MCFRS Engine Module 1: Exhaust Systems
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Questions and Answers

What is the primary purpose of Diesel Exhaust Fluid (DEF)?

  • To reduce diesel fuel consumption
  • To improve engine performance
  • To increase fuel efficiency
  • To break down nitrogen oxide emissions into nitrogen and water (correct)

    • What is the composition of Diesel Exhaust Fluid (DEF)?

  • 40% urea and 60% de-ionized water
  • 25% urea and 75% de-ionized water
  • 32.5% urea and 67.5% de-ionized water (correct)
  • 50% urea and 50% de-ionized water

    • What happens when the DEF tank reaches empty?

  • The vehicle's power will be reduced automatically (correct)
  • The vehicle's fuel efficiency will decrease
  • The vehicle's emission control system will fail
  • The vehicle's engine will shut off

    • Why should the DEF tank not be continuously topped off?

    <p>There is no need to continuously top off the DEF tank</p> Signup and view all the answers

    What is the purpose of the Diesel Particulate Filter (DPF)?

    <p>To reduce diesel particulate matter</p> Signup and view all the answers

    Where is the DEF level indicator typically located?

    <p>On the dashboard, near the fuel level indicator</p> Signup and view all the answers

    What should be done with DEF that shows signs of crystallization?

    <p>Do not use it and request a new container</p> Signup and view all the answers

    What is the effect of DEF on aluminum?

    <p>It is corrosive to aluminum</p> Signup and view all the answers

    What is the purpose of the automatic traction control function?

    <p>To monitor wheel speeds and apply braking to a spinning drive wheel</p> Signup and view all the answers

    What should a driver do if they get stuck and the automatic traction control is cutting the throttle?

    <p>Engage the 'mud and snow' switch</p> Signup and view all the answers

    Why is it important to inspect emergency vehicles prior to each shift?

    <p>To prevent accidents caused by lack of maintenance or vehicle malfunction</p> Signup and view all the answers

    Who is responsible for ensuring the mechanical safety of an emergency vehicle?

    <p>The driver</p> Signup and view all the answers

    What should a driver do if they suspect a problem with their vehicle?

    <p>Do not drive the vehicle and report the issue</p> Signup and view all the answers

    What is the purpose of recording maintenance, repairs, and inspections?

    <p>To track vehicle history</p> Signup and view all the answers

    How many core areas are inspections typically broken down into?

    <p>9</p> Signup and view all the answers

    What is the result of regular preventive maintenance inspections?

    <p>Identification of problems and temporary repairs</p> Signup and view all the answers

    What is the freezing point of DEF?

    <p>12°F</p> Signup and view all the answers

    What happens when sufficient particulate has accumulated in the system?

    <p>The DPF indicator illuminates</p> Signup and view all the answers

    When does regeneration of the DPF occur?

    <p>When the vehicle is at highway speeds for over 20 minutes</p> Signup and view all the answers

    What is the purpose of the differential in the driveline?

    <p>To allow wheels on the same axle to turn at different speeds</p> Signup and view all the answers

    What is the result of a faulty exhaust system?

    <p>Emission of poisonous fumes into the crew area</p> Signup and view all the answers

    What is the primary function of the transmission?

    <p>To change the gear ratio</p> Signup and view all the answers

    What is the purpose of the driveshaft?

    <p>To connect the transmission to the differential</p> Signup and view all the answers

    Why is personal protective equipment not necessary when handling DEF?

    <p>Because DEF is designed to be safe to handle</p> Signup and view all the answers

    What should a driver do when an emergency vehicle's wheels lock during braking?

    <p>Immediately release the brake pedal and steer with the skid</p> Signup and view all the answers

    What is the main purpose of covering the brake pedal while driving?

    <p>To decrease the reaction time when braking</p> Signup and view all the answers

    What is the single most important aspect of braking safely?

    <p>Allowing enough space to identify the need to brake</p> Signup and view all the answers

    What should a driver do when approaching an intersection or traveling against traffic?

    <p>Cover the brake pedal</p> Signup and view all the answers

    What should a driver do when using anti-lock braking systems (ABS)?

    <p>Apply steady pressure to the brake pedal</p> Signup and view all the answers

    What is the purpose of threshold braking in vehicles with air brakes?

