Heavy Duty Mechanics Practice Test

These questions are part of the practice quiz. Start practicing

• A fuel with a high Cetane number has which ignition property?
• Where is the intercooler typically located in a turbocharged engine?
• In a hydraulic circuit, what is the primary function of a load check valve?
• In a hydraulic circuit, what is the function of a pressure relief valve and a load check valve, and how do they differ?
• Which symptom is most indicative of a failing EGR valve?
• Which instrument is used to measure pressure and vacuum in engine systems?
• When starting fluid is being used it should be applied sparingly only:
• As the leaf spring deflects, the distance between the spring ends changes, and to permit this, one end of the spring is attached to the frame with:
• On a tandem truck, the right-hand rear tail light is dim. What is the most likely cause?
• An Hg. manometer is used to measure
• When replacing a hydraulic pump, how do you determine the correct rotation direction and why is it important?
• An excavator with a hydrostatic final drive uses a ______ for motive power.
• Which component in an alternator circuit is primarily responsible for rectification of AC to DC?
• In an alternator, the rotating magnetic field is produced by which component?
• How is air braking in heavy-duty trucks different from hydraulic braking, and what are typical components of an air brake system?
• What is the sequence to bleed a cooling system after a thermostat or radiator service?
• Which hydraulic component converts hydraulic flow and pressure to mechanical energy?
• A four-cycle engine requires ____ full turn(s) of the crankshaft to complete the combustion cycle.
• Which gauge is specifically known as a go-no-go gauge?
• What is the purpose of a fan clutch in a heavy-duty cooling system, and how does a failed fan clutch affect engine temperature?
• What is a no-start diagnostic path for a heavy-duty diesel engine (prioritizing safety), and what is the sequence to check common faults?
• Copper tubing is measured on the:
• What is the purpose of an air dryer in an air brake system?
• The difference between the amount of fuel-air mixture that actually enters the cylinder and the amount that could enter under ideal conditions is called:
• Which angle assists in maintaining the straight ahead position of the front wheels other than caster?
• In engine oil analysis, what does a milky oil most strongly indicate?
• Describe the typical maintenance interval considerations for hydraulic oil in heavy equipment, including contamination limits.
• If a seal lip is hardened and brittle with many cracks in the surface, _______ is probably the cause.
• In a hypoid gear set, the drive pinion is located relative to the center line of the ring gear.
• Positive caster corresponds to which description of the steering axis?
• Which practice best ensures cleanliness in hydraulic system maintenance?
• Ten psi of turbo boost corresponds to what absolute intake air pressure at sea level?
• If the wear line on the sprocket tooth is toward the top of the tooth (raised) the cause would be:
• Before extinguishing an electrical fire you should:
• Describe the function of a heavy-duty engine's oil pressure relief valve and what symptoms indicate it may be sticking.
• Which of the various types of hydraulic motors would provide the most torque?
• Before lifting with crane or lift equipment, which safety check is essential?
• Overwind operation of a winch refers to which practice?
• What is a likely consequence of an improper torque sequence when assembling a gasketed joint?
• The length of the drive line is allowed to change because of the
• In a hydrostatic final drive for an excavator, what provides the motive power?
• For general purpose drilling, which included angle is commonly ground on drill lips?
• The size of a shackle is determined by:
• A symptom that may indicate worn main bearings is:
• How does a diesel exhaust aftertreatment system (DEF) function with SCR, and what fault indicators show DEF dosing issues?
• Describe the procedure for performing a compression test on a heavy-duty diesel engine and interpreting results.
• On integral power steering, the control valve is located in the:
• Drive line angle must be correct in relation to
• A stepped feeler gauge is often called a:
• Tips of welding or cutting torches are cleaned with:
• Crankcase sludge forms most readily during which driving pattern?
• Generally speaking, as the size of a hose increases, its designated working pressure:
• What compression percentage is recommended for static O-ring seals?
• Which hydraulic component is primarily used to limit system pressure by routing excess flow back to the reservoir?
• Sixty-two and a half percent is equivalent to which fraction?
• How does a variable-geometry turbocharger (VGT) improve engine performance, and what issues can occur with vane positioning?
• Describe the steps to bleed air from a vehicle's hydraulic braking system after servicing.
• What is the purpose of a vacuum pump in a heavy-duty engine accessory drive and what are common failure signs?
• What overall pattern in an engine oil analysis would guide maintenance decisions?
• A simple method to check the operation of the shocks on a vehicle is to:
• When performing a basic electrical system diagnostic using a wiring diagram, which sequence best follows the recommended approach?
• Which three adjustable angles are found in a typical steering system?
• A clogged PCV valve or hose is likely to cause what condition in the engine?
• Dash number sizing of hydraulic hose refers to its inner diameter in:
• One of the most effective ways to stop a runaway diesel is to:
• What is the primary purpose of timing for a diesel engine's fuel injector, and how does timing deviation affect performance?
• To determine bolt head size for wrench selection, measure across which feature?
• For smooth clutch engagement, the clutch disc design incorporates
• What safety steps must you perform before servicing a powered hydraulic system?
• Which core solder is used for electrical connections?
