 5.3.3 – Step 7 Final Air Brake Check ↗PDF, 41 MB
With the brakes released, what is the most air pressure a single vehicle may lose in one minute?

Less than two psi

The loss rate should be under two psi in one minute for single vehicles.
Section 5 · 5.3.3 – Step 7 Final Air Brake Check ↗PDF, 41 MB
With the brakes released, what is the most air pressure a combination vehicle may lose in one minute?

Less than three psi

The loss rate should be under three psi in one minute for combination vehicles.
Section 5 · 5.3.3 – Step 7 Final Air Brake Check ↗PDF, 41 MB
For the applied leakage test, how long do you hold the foot brake fully applied?

One minute

With the engine off and parking brake released, hold the foot brake for one minute and watch the gauge.
Section 5 · 5.3.3 – Step 7 Final Air Brake Check ↗PDF, 41 MB
With the foot brake fully applied, how much pressure loss in one minute is too much for a single vehicle?

More than three psi

For a single vehicle, a drop of more than three psi in one minute is too much.
Section 5 · 5.3.3 – Step 7 Final Air Brake Check ↗PDF, 41 MB
With the foot brake fully applied, how much pressure loss in one minute is too much for a combination vehicle?

More than four psi

For a combination vehicle, more than four psi in one minute is too much.
Section 5 · 5.3.3 – Step 7 Final Air Brake Check ↗PDF, 41 MB
In the applied leakage test, what is the governor cutoff pressure range given?

120 – 140 psi

You build air to governor cutoff, 120 to 140 psi, before shutting off the engine for this test.
Section 5 · 5.3.3 – Step 7 Final Air Brake Check ↗PDF, 41 MB
Your air loss rate is too high. What should you do?

Check for air leaks and fix them before driving

Too much air loss could make you lose your brakes while driving, so fix leaks first.
Section 5 · 5.3.3 – Step 7 Final Air Brake Check ↗PDF, 41 MB
How do you test the low pressure warning signal?

Engine off, electrical power on, step on and off the brake pedal

With enough air to clear the warning, shut the engine off, turn power on, and fan the pedal to lower pressure.
Section 5 · 5.3.3 – Step 7 Final Air Brake Check ↗PDF, 41 MB
During the warning signal test, before the tank pressure drops to less than what must the warning come on?

55 psi

The warning must come on before pressure in the tank falls below 55 psi.
Section 5 · 5.3.3 – Step 7 Final Air Brake Check ↗PDF, 41 MB
In a dual air system, which tank do you watch in the low pressure warning test?

The tank with the lowest air pressure

In dual systems the warning must come on before the lowest tank falls below 55 psi.
Section 5 · 5.3.3 – Step 7 Final Air Brake Check ↗PDF, 41 MB
If the low pressure warning does not work in a single-circuit air system, what could happen?

Sudden emergency braking

You could lose air without knowing it, which could cause sudden emergency braking.
Section 5 · 5.3.3 – Step 7 Final Air Brake Check ↗PDF, 41 MB
In the spring brake check, at what pressure should the parking brake valve pop out?

At the manufacturer’s specification, 20 – 45 psi

Keep fanning off air, and the valve should close at 20 to 45 psi, which puts on the spring brakes.
Section 5 · 5.3.3 – Step 7 Final Air Brake Check ↗PDF, 41 MB
On a tractor-trailer, which valves should pop out when pressure falls during the spring brake check?

The tractor protection valve and parking brake valve

On a tractor-trailer both the tractor protection valve and parking brake valve should close.
Section 5 · 5.3.3 – Step 7 Final Air Brake Check ↗PDF, 41 MB
In a dual air system at operating rpms, how fast should pressure build from 85 to 100 psi?

Within 45 seconds

Dual systems should build from 85 to 100 psi within 45 seconds.
Section 5 · 5.3.3 – Step 7 Final Air Brake Check ↗PDF, 41 MB
If the vehicle has larger than minimum air tanks, can the buildup time be longer?

Yes, it can be longer and still be safe

Larger tanks take longer to fill, so check the manufacturer’s specifications.
Section 5 · 5.3.3 – Step 7 Final Air Brake Check ↗PDF, 41 MB
In single air systems (pre-1975), what is the typical buildup requirement?

50 to 90 psi within 3 minutes

Older single systems typically build from 50 to 90 psi within 3 minutes.
Section 5 · 5.3.3 – Step 7 Final Air Brake Check ↗PDF, 41 MB
At what engine speed is the single air system buildup test done?

An idle speed of 600-900 rpms

The pre-1975 single system test is at an idle of 600-900 rpm.
Section 5 · 5.3.3 – Step 7 Final Air Brake Check ↗PDF, 41 MB
Air pressure does not build up fast enough. What should you do?