    <p>To avoid locking the wheels</p> Signup and view all the answers

    What should a driver do when an emergency vehicle's wheels lock during braking with ABS?

    <p>Release the brake pedal and steer with the skid</p> Signup and view all the answers

    What is the benefit of increasing the look-ahead distance in heavy apparatus?

    <p>Reduced need to use the service brakes</p> Signup and view all the answers

    What should you do to slow down the vehicle while approaching a curve at high speed?

    <p>Allow natural friction of the engine and compression to slow the vehicle down</p> Signup and view all the answers

    What is the result of overheating in the brake system?

    <p>Reduced braking effectiveness</p> Signup and view all the answers

    When should you accelerate out of a curve?

    <p>After the apex has been reached and the vehicle is on a straight path</p> Signup and view all the answers

    What is a key consideration when stopping at higher speeds?

    <p>More stopping distance is required</p> Signup and view all the answers

    Why should you downshift the transmission when braking at high speeds?

    <p>To reduce the stress on brake systems</p> Signup and view all the answers

    What is the primary responsibility of an emergency vehicle driver?

    <p>To ensure the safety of passengers and arrive safely at the incident</p> Signup and view all the answers

    What should you do when driving in adverse conditions?

    <p>Adjust driving techniques and auxiliary braking systems</p> Signup and view all the answers

    What is the difference between drum brakes and disc brakes?

    <p>Drum brakes are more prone to overheating</p> Signup and view all the answers

    What is the purpose of spring brakes in an air brake system?

    <p>To hold the vehicle in place when parked</p> Signup and view all the answers

    What happens when the air pressure in the air tanks falls below 60 psi?

    <p>A warning signal is sent to the driver</p> Signup and view all the answers

    What is the purpose of the brake light switch in an air brake system?

    <p>To warn drivers behind you that you are applying the brakes</p> Signup and view all the answers

    What should you avoid doing when the spring brakes are on?

    <p>Pushing the brake pedal down</p> Signup and view all the answers

    What is the purpose of the diamond-shaped, yellow, pull-push control knob?

    <p>To apply and release the parking brake</p> Signup and view all the answers

    What is the benefit of a dual air brake system?

    <p>Improved safety</p> Signup and view all the answers

    What type of brake is used to meet the needs of emergency brakes and parking brakes?

    <p>Spring brake</p> Signup and view all the answers

    How do driveline brakes work?

    <p>They are operated by cables or levers</p> Signup and view all the answers

    What is the function of the rotor in a disc brake system?

    <p>To slow or stop the vehicle by squeezing the brake pads</p> Signup and view all the answers

    What happens when the air pressure in the air tanks falls below 60 psi?

    <p>The spring brakes engage automatically</p> Signup and view all the answers

    What is the purpose of the caliper in a disc brake system?

    <p>To squeeze the brake pads against the rotor</p> Signup and view all the answers

    What is the primary difference between drum brakes and disc brakes?

    <p>The location of the brake shoes and linings</p> Signup and view all the answers

    What causes friction in a drum brake system?

    <p>The brake shoes and linings pushing against the drum</p> Signup and view all the answers

    What is the purpose of the brake shoes and linings in a drum brake system?

    <p>To push against the inside of the drum to slow the vehicle</p> Signup and view all the answers

    What happens when the brake pedal is depressed in a disc brake system?

    <p>The caliper squeezes the brake pads against the rotor</p> Signup and view all the answers

    What is the primary function of the parking brake system?

    <p>To hold the vehicle stationary on an incline</p> Signup and view all the answers

    What is the primary function of the air compressor governor?

    <p>To automatically engage and disengage the compressor to maintain preset levels in the air storage tanks</p> Signup and view all the answers

    What is the result of condensation in the air storage tanks?

    <p>The creation of pools of water in the bottom of the air tanks</p> Signup and view all the answers

    What is the purpose of the air storage tanks?

    <p>To hold the compressed air for the service brake system</p> Signup and view all the answers

    What is the effect of moisture in the air storage tanks?

    <p>It can lead to blockages or malfunctions if the water freezes</p> Signup and view all the answers

    How is the air compressor powered?

