Air Brakes CDL (Maryland)

The parking brake must always be used when parked because it provides an additional level of safety and prevents the vehicle from rolling or moving unintentionally. This is especially important when parking on a slope or incline, as it helps to secure the vehicle in place. By engaging the parking brake, the driver ensures that the vehicle remains stationary and reduces the risk of accidents or damage. Therefore, it is necessary to always use the parking brake when parking to ensure the safety of both the vehicle and its surroundings.

Water can freeze in cold weather and cause brake failure. This is because water can enter the brake system and freeze, causing the brake lines to become blocked or the brake fluid to thicken. This can result in decreased brake performance or complete brake failure, making it dangerous to drive in cold weather conditions.

Excessive heat can cause brakes to fade or fail. When brakes get too hot, the friction material can lose its effectiveness, resulting in reduced braking power. This can happen in situations where the brakes are constantly applied for a long period of time, such as when driving downhill or towing heavy loads. The heat generated during braking can also cause the brake fluid to boil, leading to a loss of hydraulic pressure and brake failure. Therefore, it is true that brakes can fade or fail from excessive heat.

The correct answer is 5 mph because releasing the brakes when your speed has been reduced to approximately 5 mph below your "safe" speed allows for a smoother transition and minimizes the risk of skidding or losing control of the vehicle. Releasing the brakes gradually at this point allows the vehicle to regain traction and maintain stability.

The governor is responsible for regulating and controlling the amount of pressure that is put into the tanks. This implies that the statement "The govenor controls how much pressure is put into the tanks" is correct.

The correct answer is 20 to 45 psi. When the air pressure in the tractor or straight truck drops within this range, the spring brakes will fully engage. This is an important safety feature that ensures the vehicle comes to a complete stop in case of a loss of air pressure. If the air pressure drops below 20 psi, it indicates a significant problem with the braking system, and immediate action should be taken to address the issue.

The safety valve is set to open at 150 psi, indicating that when the pressure inside a system reaches or exceeds this threshold, the safety valve will open to release the excess pressure and prevent any potential damage or accidents. This ensures that the system remains within safe operating limits and protects the equipment and personnel involved.

When the air pressure in the tractor and straight truck drops to a range of 20 to 45 psi, the spring brakes will come fully on. This is a safety feature that ensures the brakes engage automatically when there is insufficient air pressure to operate the regular braking system. It helps to prevent accidents and maintain control over the vehicle in case of a loss of air pressure. Therefore, the statement is true.

A heavily loaded vehicle will not take a short distance to stop. The additional weight from the load increases the vehicle's momentum and requires more force to stop. This means that a heavily loaded vehicle will actually take a longer distance to come to a complete stop compared to a vehicle that is not heavily loaded.

When the main air pressure is lost in a vehicle's braking system, the spring brakes are designed to automatically engage. This is a safety feature that ensures the vehicle comes to a stop in the event of a loss of air pressure. The spring brakes use the force of a compressed spring to apply the brakes, preventing the vehicle from moving. Therefore, the statement "When main air pressure is lost, the spring brakes come on" is true.

The correct answer is brake lag. Brake lag refers to the delay in response time for air brakes to engage compared to hydraulic brakes. This delay is caused by the time it takes for air to flow through the brake lines and activate the braking system.

The air compressor should start pumping air when the pressure reaches 100 psi or 100psi. This indicates that the pressure in the system has dropped below the desired level and the compressor needs to kick in to increase the pressure back to the desired level.

The statement is true because the service brake is indeed used for normal braking. The service brake is the primary braking system in a vehicle that is used for regular braking during normal driving conditions. It is operated by the driver and is typically controlled by the brake pedal. The service brake helps to slow down or stop the vehicle safely and effectively.

The explanation for the given correct answer is that in order to test the low pressure warning signal, the engine should be shut off when there is enough air pressure so that the warning signal is not on. Then, the brake pedal should be pumped until the low pressure warning comes on. This process allows for the proper testing of the low pressure warning signal.

The pumping by the air compressor should start at about 100 psi. This means that the air compressor should begin operating when the pressure in the system reaches 100 pounds per square inch. Starting the pumping process at this pressure ensures that there is sufficient air pressure to effectively operate the compressor and provide the necessary power for various applications.

When you have to push harder on the brake pedal to control your speed on a downgrade, it indicates that your brakes are fading. This means that the braking system is losing its effectiveness and not able to generate enough friction to slow down the vehicle properly. As a result, you have to apply more force on the brake pedal to achieve the desired braking effect, which is a clear sign of brake fade.

The correct answer is 45 seconds. This means that when the engine is at operating rpms, the pressure in the dual air systems should build from 85 to 100 psi within 45 seconds. This is an important requirement for the proper functioning of the air systems in the vehicle.