Do not drive until the problem is fixed

Slow buildup can let pressure drop too low on the road and force an emergency stop.
Section 5 · 5.3.3 – Step 7 Final Air Brake Check ↗PDF, 41 MB
How do you test the parking brake?

Put it on and gently pull against it in a low gear

Stop, set the parking brake, and pull gently against it in a low gear to see it holds.
Section 5 · 5.3.3 – Step 7 Final Air Brake Check ↗PDF, 41 MB
At about what speed do you test the service brakes?

About five mph

Move forward slowly at about five mph and apply the brakes firmly.
Section 5 · 5.3.3 – Step 7 Final Air Brake Check ↗PDF, 41 MB
What should you note during the service brake test?

Pulling to one side, unusual feel, or delayed stopping

The test can reveal problems you would otherwise find only when you need the brakes.
Section 5 · 5.3.3 – Step 7 Final Air Brake Check ↗PDF, 41 MB
In a normal stop with a manual transmission, when should you push the clutch in?

When the engine rpm is down close to idle

Wait until rpm is near idle before pushing in the clutch, then select a starting gear.
Section 5 · 5.4.1 – Normal Stops ↗PDF, 41 MB
Without ABS, what happens when your steering wheels lock up?

You lose steering control

Locked steering wheels mean no steering, and locked other wheels can cause skids or jackknifes.
Section 5 · 5.4.2 – Braking with Antilock Brakes ↗PDF, 41 MB
How does ABS help when it senses impending lockup?

It reduces the braking pressure to a safe level

The computer cuts braking pressure to a safe level so you keep control.
Section 5 · 5.4.2 – Braking with Antilock Brakes ↗PDF, 41 MB
Does having ABS on only the tractor or only one axle still help?

Yes, it still gives you more control during braking

Even partial ABS gives more control over the vehicle while braking.
Section 5 · 5.4.2 – Braking with Antilock Brakes ↗PDF, 41 MB
When only the tractor has ABS and the trailer begins to swing out, what should you do?

Let up on the brakes if you can safely do so

Watch the trailer and ease off the brakes, if safe, when it starts to swing out.
Section 5 · 5.4.2 – Braking with Antilock Brakes ↗PDF, 41 MB
When only the trailer has ABS, what is less likely?

The trailer swinging out

Trailer ABS makes trailer swing less likely, but ease off if you start a tractor jackknife.
Section 5 · 5.4.2 – Braking with Antilock Brakes ↗PDF, 41 MB
How should you brake a tractor-trailer combination that has ABS?

As you always have, with only the force needed to stop safely

Brake the same way whether ABS is on the tractor, trailer, or both.
Section 5 · 5.4.2 – Braking with Antilock Brakes ↗PDF, 41 MB
When may you fully apply the brakes in an emergency stop?

When you always drive a vehicle with working ABS on all axles

The only exception is a straight truck or combination with working ABS on all axles.
Section 5 · 5.4.2 – Braking with Antilock Brakes ↗PDF, 41 MB
Your ABS malfunctions. What should you do?

Drive normally, but get the system serviced soon

You still have regular brakes, so drive normally and have the ABS fixed soon.
Section 5 · 5.4.2 – Braking with Antilock Brakes ↗PDF, 41 MB
How do you use the controlled braking method?

Brake as hard as you can without locking the wheels

Apply the brakes hard without locking the wheels, and keep steering movements very small.
Section 5 · 5.4.3 – Emergency Stops ↗PDF, 41 MB
In controlled braking, what should you do if the wheels lock?

Release the brakes, then re-apply as soon as you can

Release the brakes if the wheels lock or you need a larger steering correction, then brake again.
Section 5 · 5.4.3 – Emergency Stops ↗PDF, 41 MB
In stab braking, when do you release the brakes?

When the wheels lock up

Apply the brakes all the way, release when the wheels lock, and apply fully again once they roll.
Section 5 · 5.4.3 – Emergency Stops ↗PDF, 41 MB
In stab braking, how long can it take for the wheels to start rolling after you release the brakes?

Up to one second

Wait for the wheels to roll, which can take up to one second, or the vehicle will not straighten out.
Section 5 · 5.4.3 – Emergency Stops ↗PDF, 41 MB
What is brake lag?

The time required for the brakes to work after the pedal is pushed

Air brakes add a delay while air flows through the lines to the brakes.
Section 5 · 5.4.4 – Stopping Distance ↗PDF, 41 MB
How long does it take air to flow through the lines to the brakes?

One half second or more

Hydraulic brakes work instantly, but air brakes take one half second or more.
Section 5 · 5.4.4 – Stopping Distance ↗PDF, 41 MB
Which four factors make up total stopping distance for vehicles with air brakes?

Perception, reaction, brake lag, and braking distance

Air brakes add brake lag distance to perception, reaction, and braking distance.
Section 5 · 5.4.4 – Stopping Distance ↗PDF, 41 MB
At 55 mph on dry pavement, how much distance does air brake lag add?