• Which hydraulic component is primarily responsible for generating flow and pressure in the system?
• What are the two main diesel fuel filtration stages and their purposes?
• Cavitation erosion is caused by what phenomenon?
• A carburetor works on the basic principle of
• The length of the drive line is allowed to change because of the
• In a heavy-duty diesel engine cooling system, what is the function of the thermostat, and how does a faulty thermostat affect engine temperature?
• If the hydraulic pump becomes worn, which of the following is the likely effect on system performance?
• The radiator cap function in terms of boiling point is to
• Plastigauge is used to measure oil clearance by compressing between which surfaces?
• When soldering electrical connections, which core solder is used?
• Maximum swash plate angle on an inline axial piston motor would provide which combination?
• Which hydraulic component stores hydraulic energy for later use?
• What is a glow plug and when is it used in diesel engines?
• Define a torque-to-yield fastener and why improper torque can cause joint failure in heavy equipment.
• When caster adjustment is required on a solid axle, how is it achieved?
• Glow plugs in a diesel engine are used to?
• A bearing noise that occurs only when the clutch pedal is depressed comes from the
• Which angle helps keep the front wheels aligned straight ahead in addition to caster?
• A fuel with a high Cetane number is best described as having which ignition behavior?
• How should you read a digital multimeter when diagnosing an alternator charging system?
• When diagnosing wheel speed sensor faults in an ABS-equipped heavy vehicle, which diagnostic step is most appropriate?
• Which symptom most strongly indicates the wheel-end bearing is overheating?
• A headlight relay is an example of which type of device?
• When parking a piece of machinery, set the parking brakes then safely:
• A Caterpillar style steering clutch is usually:
• Which statements about coolant boiling point are true?
• Explain the role of common rail pressure in modern diesel engines and typical symptoms of a defective high-pressure fuel pump.
• What is a common effect of a CAN bus fault in a heavy-duty vehicle?
• Dump truck boxes should be blocked in the raised position because:
• Which condition would indicate a water pump failure?
• A tapered roller bearing is suited for:
• What is the purpose of a torque sequence and why must fasteners be torqued in a specific order?
• In heavy equipment, why is hydraulic fluid cleanliness critical, and how is it measured?
• What is the purpose of a diesel exhaust aftertreatment system, and name two common components.
• During coupling, which arrangement best describes the fifth wheel ramps orientation for proper alignment?
• Which combination identifies acetylene hose connections?
• A diode is designed to
• A diesel engine cooling system experiences overheating despite a functioning radiator fan. Which thermostat condition could explain this?
• Which action is NOT an effective way to stop a runaway diesel engine?
• When selecting suitable engine oil, one must consider viscosity and:
• Water would be satisfactory extinguishing a fuel oil fire.
• In a vehicle with air brakes, what is the purpose of an S-cam or wedge in drum brakes, and what maintenance checks are critical?
• Which sequence correctly describes replacing a hydraulic filter and explains why bypassing is dangerous?
• The best method of determining oil clearance in engine bearings is:
• What is the decimal equivalent of 3/8 inch?
• Which component is used to align the centre spring leaves to themselves and the axle?
• Describe spring brakes in air brake systems and when they engage.
• Which statement correctly differentiates copper tubing and pipe measurements?
• The headlight relay is best described as which component?
• The alternator magnetic field used to control the output is developed in the
• The term used for the length of time a fuel injector is energized is called
• A good diode will allow current to flow in
• A pyrometer is used:
• What is the primary purpose of an intercooler on a turbocharged engine?
• In a hydraulic circuit, the primary function of a pressure relief valve is to
• Positive caster is the:
• An accumulator may be used to:
• Before disconnecting any part of a hydraulic system, you should first:
• Which set of steps is essential for load testing and safety checks before lifting with crane or lift equipment?
• The inner diameter of a hydraulic hose is indicated by its dash number. If the dash number is 16, the inner diameter is approximately:
• The size of a shackle is determined by which dimension?
• Which symptom indicates that using an incorrect hydraulic fluid may cause valve operation issues?
• Most commercial alternators are
• How does fuel injector leak-down affect engine performance, and what test confirms leaks?
• The mechanism in a transmission that prevents shifting into two gears simultaneously is the
• Which option best describes overwind operation of a winch?
• Explain the purpose of a lubrication oil viscosity grade (e.g., 15W-40) and how ambient temperature influences selection.
• API service classification is used to evaluate engine oil suitability.
• The cooling system water pump primarily does what?
• What is the primary function of the ABS on a heavy-duty vehicle, and how is a wheel speed sensor fault commonly diagnosed?
• How should lubrication intervals be determined using oil analysis data and service history?
• In an air brake system, what component stores compressed air at high pressure?
• Which component allows the leaf spring end to extend as the spring deflects?
• Pipe is measured on the:
• How should lubrication intervals be determined using oil analysis data and service history?
• Frame alignment can be checked by:
• What are the consequences of using an incorrect hydraulic fluid in a heavy-duty system?
• The pre-cleaner operates primarily on which principle?
• What is the function of a crankcase ventilation (PCV) system and how can it fail to cause oil consumption issues?
