CDL Air Brakes Test flashcards

A valve that controls the air pressure to the spring brakes, applying or releasing the parking brake.

• Typically a push-pull knob on the dashboard.
• Pushed in to release parking brake (charges spring brakes with air).
• Pulled out to set parking brake (releases air from spring brakes, allowing them to engage).
• Should automatically 'pop out' when air pressure drops below a critical level (20-45 psi).

Memory trick: Pull to Park, Push to Go, Pop-out says 'Stop, no go!'

Valves located at the bottom of air storage tanks used to manually or automatically remove accumulated moisture, oil, and contaminants.

• Essential for system health and longevity.
• Should be drained daily or as recommended.
• Prevent freezing in lines and corrosion of components.

Memory trick: Drain the tanks, keep the air clean and sane!

Deterioration of parts inside the air compressor (e.g., piston rings, intake/exhaust valves) that reduces its efficiency and ability to compress air, leading to slow pressure build-up.

• Results in longer build-up times.
• Can be a progressive issue.
• Requires compressor rebuild or replacement.
• Often accompanied by increased oil consumption or unusual noises.

Memory trick: Piston's weak, valves may leak, compressor's tired, a slow air peak.

A condition where the unloader valves in the air compressor do not properly seal, preventing the compressor from fully 'unloading' and resting at cut-out pressure.

• Causes compressor to work continuously against residual pressure.
• Leads to overheating and accelerated wear of compressor.
• Often indicated by a faint hiss at the compressor head when system is at full pressure.

Memory trick: Unloader Leaks, Compressor Creaks, Life Decreases.

The brake pedal (foot) valve, also known as the treadle valve, controls the flow of air from the air tanks to the service brake chambers, both applying and releasing the brakes proportionally to pedal pressure.

• Sends air to both primary and secondary brake systems.
• Contains exhaust ports for brake release.
• Proportional control: more pedal, more air pressure.

Memory trick: Quick exhaust, quick release.

Degradation of internal components (e.g., piston rings, seals) within the air compressor, leading to oil contamination of the air system.

• Results in oily water in air tanks.
• Reduces compressor efficiency.
• Can contaminate and damage other air system components.

Memory trick: Water is normal, but oil is a compressor's 'soil'!

A valve found on some older vehicles that allows the driver to reduce air pressure to the front brakes (e.g., by half) for driving on slippery surfaces.

• Typically has 'normal' and 'slippery' (or 'low') settings.
• Reduces front braking power in 'slippery' mode.
• Should be in 'normal' for most driving conditions.

Memory trick: Slippery Setting = Soft Front Stop.

Erratic or rapid movement of the air pressure gauge needle, typically indicating a problem with the gauge itself or its supply line rather than the main system pressure.

• Often caused by a leak or restriction in the gauge's dedicated air line.
• Can also be caused by a faulty gauge internal mechanism.
• Does not necessarily mean the main air system pressure is fluctuating.
• Requires inspection of the gauge and its connections.

Memory trick: Gauge needle dances, not a chance, check the line, give it a glance.

The air compressor must be able to build air pressure from 85 psi to 100 psi within 45 seconds for a properly functioning air brake system.

• Standard applies at engine's operating RPM.
• Ensures adequate air supply for safe braking.
• Failure to meet rate indicates potential compressor or system issues.

Memory trick: Fast air build-up keeps you on the road, slow build-up means trouble could explode.

An air compressor with internal wear or damage that prevents it from generating or maintaining sufficient air pressure, even when running continuously.

• Runs constantly without reaching full pressure.
• Internal components (e.g., piston rings) are worn.
• Requires replacement or overhaul.

Memory trick: Compressor Cries, but Can't Create enough pressure.

Air lines to the service brake chambers that are partially blocked or kinked, preventing rapid air flow and causing slow application or release of the service brakes.

• Can cause brakes to drag or apply unevenly.
• Increases stopping distance and brake wear.
• Requires inspection and replacement of affected lines.
• Distinguished from slack adjuster issues by proper adjustment.

Memory trick: Air's stuck, not flowing free, slow release, for all to see.

Powerful springs that apply the brakes when air pressure is removed or drops below a critical level. They serve as both an emergency brake and a parking brake.

