CSLB General Building (B) — All Questions

During a walk-around inspection, how do you check manual slack adjusters on S-cam brakes?

• a.By listening for air leaks at the wheel
• b.By measuring the air pressure at each chamber
• c.By pulling hard on each one and checking that it moves no more than about one inch✓
• d.By spinning the wheel by hand

With the parking brakes released and wheels chocked, pull hard on each manual slack adjuster you can reach. If it moves more than about one inch from where the pushrod attaches, it is probably out of adjustment. Brakes that are out of adjustment do not work properly and are unsafe.

When checking the air compressor during inspection, what should you look at if it is belt-driven?

• a.The condition and tightness of the compressor drive belt✓
• b.The color of the compressed air
• c.The reading on the speedometer
• d.The temperature of the parking brake knob

If the air compressor is driven by a belt, you should check the condition and tightness of the belt during your inspection. A loose or worn belt can slip and keep the compressor from building enough pressure. A properly tensioned belt helps the compressor keep the system charged.

What is the correct way to begin the air brake check for build-up rate in a dual air system?

• a.Drain all the tanks completely first
• b.With the engine at operating rpm, check that pressure builds from about 85 to 100 psi within about 45 seconds✓
• c.Apply the parking brake and rev the engine
• d.Disconnect the trailer air lines

In a dual air system, with the engine at operating rpm, the pressure should build from about 85 to 100 psi within about 45 seconds. If air pressure does not build up fast enough, your pressure may drop too low during driving, requiring you to stop and wait to build air. Slow build-up indicates a problem to be fixed.

How do you test the low-pressure warning signal?

• a.By draining the tanks while driving
• b.By pulling on the slack adjusters
• c.By turning the electrical power on and fanning off air until the warning activates✓
• d.By revving the engine to build pressure

With the key on and enough air in the system, step on and off the brake pedal to reduce tank pressure (this is called fanning off the air). The low air pressure warning signal must come on before the pressure drops below 60 psi. If it does not, the warning is faulty and must be repaired.

At what pressure should the spring brakes come on automatically during the continued-air-loss test?

• a.Below 90 psi
• b.Below 75 psi
• c.Below 100 psi
• d.In the range of about 20 to 45 psi✓

Continuing to fan off the air, the spring brakes should come on automatically when tank pressure falls to the manufacturer's specified level, usually in the range of about 20 to 45 psi. On a tractor-trailer, you may hear the parking brake valve pop out. This confirms the automatic emergency braking works.

How do you perform the static leakage (applied pressure) test on a straight truck with air brakes?

• a.With a fully charged system, release the brakes, turn off the engine, apply full brake pressure, and watch that the drop does not exceed the allowed limit✓
• b.Drain the tanks and check that they refill on their own
• c.Drive at 20 mph and slam on the brakes
• d.Disconnect the trailer and check the gladhands

With the air system fully charged (about 125 psi), turn off the engine, release the parking brake, and hold the brake pedal down (fully applied). After the initial pressure drop stabilizes, the air pressure should not drop more than 3 psi in one minute for a straight truck (4 psi for a combination). A greater loss means there is a leak that must be repaired.

For a single vehicle (straight truck), what is the maximum allowable air pressure loss in one minute with the brakes applied?

• a.1 psi
• b.3 psi✓
• c.6 psi
• d.10 psi

For a single vehicle, air pressure should not drop more than 3 psi in one minute when the brakes are fully applied and the engine is off. For a combination vehicle, the limit is 4 psi in one minute. A larger loss indicates a leak too big to be safe.

With the engine off and brakes released, what is the maximum allowable air leakage per minute for a straight truck?

• a.1 psi
• b.3 psi
• c.2 psi✓
• d.5 psi

With the engine off, the air pressure should not drop more than 2 psi in one minute for a single vehicle with the brakes released. For a combination vehicle, the limit is 3 psi per minute. Excessive leakage means the system cannot hold pressure and must be repaired.

How should you test that the service brakes are working before driving?

• a.By pulling on the slack adjusters
• b.By listening for the compressor to cut out
• c.By draining the air tanks
• d.By moving the vehicle slowly and firmly applying the brake pedal to feel for a proper stop✓

After building normal air pressure, move the vehicle forward slowly at about 5 mph and firmly apply the brake pedal. The vehicle should stop and you should not feel any unusual pulling to one side, delay, or unusual feel in the pedal. Any problem should be fixed before driving.

How do you test that the parking (spring) brakes hold?

• a.Set the parking brake and gently pull forward in low gear to confirm it holds the vehicle✓
• b.Rev the engine with the brakes off
• c.Drain the tanks and drive forward
• d.Apply the trailer hand valve only

With the vehicle stopped, apply the parking brake, then gently try to move forward in a low gear against the parking brake. The parking brakes should hold the vehicle in place. If they do not, they are faulty and must be repaired before driving.