About 32 feet

Brake lag at 55 mph on dry pavement adds about 32 feet.
Section 5 · 5.4.4 – Stopping Distance ↗PDF, 41 MB
At 55 mph with good traction and brakes, what is the total stopping distance with air brakes for an average driver?

Over 450 feet

Adding brake lag brings the total stopping distance at 55 mph to over 450 feet.
Section 5 · 5.4.4 – Stopping Distance ↗PDF, 41 MB
What leads to brake fade?

Excessive use of the service brakes, causing overheating

Overusing the service brakes instead of engine braking overheats them and causes fade.
Section 5 · 5.4.5 – Brake Fading or Failure ↗PDF, 41 MB
What happens to brake drums when they overheat?

They expand, so shoes must move farther and contact force drops

Expanded drums make the shoes travel farther, reducing braking force.
Section 5 · 5.4.5 – Brake Fading or Failure ↗PDF, 41 MB
Why can brakes out of adjustment lead to fade on the other brakes?

They stop doing their share, so the others overheat

Every brake must do its share. When some quit, the rest overheat and fade.
Section 5 · 5.4.5 – Brake Fading or Failure ↗PDF, 41 MB
When can brakes get out of adjustment quickly?

Especially when they are hot

Brakes can go out of adjustment fast, especially when hot, so check adjustment often.
Section 5 · 5.4.5 – Brake Fading or Failure ↗PDF, 41 MB
On a long or steep downgrade, what is the role of the brakes?

Only a supplement to the braking effect of the engine

The engine does the main work on downgrades, and the brakes only add to it.
Section 5 · 5.4.6 – Proper Braking Technique ↗PDF, 41 MB
Once in the proper low gear on a downgrade, how hard should you apply the brakes?

Just hard enough to feel a definite slowdown

Apply the brakes until you feel a definite slowdown.
Section 5 · 5.4.6 – Proper Braking Technique ↗PDF, 41 MB
On a downgrade, when should you release the brakes?

When speed is about five mph below your safe speed

Release the brakes once you are about five mph below the safe speed.
Section 5 · 5.4.6 – Proper Braking Technique ↗PDF, 41 MB
With proper downgrade braking, about how long should each brake application last?

About three seconds

Each application should last about three seconds.
Section 5 · 5.4.6 – Proper Braking Technique ↗PDF, 41 MB
Your safe speed on a downgrade is 40 mph. When do you apply and release the brakes?

Apply at 40 mph, release at 35 mph

Wait until you reach the safe speed, then brake down to five mph below it and release.
Section 5 · 5.4.6 – Proper Braking Technique ↗PDF, 41 MB
The low air pressure warning comes on. What should you do?

Stop and safely park as soon as possible

There may be an air leak, and controlled braking is possible only while air remains.
Section 5 · 5.4.7 – Low Air Pressure ↗PDF, 41 MB
Why does a heavily loaded vehicle take a long distance to stop on its spring brakes?

The spring brakes do not work on all axles

Spring brakes are not on every axle, so a heavy vehicle needs a long distance to stop.
Section 5 · 5.4.7 – Low Air Pressure ↗PDF, 41 MB
What may happen to lightly loaded vehicles when the spring brakes come on?

They may skid out of control

Lightly loaded vehicles or vehicles on slippery roads may skid when the spring brakes come on.
Section 5 · 5.4.7 – Low Air Pressure ↗PDF, 41 MB
On older vehicles, what might the parking brake control look like?

A round blue knob or a lever

Newer vehicles use a yellow diamond knob, but older ones may have a round blue knob or a lever.
Section 5 · 5.4.8 – Parking Brakes ↗PDF, 41 MB
Why should you not use the parking brakes when the brakes are very hot?

They can be damaged by the heat

Hot brakes can be damaged if the parking brakes are set, so let them cool first.
Section 5 · 5.4.8 – Parking Brakes ↗PDF, 41 MB
Why should you not use the parking brakes when the brakes are very wet in freezing temperatures?

They can freeze so the vehicle cannot move

Wet brakes can freeze in place, so use wheel chocks instead.
Section 5 · 5.4.8 – Parking Brakes ↗PDF, 41 MB
When you cannot use the parking brakes, what holds the vehicle on a level surface?

Wheel chocks

Use wheel chocks on a level surface to hold the vehicle.
Section 5 · 5.4.8 – Parking Brakes ↗PDF, 41 MB
How do you dry wet brakes?

Use the brakes lightly while driving in a low gear

Light braking in a low gear heats and dries the brakes.
Section 5 · 5.4.8 – Parking Brakes ↗PDF, 41 MB
If your vehicle does not have automatic air tank drains, when should you drain the tanks?