• Held 'off' by air pressure.
• Engage automatically if air pressure fails (emergency).
• Engage when parking brake control is pulled (parking).

Memory trick: Springs Bring Brakes On for Parking and Peril.

An unintended escape of compressed air from the brake system, leading to more frequent air compressor cycling and potential pressure loss.

• Compressor cycles more often.
• System pressure drops even without brake use.
• Needs immediate repair to prevent brake failure.

Memory trick: Leak leads to Low pressure, Compressor keeps on working.

Gauges on the dashboard that display the current air pressure in the primary and secondary air storage tanks of a commercial vehicle's air brake system.

• Indicate available braking air.
• Typically one gauge for each tank (primary/secondary).
• Crucial for pre-trip inspections and continuous monitoring.

Memory trick: Gauges Guard Global Air Supply.

A 'spongy' or soft brake pedal, even with normal air pressure, often indicates excessive wear in the foundation brake components, requiring greater pedal effort and travel to achieve effective braking.

• Includes wear on linings, drums, slack adjusters.
• Reduces braking efficiency.
• Requires more air volume to compensate for lost travel.

Memory trick: Pedal feels like sponge? Foundation brakes are due for a plunge!

One-way valves in a dual air brake system that separate the primary and secondary air circuits, ensuring that a leak in one system does not completely drain the other.

• Prevents total air loss from a single fault.
• Allows air to flow into tanks, but not back out.
• Failure can lead to one tank not pressurizing.

Memory trick: Check Valves Control Flow, Keeping Tanks Apart.

A characteristic rapid pulsing sensation felt in the brake pedal when the Anti-lock Braking System (ABS) is actively modulating brake pressure to prevent wheel lock-up.

• Normal behavior during hard braking on slippery surfaces.
• Indicates ABS is functioning as designed.
• Should not be confused with brake system malfunction.

Memory trick: ABS Pushes Back To Keep You Straight.

The air compressor governor controls when the air compressor pumps air into the air storage tanks. It has 'cut-in' and 'cut-out' pressures.

• Set to cut-out around 125 psi and cut-in around 100 psi.
• Stops the compressor when tanks are full ('cut-out').
• Starts the compressor when tank pressure drops ('cut-in').

Memory trick: Governor's got the compressor's 'go' and 'stop' signals.

A diagnostic sequence performed by the Anti-lock Braking System (ABS) computer upon vehicle start-up, indicated by the ABS light illuminating briefly and then turning off.

• Normal operation: Light comes on, then goes off.
• Light staying on indicates a fault.
• Confirms ABS system is operational.

Memory trick: Light On, Light Off = All Good, Boss.

A filter located at the air intake of the compressor, designed to remove dust, dirt, and other particulate matter from the air before it is compressed and sent into the air brake system.

• Protects compressor internal components from abrasive wear.
• Ensures clean air enters the system, preventing contamination.
• Requires regular inspection and replacement.

Memory trick: Clogged Filter = Compressor's Flogging!

Components that adjust the distance between the brake shoes and the brake drum, ensuring proper brake stroke and efficient braking.

• Automatic slack adjusters maintain proper clearance.
• Excessive slack leads to 'spongy' brakes and longer stopping distances.
• Must be checked during pre-trip inspection.

Memory trick: Slack = Slow Stops.

Slack adjusters automatically or manually adjust the distance between the brake shoe and the drum to compensate for brake lining wear, ensuring proper brake application with minimal pedal travel.

• Maintain correct brake pushrod stroke.
• Prevent excessive brake pedal travel.
• Critical for efficient and safe braking.

Memory trick: Too much pedal travel? The slack's too loose, time to adjust the juice!

A constant loss of air pressure from the air brake system, often indicated by frequent cycling of the air compressor or a noticeable hiss.

• Can be caused by loose fittings, cracked lines, faulty diaphragms, etc.
• Leads to increased compressor wear and reduced system efficiency.
• Must be located and repaired promptly for safety.

Memory trick: Frequent pump means a hidden hump (leak)!

A device used in older air brake systems to introduce alcohol vapor into the air lines to prevent moisture from freezing.

• Used primarily in cold climates.
• Replaced by air dryers in newer vehicles.
• Requires periodic refilling with special alcohol.

Memory trick: Alcohol's sip keeps the air lines from a frozen dip!