• Two common oil pump types used in engines are rotor and gear.
• To allow for a longer period of ignition coil saturation, what adjustment is made to the dwell angle?
• What is the fractional equivalent of 0.625 inch?
• Describe the function of a service valve in an air brake system.
• When coupling a tractor to a trailer, the fifth wheel ramps should be oriented how for proper alignment?
• For a fully charged 12-volt lead-acid battery at room temperature, the typical open-circuit voltage is closest to which range?
• In electrical systems, what are the typical voltage levels and the function of a thermistor in an engine sensor circuit?
• Which instrument is used to set or measure the dwell angle in an ignition system?
• If an oil sample is to be taken during an oil change the oil should be collected
• Overwind operation of a winch is defined as...
• The length of time that an injector is energized is called
• What distinguishes cold-start techniques from hot-start techniques for diesel engines in cold weather?
• In diesel engines, how does a hot-start technique influence emissions compared with a cold-start?
• What is the function of the power steering system in heavy equipment?
• Which set correctly lists the three adjustable angles in a typical steering system?
• What is the purpose of a differential in a vehicle?
• Chain sizes are measured by:
• What is the basic function of a PTO (power take-off) in heavy-duty equipment?
• Which method cleans welding torch tips?
• When testing a fully charged battery between 15.5°C and 37.7°C, the open-circuit voltage should be within which range?
• Which component in the diesel exhaust aftertreatment system is primarily used to oxidize carbon monoxide and hydrocarbons?
• Worn main bearings may be indicated by:
• In engine oil analysis, which indicators suggest bearing wear or contamination?
• In automotive electrical systems, parallel circuits have which characteristics?
• When checking the main bearing oil clearance with plastigauge:
• Which of the following describes acetylene hose connections' thread and nut configuration?
• When removing a Pitman arm from the sector shaft, which method is recommended?
• What on-site testing method is commonly used to quantify hydraulic fluid cleanliness?
• What is the primary function of the radiator pressure cap?
• Drive shaft run out is checked with a
• For correct coupling of a tractor to a trailer, which position should the fifth wheel ramps have?
• An accumulator stores hydraulic pressure.
• In acetylene hose fittings, which configuration describes the connection?
• What is the purpose of a diesel particulate filter (DPF) and what regeneration types exist?
• When a wheel has positive camber the wheel is:
• What are the signs of a failing fuel lift pump in a diesel engine?
• What is the included angle commonly ground on drill lips for general purpose work?
• When determining the wrench size of a bolt, which distance is measured?
• What are the main functions of the exhaust gas recirculation (EGR) system, and common failure symptoms?
• A two-cycle engine requires ____ full turn(s) of the crankshaft to complete the combustion process.
• In injection timing, which statement is true about altering timing away from the specification?
• When removing a Pitman arm, what is the recommended method?
• Pressure relief valves allow oil to flow:
• Crankcase sludge forms more apt to form during
• What gas is used in hydro-air suspension or accumulators?
• Which of the following describes the acetylene hose connection identification?
• The first thing to check when a customer complains of 'lack of power assist' is:
• What is top-dead-center (TDC) and bottom-dead-center (BDC) in relation to engine timing, and how do they relate to injection timing?
• An incorrect camber on a vehicle with a solid I-beam front axle could be caused by which of the following?
• An "O" ring seal when used as a static seal should compress:
• What term describes the mechanism that prevents shifting into two gears at the same time in a manual transmission?
• What is a characteristic of gasoline with a higher octane rating?
• During a cylinder leak-down test, what is the correct method for confirming leaks?
• In winch operation, overwind refers to the line being wound in on top of the drum or under the drum?
• Which statement correctly describes the fifth wheel ramps during tractor-trailer coupling?
• The purpose of the bypass in an engine cooling system is to:
• The bypass in the engine cooling system serves to:
• The stroke of an engine is ____ the crank throw.
• What is the primary purpose of leaf spring center bolts?
• Two common types of oil pumps used in engines are:
• During plastigauge measurement on a main bearing, which action should be avoided?
• Acetylene hose connections are identified by which thread and nut combination?
• If the oil filter element becomes so clogged that all the oil needed by the engine cannot pass through the filter, which occurs?
• When a dump truck box is raised, blocking it is necessary to prevent which risk?
• Why is anti-freeze/coolant anti-corrosion important, and what happens if coolant is not maintained?
• What is the typical function of a wheel-end bearing, and which symptom suggests failure?
• What is the primary difference between a mechanical fuel pump and an electronic unit injector (EUI) system?
• When setting up a steering gear, which two adjustments must be made in the proper order?
• In an inline axial piston motor, the maximum swash plate angle yields which combination of speed and torque?
• Progressive rate springs are:
• Which statement accurately reflects acetylene hose connection identification?
• In the proper order for steering gear adjustments, which adjustment should be performed first?
• During a compression test, what does a significantly lower reading on one cylinder relative to others typically indicate?
• What is CAN bus and how is it used in heavy-duty vehicle electronic systems?
• What is the function of the radiator cap in the cooling system, and what could happen if the cap is not sealing properly?