    <p>Through gears or a V-line belt from the vehicle motor</p> Signup and view all the answers

    What determines the number and size of the air storage tanks?

    <p>The size of the vehicle and any auxiliary functions that draw air from the system</p> Signup and view all the answers

    What happens to the air as it is compressed?

    <p>It gets hotter</p> Signup and view all the answers

    What is the purpose of the air compressor in the air brake system?

    <p>To pump air into the air storage tanks</p> Signup and view all the answers

    What is the primary function of the S-cam in an S-cam brake system?

    <p>To push the brake shoes away from each other and press them against the brake drum</p> Signup and view all the answers

    What type of brake system uses a power screw to clamp the disc or rotor between the brake lining pads of a caliper?

    <p>Disc brake system</p> Signup and view all the answers

    What is the purpose of the supply pressure gauge in an air-brake vehicle?

    <p>To measure the air pressure in the air tank</p> Signup and view all the answers

    What happens when the S-cam rotates back in an S-cam brake system?

    <p>The brake shoes move away from the brake drum</p> Signup and view all the answers

    What type of brake system uses a wedge to push the brake shoes apart and against the inside of the brake drum?

    <p>Wedge brake system</p> Signup and view all the answers

    What is the purpose of the low air pressure warning signal in an air-brake vehicle?

    <p>To indicate when the air pressure in the air tank is too low</p> Signup and view all the answers

    What is the primary function of the brake camshaft in an S-cam brake system?

    <p>To rotate the S-cam</p> Signup and view all the answers

    What type of brake system is typically used in emergency vehicles?

    <p>S-cam brake system</p> Signup and view all the answers

    Study Notes

    Exhaust Systems

    • Diesel engines since 2007 are equipped with "aftertreatment" systems, which include Diesel Exhaust Fluid (DEF) and Diesel Particulate Filter (DPF).
    • DEF is a non-hazardous solution of 32.5% urea and 67.5% de-ionized water used to break down nitrogen oxide emissions.
    • DEF is stored in a separate tank, typically with a blue filler cap, and should be refilled when it reaches half.
    • Do not allow the DEF tank to reach empty, as the vehicle will automatically reduce power.
    • DEF crystallizes when stored for prolonged periods and should not be used in that state.

    Diesel Particulate Filter (DPF)

    • DPF indicator illuminates when sufficient particulate has accumulated in the system, requiring regeneration.
    • Regeneration occurs in two modes: automatically when the vehicle is at highway speeds for over 20 minutes or while parked.

    Exhaust System

    • The exhaust system is basic and consists of mufflers, exhaust pipes, tail pipes, and/or vertical stacks.
    • A faulty exhaust system can affect motor performance and emit poisonous fumes into the crew area, causing serious illness.

    Driveline

    • The driveline consists of the transmission, front universal joint, driveshaft, rear universal joint, differential, and rear axle.
    • The transmission is a system of gears that allows changes in the ratio of engine revolutions to wheel revolutions.

    Automatic Traction Control

    • Automatic traction control function aids tires in maintaining traction by monitoring wheel speeds and applying braking to a drive wheel that is spinning.
    • In extreme situations, engine speed may also be decreased until traction is achieved.

    Emergency Vehicle Pre-Response Preventive Inspections

    • Emergency vehicles should be inspected prior to each shift and after an event or incident that may cause damage to the vehicle.
    • The driver is responsible for confirming the vehicle is ready for use, and it is their responsibility to ensure mechanical safety.
    • Preventive maintenance inspections identify problems and permit temporary repairs.
    • Inspections, maintenance, and repairs must be recorded by the Department, including dates and descriptions of work performed.
    • Inspections can be broken into nine core areas: prior maintenance records, vehicle overview, engine compartment check, interior cab check, vehicle walk around check, compartment and equipment check, undercarriage check, and more.

    Braking and Stopping

    • Effective braking is crucial for safe operation of an emergency vehicle, requiring timely and controlled application of brakes to maintain control.
    • Prior to anti-lock braking systems (ABS), hydraulic brakes required pumping the brake pedal to avoid wheel lock, while air brakes required steady pressure to slow down without locking wheels.
    • With ABS, do not pump the brake pedal, as it confuses the monitoring system; instead, apply steady pressure to signal the system to slow down.
    • Even with ABS, vehicles can skid; if wheels lock, release the brake pedal and steer with the skid, then reapply the brakes to establish traction.
    • In high-probability braking areas, "cover" the brake by hovering the foot over the pedal without applying pressure to reduce reaction time.