The parking brake control knob in an air brake system controls the application and release of the spring brakes, which function as parking and emergency brakes.

• Pulled out = spring brakes engaged (parking/emergency).
• Pushed in = spring brakes released (air pressure holds them off).
• Directly controls air pressure to spring brake chambers.

Memory trick: Pull to park, push to go.

The ABS indicator light (often amber) illuminates briefly when the ignition is turned on as a self-test and should then turn off. If it stays on, it signals a malfunction in the Anti-lock Braking System.

• Indicates an ABS fault, not conventional brake failure.
• Conventional brakes will still work.
• Should be addressed by qualified personnel.

Memory trick: Light on, something's wrong!

An air brake system with two independent air brake circuits (typically one for the front axle and one for the rear axle), each with its own air tank, lines, and components, designed for redundancy and safety.

• Provides a safety margin if one system fails.
• Front and rear brakes operate independently.
• Requires separate gauges for each system.

Memory trick: One Low, One High? Must Be a Leak or a Block.

A condition where the brake pedal must be pushed down further than normal to engage the service brakes effectively, despite adequate air pressure.

• Often indicates excessive slack in the foundation brakes.
• Can be caused by improperly adjusted slack adjusters or worn brake components.
• Reduces braking efficiency and increases stopping distance.

Memory trick: Long Pedal, Long Slack, Long Stop.

The low air pressure warning system alerts the driver when air pressure in the primary or secondary tank falls below 60 psi (or half the governor cut-out pressure, whichever is lower).

• Must activate at 60 psi or higher.
• Usually a red light and an audible buzzer.
• Indicates insufficient air for safe braking.

Memory trick: Sixty psi, safety's key!

A malfunction in the foot-operated valve that controls air to the service brake chambers, leading to unintended air flow or leakage.

• Can cause continuous air leak at brake chambers.
• Leads to rapid air pressure drop.
• Affects service brake operation.

Memory trick: Foot Valve Failing, Air is Ailing.

Air storage tanks must be drained daily to remove water and oil that condense from compressed air, preventing system damage and freezing.

• Water and oil are normal byproducts of air compression.
• Draining prevents corrosion, freezing, and brake system contamination.
• Automatic drain valves exist, but manual checks are still important.

Memory trick: Wet tank, bad dryer; clean tank, good dryer.

A blockage or restriction in the air compressor's intake system (e.g., a dirty air filter) that reduces the amount of air available for compression, leading to slow pressure build-up.

• Causes the compressor to work harder.
• Increases the time required to reach cut-out pressure.
• Can lead to compressor overheating and premature wear.
• Often indicated by a drop in air delivery volume.

Memory trick: When the compressor's breathing is hard, pressure builds slow and scarred.

Wear in components like brake linings, drums, or slack adjusters in the foundation brakes can lead to reduced braking effectiveness and a 'spongy' feeling in the brake pedal.

• Includes brake shoes, drums, slack adjusters, brake chambers.
• Wear increases required pedal effort/travel.
• Causes reduced braking efficiency.

Memory trick: Worn parts make the pedal Weak, requiring more work.

The degradation of the air tank material due to rust and pitting, typically caused by moisture exposure or lack of maintenance.

• Weakens the tank walls, compromising structural integrity.
• Increases the risk of catastrophic tank rupture.
• Requires immediate attention and potential tank replacement.

Memory trick: Rusting Tanks, High Risk, Big Bang.

The opening of the safety relief valve on an air tank to release excessive air pressure, protecting the system from over-pressurization and potential rupture.

• Typically set to open at 150 psi.
• Indicates a failure in the air compressor governor or unloader valves.
• Continuous activation is a serious safety concern.
• Requires immediate diagnosis and repair of the compressor/governor system.

Memory trick: Hissing valve, pressure so high, governor failed, a dangerous sigh.

A pressure-activated electrical switch in an air brake system that illuminates the vehicle's stop lights when the service brakes are applied.

• Ensures other drivers are aware of braking.
• Located near the brake pedal or in the air line to the service brakes.
• Essential for safety and legal compliance.

Memory trick: Brake light switch, a bright safety stitch!

A pressure relief device on air tanks designed to protect the air brake system from over-pressurization.