The "cut-out" level refers to the pressure at which the governor stops pumping air. In this case, the correct answer is 125 psi, indicating that the governor will stop pumping air when the pressure reaches 125 pounds per square inch.

The air compressor should stop pumping air when the pressure in the system reaches 125 psi. The answer provided is 125,125 psi, which seems to be a repetition or a typographical error. It is more likely that the correct answer is simply 125 psi, indicating the specific pressure at which the compressor should cease operation.

Parking brakes are designed to hold a vehicle in place when it is parked. Unlike regular brakes that rely on hydraulic or pneumatic pressure, parking brakes use mechanical force to hold the vehicle in position. This is typically achieved by engaging a separate mechanism, such as a lever or pedal, that applies the brakes directly to the wheels. By relying on mechanical force, parking brakes can remain engaged even if there is a failure in the hydraulic or pneumatic systems. Therefore, the statement that parking brakes must be held on by mechanical force is true.

The air brake lag distance at 55 mph on dry pavement adds about 32 feet. This means that when a driver applies the brakes, there is a delay before the brakes fully engage and begin to slow down the vehicle. During this lag time, the vehicle continues to travel at its original speed, resulting in additional distance covered. In this case, the additional distance covered is approximately 32 feet.

Some vehicles may have dual air tanks to ensure that there is enough air pressure to operate the brakes in case of an emergency situation. Having dual air tanks provides redundancy and allows the vehicle to continue moving even if one of the tanks fails or loses pressure. This is especially important for large vehicles such as trucks, buses, or trailers, where the braking system relies on compressed air.

The pressure should take 45 seconds to build up from 85-100 psi in dual air systems. This means that within this time frame, the pressure will gradually increase from 85 psi to 100 psi. It is important to have this information to ensure that the air systems are functioning properly and that the desired pressure is reached within the specified time.

The safety valve will open at 150 psi, indicating that there is a problem. This means that when the pressure inside reaches or exceeds 150 psi, the safety valve will release the excess pressure to prevent any potential damage or danger.

The given statement is false. Perception Distance and Brake Lag Distance are two separate components that contribute to the Total Stopping Distance, but they are not added together. Perception Distance refers to the distance a driver travels from the moment they see a hazard until they fully comprehend it and react. Brake Lag Distance is the distance a vehicle travels from the moment the brakes are applied until the vehicle actually starts to slow down. These two distances are calculated separately and then added to other factors such as braking distance to determine the Total Stopping Distance.

The correct answer is 450 feet. At a speed of 55 mph, the average driver needs approximately 450 feet to bring the vehicle to a complete stop. This distance takes into account the reaction time of the driver and the braking distance required for the vehicle to decelerate safely.

The statement is false because it states that a warning signal must come on before the air pressure in the tanks falls below 75 psi. However, there is no requirement for a warning signal to come on at this specific pressure level.

In an emergency stop, it is not recommended to brake in a way that will turn the vehicle. The correct way to brake in an emergency stop is to apply firm and steady pressure to the brakes without turning the steering wheel. This helps to maintain control of the vehicle and prevent it from skidding or spinning out of control. Braking in a way that turns the vehicle can increase the risk of losing control and causing an accident. Therefore, the statement is false.

The correct answer is brake drum and disks. When the brakes are applied, the brake shoes or pads press against the brake drum or disks. This friction between the brake components slows down the vehicle by converting the kinetic energy into heat energy.

Increasing application pressure to hold the same speed does not necessarily mean that the brakes are not fading. Brake fading is a phenomenon that occurs when the brakes lose their effectiveness due to excessive heat buildup. While increasing application pressure can help maintain speed, it does not guarantee that the brakes are not fading. Brake fading can still occur even with increased pressure if the brakes are not able to dissipate the heat effectively. Therefore, the statement is false.

The explanation for the answer "False" is that while the use of brakes on a long and/or steep downgrade is important, it is not more important than the braking effect of the engine. The engine's braking effect, also known as engine braking, is a crucial component in controlling the speed of a vehicle on a downhill slope. It helps to slow down the vehicle and reduce the strain on the brakes. Therefore, both the use of brakes and the braking effect of the engine are equally important in maintaining control and safety while descending a long and/or steep downgrade.

The "cut-in" level refers to the minimum pressure at which the governor begins pumping air. In this case, the correct answer is 100 psi, meaning that the governor will start pumping air when the pressure reaches or drops below 100 psi.

Before driving a vehicle with a dual air system, it is important to allow time for the air compressor to build up to a minimum of 100 psi of pressure in both the primary and secondary systems. This ensures that there is enough air pressure to properly operate the brakes and other components of the air system, ensuring safe driving conditions.