At the end of each working day

Drain moisture and oil at the end of every working day, or the brakes could fail.
Section 5 · 5.4.8 – Parking Brakes ↗PDF, 41 MB
What must you do before leaving your vehicle unattended?

Apply the parking brakes or chock the wheels

An unattended vehicle without parking brakes or chocks might roll away.
Section 5 · 5.4.8 – Parking Brakes ↗PDF, 41 MB

Inspecting and using air brakes

Questions and answers

Which inspection procedure should you use on a vehicle with air brakes?

During the engine compartment check, what do you check on a belt-driven air compressor?

Before checking the slack adjusters on s-cam brakes, how should you prepare the vehicle?

How do you check a slack adjuster by hand?

How much may a slack adjuster move where the push rod attaches before it probably needs adjustment?

What is the most common problem found in roadside inspections?

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

Do automatic slack adjusters need to be checked?

A brake with an automatic adjuster has a pushrod stroke past the legal limit. What does that indicate?

What is recommended when brakes with automatic adjusters are found out of adjustment?

Why is manually adjusting an automatic slack adjuster dangerous?

When should an automatic adjuster be adjusted by hand?

How long may a crack in a brake drum be?

What must brake linings not be?

What do you check on the air hoses connected to the brake chambers?

In the final air brake check, at about what pressure should the compressor start pumping?

In the final air brake check, at about what pressure should the compressor stop pumping?

At what engine speed do you check the governor cut-out pressure?

How do you check the governor cut-in pressure?

Why must a governor that does not cut in and out properly be fixed?

For the air leakage test with brakes released, how do you set up?

With the brakes released, what is the most air pressure a single vehicle may lose in one minute?

With the brakes released, what is the most air pressure a combination vehicle may lose in one minute?

For the applied leakage test, how long do you hold the foot brake fully applied?

With the foot brake fully applied, how much pressure loss in one minute is too much for a single vehicle?

With the foot brake fully applied, how much pressure loss in one minute is too much for a combination vehicle?

In the applied leakage test, what is the governor cutoff pressure range given?

Your air loss rate is too high. What should you do?

How do you test the low pressure warning signal?

During the warning signal test, before the tank pressure drops to less than what must the warning come on?

In a dual air system, which tank do you watch in the low pressure warning test?

If the low pressure warning does not work in a single-circuit air system, what could happen?

In the spring brake check, at what pressure should the parking brake valve pop out?

On a tractor-trailer, which valves should pop out when pressure falls during the spring brake check?

In a dual air system at operating rpms, how fast should pressure build from 85 to 100 psi?

If the vehicle has larger than minimum air tanks, can the buildup time be longer?

In single air systems (pre-1975), what is the typical buildup requirement?

At what engine speed is the single air system buildup test done?

Air pressure does not build up fast enough. What should you do?

How do you test the parking brake?

At about what speed do you test the service brakes?

What should you note during the service brake test?

In a normal stop with a manual transmission, when should you push the clutch in?

Without ABS, what happens when your steering wheels lock up?

How does ABS help when it senses impending lockup?

Does having ABS on only the tractor or only one axle still help?

When only the tractor has ABS and the trailer begins to swing out, what should you do?

When only the trailer has ABS, what is less likely?

How should you brake a tractor-trailer combination that has ABS?

When may you fully apply the brakes in an emergency stop?

Your ABS malfunctions. What should you do?

How do you use the controlled braking method?

In controlled braking, what should you do if the wheels lock?

In stab braking, when do you release the brakes?

In stab braking, how long can it take for the wheels to start rolling after you release the brakes?

What is brake lag?

How long does it take air to flow through the lines to the brakes?

Which four factors make up total stopping distance for vehicles with air brakes?

At 55 mph on dry pavement, how much distance does air brake lag add?

At 55 mph with good traction and brakes, what is the total stopping distance with air brakes for an average driver?

What leads to brake fade?

What happens to brake drums when they overheat?

Why can brakes out of adjustment lead to fade on the other brakes?

When can brakes get out of adjustment quickly?

On a long or steep downgrade, what is the role of the brakes?

Once in the proper low gear on a downgrade, how hard should you apply the brakes?

On a downgrade, when should you release the brakes?

With proper downgrade braking, about how long should each brake application last?

Your safe speed on a downgrade is 40 mph. When do you apply and release the brakes?

The low air pressure warning comes on. What should you do?

Why does a heavily loaded vehicle take a long distance to stop on its spring brakes?

What may happen to lightly loaded vehicles when the spring brakes come on?

On older vehicles, what might the parking brake control look like?

Why should you not use the parking brakes when the brakes are very hot?

Why should you not use the parking brakes when the brakes are very wet in freezing temperatures?

When you cannot use the parking brakes, what holds the vehicle on a level surface?

How do you dry wet brakes?

If your vehicle does not have automatic air tank drains, when should you drain the tanks?