• Opens automatically if pressure exceeds 150 psi.
• Prevents damage to components and potential tank rupture.
• Should 'pop off' if governor fails to cut out compressor.

Memory trick: Safety valve is the system's pressure guardian.

Excessive heat buildup in the brake drums and linings, often indicated by discoloration, cracking, or glazing, leading to reduced braking power.

• Caused by prolonged or heavy braking.
• Results in brake fade and damage.
• Discoloration (blue/purple) and cracking are key signs.

Memory trick: Blue Drums = Burnt Brakes.

A pressure relief device on each air storage tank designed to protect the tank and system from dangerously high air pressures.

• Opens automatically if pressure exceeds 150 psi (typically).
• Prevents tank rupture.
• Releases excess air with a loud hiss.

Memory trick: Safety Saves, Sounding an air-pressure alarm.

Air storage tanks are critical pressure vessels whose structural integrity must be maintained. Any physical damage, such as dents or corrosion, requires professional inspection and repair/replacement.

• High-pressure vessels, critical safety component.
• Dents can compromise structural integrity.
• Requires inspection by qualified personnel.

Memory trick: Dent's Danger: Don't Delay, Diagnose Damage.

The air compressor governor regulates the air compressor, causing it to stop pumping air into the tanks when pressure reaches the 'cut-out' setting (typically 125 psi).

• Controls compressor on/off cycle.
• Cut-out: Stops compressor (e.g., 125 psi).
• Cut-in: Starts compressor (e.g., 100 psi).

Memory trick: Governor: it's the 'boss' of the compressor.

Deterioration of air tank material (typically steel) due to rust and pitting, which can weaken the tank and lead to dangerous failure under pressure.

• Caused by moisture accumulation and environmental exposure.
• Interior corrosion is often worse than exterior.
• Compromises tank integrity and safety.
• Requires professional inspection and potential replacement.

Memory trick: Rust on the tank, a dangerous prank, get it checked by a mechanic, or you're in a panic.

A safety system (light and buzzer) that alerts the driver when air pressure in the service brake system drops below a safe operating level, typically 60 psi or 55 psi.

• Mandatory safety feature.
• Activates a red warning light and an audible buzzer.
• Different from the pressure at which spring brakes engage (20-45 psi).

Memory trick: Low pressure, loud warning- don't ignore the alarm!

The time it takes for the air compressor to increase air pressure from 85 psi to 125 psi, which must be within specific regulatory limits (typically 45 seconds or less for dual systems).

• Tested during pre-trip inspection.
• Indicates compressor health and system leaks.
• Failure to meet minimum rate requires repair.
• Specific times can vary slightly by vehicle and jurisdiction (e.g., 45 sec for dual, 60 sec for older/larger).

Memory trick: Pressure climbing, time is ticking, safety's on the line.

Valves in a dual air brake system that prevent air from flowing from one tank or circuit to another, ensuring independent operation and preventing total air loss from a single leak.

• Maintains separate pressure in primary and secondary circuits.
• Allows air to flow in one direction only.
• Critical for safety in case of a single circuit failure.

Memory trick: Dual tanks, separate paths, check valves keep them apart!

The parking brake control valve controls the flow of air pressure to the spring brake chambers. When released, it allows air pressure to push against the spring, releasing the brakes.

• Spring brakes are 'spring-applied, air-released'.
• Air pressure overcomes spring force to release brakes.
• Insufficient air pressure or a faulty valve prevents full release.

Memory trick: Spring brakes stuck? Air pressure's low, or the valve won't flow!

The parking brake on commercial vehicles uses spring brakes that are held in the 'off' position by air pressure and apply automatically when air pressure is lost or the parking brake control is activated.

• Primarily uses spring brakes.
• Must hold the vehicle on a grade.
• Released by air pressure, applied by spring force.

Memory trick: Springs are strong, air keeps them calm.

Foundation brakes are the mechanical components at each wheel that convert air pressure into friction to stop the vehicle, including drums, shoes, and linings.

• Directly stop the wheels.
• Consist of drums/rotors, shoes/pads, and linings.
• Actuated by brake chambers.

Memory trick: Foundation: the 'feet' that stop the vehicle.