A straight truck or bus (single vehicle) air brake system cannot leak more than 2 psi per minute with the engine off and the brakes released. This is an important safety requirement to ensure that the air brake system remains functional and does not lose too much pressure when the vehicle is not in use. Excessive air leakage could result in brake failure and compromise the vehicle's ability to stop effectively, posing a risk to both the driver and other road users. Therefore, the maximum allowable leakage rate is limited to 2 psi per minute.

The correct answer is "post trip" because draining air tanks after a trip is necessary to remove any accumulated moisture, oil, or debris that may have entered the tanks during the journey. This helps to prevent corrosion and damage to the air brake system, ensuring its proper functioning and safety for the next trip. Draining the air tanks before a trip is not mentioned as a necessary step in the question, making it an incorrect option.

A combination vehicle (tractor-trailer) air brake system cannot leak more than 3 psi per minute with the engine off and the brakes released. This is because any leak in the air brake system can cause a loss of pressure and result in the brakes not functioning properly. Therefore, it is important to ensure that the air brake system is properly maintained and free from excessive leaks to ensure the safety of the vehicle and its occupants.

When coming down a steep hill, it is important to be in a gear lower than the one you would be in when going up the hill. This is because descending a steep hill puts more strain on the brakes, and being in a lower gear helps to control the speed of the vehicle without relying solely on the brakes. It allows the engine to provide some resistance and helps to prevent the brakes from overheating or wearing out quickly. Therefore, being in a lower gear provides better control and safety while descending a steep hill.

The statement is false because the alcohol evaporator actually adds alcohol to the air system in order to reduce the risk of ice in air brake valves. The alcohol acts as a de-icing agent and helps prevent ice from forming in the valves, ensuring that they function properly.

The correct answer is "before air pressure in the tanks fall below 60 psi." This means that the warning will be activated when the air pressure in the tanks is still above 60 psi. It is important to have this warning system in place to ensure that the air pressure does not drop too low, as it can affect the performance and safety of the vehicle.

When making an emergency stop, it is important to brake in a way that keeps the vehicle in a straight line. This helps to maintain control and stability during the stop. Additionally, braking in a way that allows you to turn if necessary is important because unexpected obstacles or hazards may require you to change direction quickly. By braking in this manner, you are able to stop safely and efficiently while still having the flexibility to maneuver if needed.

Air brakes are not composed of two different braking systems. They are actually composed of a single braking system that uses compressed air to activate the brakes. This system is commonly used in large vehicles such as trucks and buses. The compressed air is stored in a reservoir and when the brake pedal is pressed, the air is released to apply the brakes. Therefore, the correct answer is False.

The given statement is false because the v-belt is not responsible for controlling when the air compressor pumps air into the air storage tanks. The v-belt is a component of the air compressor that transfers power from the motor to the compressor pump, but it does not have any control over the timing or operation of the compressor. The timing and operation of the compressor are typically controlled by a separate control system or mechanism.

The s-cam does not force the brake shoes away from one another and away from the inside of the drums. In fact, the s-cam is responsible for pushing the brake shoes against the inside of the drums, creating friction and causing the vehicle to stop. Therefore, the correct answer is False.

If the brakes are not adjusted properly, both the regular brakes and the emergency/parking brakes will not work correctly. The proper adjustment of brakes is essential for their effective functioning. Therefore, the statement is false.

If the air pressure is removed, the brakes can still be put on. This is because most modern vehicles use hydraulic braking systems, where the brake pedal activates a piston that pushes brake fluid through the brake lines, applying pressure on the brake pads or shoes. The air pressure in the system is only used to assist in the operation of the brakes, but it is not necessary for the brakes to be applied. Therefore, even if the air pressure is removed, the brakes can still be put on using the hydraulic system.

When driving down a long steep hill, using a low gear helps to control the speed of the vehicle and prevent it from gaining too much momentum. Going slow enough ensures that a fairly light and steady use of the brakes will be sufficient to keep the vehicle from speeding up. This approach is safer and more effective than using stab braking or beginning braking when slightly above the "safe" speed. Using the trailer brakes may be necessary if the vehicle is towing a trailer, but it is not mentioned in the question.

The spring brakes will come fully on when the air pressure in the system reaches a range of 20 to 45 psi. This means that once the pressure drops below 20 psi, the spring brakes will engage and prevent the vehicle from moving. Similarly, once the pressure is restored and reaches 45 psi, the spring brakes will release and allow the vehicle to move again. Therefore, the correct answer options indicate the acceptable range of air pressure for the spring brakes to fully engage.

The correct answer is Perception Distance + Reaction Distance + Brake Lag Distance + Effective Stopping Distance. This answer includes all the components that make up the total stopping distance of a vehicle. Perception distance is the distance traveled while the driver recognizes a hazard, reaction distance is the distance traveled while the driver reacts to the hazard, brake lag distance is the distance traveled while the brakes are applied, and effective stopping distance is the distance traveled until the vehicle comes to a complete stop.