What should you check about the brake drums or discs during a walk-around inspection?

• a.That they are painted a bright color
• b.That they are not cracked and have no loose or missing parts✓
• c.That they spin freely by hand
• d.That they contain compressed air

Check that brake drums or discs are not cracked and that there are no loose, missing, or broken parts such as springs. Cracks longer than a certain length can cause brake failure. Also make sure oil or grease is not on the linings, which would reduce braking.

During inspection, brake linings (shoes or pads) should be checked for what?

• a.Correct color and shine
• b.Proper air pressure
• c.Excessive wear and to make sure they are not soaked with oil or grease✓
• d.Frozen water inside them

Brake shoes or pads should not be worn dangerously thin, and they should be free of oil or grease. Linings that are too thin or contaminated cannot provide enough friction to stop the vehicle. Cracked, broken, or missing linings are also out-of-service conditions.

When inspecting the air lines and hoses, what should you look for?

• a.Bright paint and clean labels
• b.How fast air moves through them
• c.Their exact length in feet
• d.Cracks, cuts, worn spots, and air leaks✓

Air lines and hoses should be checked for cracks, cuts, worn spots, and signs of leaks. Damaged lines can burst and cause a loss of air pressure. Listen for hissing that would indicate escaping air.

Why should you drain the air tanks and check for oil or water before a trip if the tanks do not have automatic drains?

• a.To remove moisture and oil that could damage the brakes or freeze✓
• b.To increase the air pressure
• c.To speed up the compressor
• d.To test the parking brake knob

Air tanks collect water and compressor oil, so tanks without automatic drains must be drained manually. Removing this buildup prevents freezing in cold weather and protects brake components. A lot of oil in the tanks can indicate a compressor problem.

During the pre-trip air brake check, when should you check that the pushrod stroke is not too long?

• a.Only after the trip is finished
• b.While inspecting the brake chambers and slack adjusters, since too long a stroke means brakes are out of adjustment✓
• c.Only when the engine is off and cold
• d.Never, because it cannot be checked

When brakes are applied, the pushrod should not travel too far out of the brake chamber. Excessive pushrod stroke means the brakes are out of adjustment and may not stop the vehicle effectively. This is related to checking slack adjusters and is a common out-of-service violation.

What does it mean if the low-pressure warning stays on after you start building air pressure?

• a.The brakes are fully adjusted
• b.The parking brake is released
• c.The system pressure is still too low, or the warning device is faulty✓
• d.The compressor has cut out normally

The low-pressure warning should turn off once air pressure rises above about 60 psi. If it stays on, either the system has not yet built enough pressure or the warning device or gauge is malfunctioning. You should not drive until the cause is found and pressure is normal.

Before the leak-down (static) tests, to what pressure should the air system be brought?

• a.About 20 psi
• b.About 45 psi
• c.About 60 psi
• d.Governor cutout, about 125 psi (fully charged)✓

Before performing the applied and released leak-down tests, the system should be fully charged to about governor cutout pressure (around 125 psi). Starting from full charge gives an accurate measure of how much air leaks out over one minute. Testing from a low pressure would not reveal the true leak rate.

What is the correct order for the brake system portion of a pre-trip inspection regarding air build-up?

• a.Build pressure to cutout, then test build-up rate, warning signal, spring brake activation, and leak rates✓
• b.Test the parking brake first, then drain all tanks
• c.Drive the vehicle, then check the compressor
• d.Apply the hand valve, then check the tires

You first let the system build to governor cutout to confirm the compressor and governor work. Then you check the build-up rate, test the low-pressure warning, continue fanning to confirm the spring brakes apply, and finally check the leak rates. Doing the checks in order confirms each safety feature works.

If you find a lot of oil in the drained air from the tanks, what could this indicate?

• a.The brakes are properly adjusted
• b.A possible problem with the air compressor✓
• c.The tanks are overfilled with air
• d.The parking brakes are engaged

Finding a lot of oil in the air tanks can indicate a problem with the air compressor, such as worn parts allowing oil to pass through. This should be checked by a mechanic. Some oil is normal, but a large amount is a warning sign.

Why is it important to check that the governor cuts the compressor in and out at the correct pressures?

• a.To keep the tires properly inflated
• b.To keep the speedometer accurate
• c.So the system stays within a safe operating pressure range for braking✓
• d.To reduce fuel consumption

The governor must cut out at about 125 psi and cut in at about 100 psi to keep tank pressure in the safe operating range. If it cuts out too high, the safety relief valve may release air; if it cuts in too low, the brakes may not have enough air. Correct settings keep braking reliable.