A procedure to test for air leaks in a dual air brake system, performed by observing pressure drop in each isolated air tank with the engine off and brakes released. Maximum allowable leakage rates are specified by regulations.

• Vehicle must be fully charged (125 psi).
• Engine off, parking brake on, brakes released (no foot pressure).
• Combination vehicle max leak rate: 3 psi/min; single vehicle max leak rate: 2 psi/min.

Memory trick: One Tank Drops, Other Holds? It's a Leak's Old Hold!

These valves allow the air compressor to run without pumping air into the air tanks once the system reaches its maximum pressure, preventing over-pressurization.

• Controlled by the air compressor governor.
• Open when cut-out pressure is reached.
• Close when cut-in pressure is reached.
• Reduce wear on the compressor and prevent system over-pressurization.

Memory trick: Unload the pressure, let the compressor rest, but keep it ready for the next test.

The air compressor governor uses an unloader valve (or mechanism) to stop the compressor from pumping air into the tanks once the cut-out pressure is reached. If stuck open, it continuously vents compressed air.

• Controls compressor's pumping and idling states.
• Unloader valve opens to vent air when tanks are full.
• Stuck open causes continuous air venting and no pressure buildup.

Memory trick: Hissing governor, no pressure gain.

Spring brakes are designed to engage automatically when air pressure falls below a critical level, serving as both parking and emergency brakes.

• Engage at 20-45 psi.
• Released by air pressure, applied by spring force.
• Must be tested by draining air to verify automatic application.

Memory trick: Spring brakes: no air, they're there!

The mechanical components at each wheel end (e.g., brake shoes/linings, drums, slack adjusters, brake chambers) that physically stop the vehicle. Proper slack adjustment is critical for effective braking.

• Slack adjusters maintain correct clearance between linings and drums.
• Excessive slack leads to long pedal travel and reduced braking force.
• Manual and automatic slack adjusters require proper inspection and maintenance.

Memory trick: Soft Pedal = Slack Problem.

ABS is a safety system that prevents wheel lock-up during braking, allowing the driver to maintain steering control.

• Prevents skidding.
• Enhances vehicle control.
• Works by rapidly modulating brake pressure to individual wheels.

Memory trick: ABS: Always Better Steering.

A condition where the air compressor runs continuously but fails to build or maintain adequate air pressure (e.g., above 80 psi), typically indicating a severe air leak in the brake system.

• Compressor working hard but losing the battle.
• Indicates a potentially dangerous system integrity failure.
• Requires immediate investigation and repair.

Memory trick: Compressor's Chugging, Pressure's Lagging? A Leak is Bragging!

Frequent cycling of the air compressor without brake application is a key symptom of a continuous air leak within the air brake system, as the compressor works harder to maintain lost pressure.

• Indicates pressure loss in the system.
• Can be internal or external leak.
• Requires immediate investigation and repair.

Memory trick: Compressor's working hard? A hidden leak is playing its card!

During normal service brake application, a small amount of air pressure is consumed, causing a temporary gauge drop, which the air compressor quickly replenishes.

• Minor pressure drop (2-4 psi) is normal upon brake application.
• Air compressor should quickly recover pressure.
• Indicates a healthy, sealed system.

Memory trick: Pressure dips, then Puffs back, a normal brake dance.

A diagnostic symptom where the air compressor runs constantly but fails to reach the upper pressure limit (cut-out pressure) in the air tanks.

• Often indicates a significant air leak in the system.
• Could also be a severely worn compressor, but leak is more common.
• Safety valve not opening rules out overpressure.

Memory trick: Constant Pump, No Peak, Means Leak.

The distance the brake chamber's pushrod moves when the service brakes are fully applied. This stroke directly indicates the adjustment of the foundation brake; excessive stroke means the brake is out of adjustment.

• Measured during a brake test.
• Maximum allowable stroke varies by brake chamber size.
• Excessive stroke leads to reduced braking power and potential brake fade.

Memory trick: Long Stroke, Weak Brake.

The low air pressure warning system alerts the driver when tank pressure drops below a safe operating level, while spring brakes automatically apply at a lower, critical pressure to stop the vehicle.

• Warning activates at/above 60 psi.
• Spring brakes apply automatically between 20-45 psi.
• These are critical safety features.

Memory trick: Warning first, then Wheels stop, when air is low.