    Safe Braking Techniques

    • Allow enough space around the vehicle to identify the need to brake and apply brakes in a controlled manner.
    • In heavy apparatus, expand the look-ahead distance to slow down using natural friction of the engine and compression.
    • In curves, coast at speed to maintain traction and avoid accelerating, which can cause loss of control.

    Exiting Curves

    • Maintain speed and position on the inner surface of the curve.
    • Gently accelerate out of the curve after the apex is reached and the vehicle is on a straight path.

    High-Speed Braking

    • Stopping at higher speeds requires more stopping distance and is harder on braking systems.
    • Braking creates friction, which can cause overheating and reduce braking effectiveness.
    • Reduce stress on brake systems by engaging auxiliary braking systems and downshifting the transmission.
    • Drum brakes fade more quickly than disc brakes due to differences in heat dissipation capability.

    Handling Unusual and Dangerous Driving Situations

    • Emergency vehicle operators must adjust driving techniques for adverse conditions, including traction implications, environmental hazards, and vision implications.

    Air Brake Systems

    • A warning signal must come on before air pressure in the air tanks falls below 60 psi.
    • The brake light switch warns drivers behind the vehicle when the brakes are applied.
    • Spring brakes are used to meet emergency brake and parking brake requirements.
    • Parking brake controls are typically operated using a diamond-shaped, yellow, pull-push control knob.

    Parking Brake Controls

    • Avoid pushing the brake pedal down when the spring brakes are on to prevent damage.
    • Apparatus equipped with air brakes use driveline brakes or spring-activated brakes as parking brakes.
    • Dual air brake systems are used for safety reasons in most new vehicles.

    Braking Systems

    • A vehicle's braking system converts inputs from the brake pedal or parking brake controls to the friction devices (brakes) located at each vehicle wheel.

    Types of Braking Systems

    • Hydraulic systems use liquid to create forces to engage friction devices.
    • Pneumatic (air) systems use compressed air to make brakes work.

    Drum Brakes

    • Have drums located on each end of the vehicle's axles.
    • Wheels are bolted to the drums and the braking mechanism is inside the drum.
    • Brake shoes and linings are pushed against the inside of the drum to slow the vehicle.

    Disc Brakes

    • Comprised of a rotor and a caliper that squeeze the brake pads to stop or slow the vehicle.
    • Rotor is the disc and is attached to the wheel axle.
    • Caliper squeezes brake pads against the rotor to slow or stop the vehicle.

    Pneumatic (Air) Brake Systems

    • Most commonly used in fire service apparatus and commercial motor vehicles.
    • Air brake system has three functions: service brake, parking brake, and emergency brake systems.

    Components of Air Brake System

    • Air Compressor: pumps air into air storage tanks, receives power from vehicle motor.
    • Air Compressor Governor: automatically engages and disengages compressor to maintain preset levels in air storage tanks.
    • Air Storage Tank: holds compressed air, number and size depend on vehicle size and auxiliary functions.

    Issues with Air Brake Systems

    • Water vapor in compressed air can lead to condensation and pools of water in air tanks.
    • Moisture can lead to blockages, malfunctions, corrosion, or reduce capacity in storage tanks.

    Types of Foundation Brake Systems

    • S-cam Brakes: air pressure pushes rod out, moving slack adjuster, twisting brake camshaft, forcing brake shoes against brake drum.
    • Wedge Brakes: brake chamber push rod pushes wedge directly between brake shoes, shoving them apart and against brake drum.
    • Disc Brakes: air pressure acts on brake chamber and slack adjuster, turning power screw, clamping disc or rotor between brake lining pads of a caliper.

    Other Components

    • Supply Pressure Gauge(s): shows pressure in air tank(s).
    • Low Air Pressure Warning: required on all vehicles with air brakes, signals low pressure.

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    Description

    This quiz covers the basics of vehicle exhaust systems, including aftertreatment systems and their impact on apparatus operation.

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