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SKM Motor Vehicle Mechanic Level 3 study materials
SKM Motor Vehicle Mechanic Level 3 study resources

SKM Motor Vehicle Mechanic Level 3 practice questions

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Question 1Occupational Safety and Health (OSHA) and Environmental Compliance

A mechanic is about to arc weld a vehicle frame in a service bay. Under typical OSHA general industry requirements, which control must be in place before welding begins?

  1. A minimum of two coworkers standing by with water hoses
  2. A written permit signed by the shop owner for every weld bead
  3. Local exhaust ventilation or other effective fume control plus eye and skin protection Correct answer.
  4. The bay doors fully closed to keep the shielding gas contained

Explanation

Welding produces metal fume, ozone, and intense ultraviolet and infrared radiation, so OSHA requires effective ventilation to keep exposure below permissible limits and appropriate eye and skin protection. Closing the bay traps contaminants and raises exposure, and no rule demands a signed permit per bead or water-hose attendants.

Question 2Occupational Safety and Health (OSHA) and Environmental Compliance

Which document must be available in the shop and explain the hazards, safe handling, and emergency measures for the brake cleaner and solvents stored there?

  1. The shop's business insurance certificate
  2. The vehicle manufacturer's warranty booklet
  3. The local fire department inspection report
  4. The Safety Data Sheet for each hazardous chemical Correct answer.

Explanation

OSHA's Hazard Communication standard requires employers to keep a Safety Data Sheet for every hazardous chemical in the workplace and make it accessible to workers. The SDS covers hazard identification, handling precautions, and first-aid and spill response.

Question 3Occupational Safety and Health (OSHA) and Environmental Compliance

A used oil drum in the shop is labeled with the shop's name and the words 'Used Oil.' Under used oil management rules, which additional practice is required?

  1. Storing the drum on bare soil so leaks drain away
  2. Keeping the container closed except when adding or removing oil Correct answer.
  3. Mixing the used oil with spent chlorinated solvent to save space
  4. Transferring the oil to an unmarked tank before pickup

Explanation

Used oil containers must be labeled and kept closed except when oil is being added or removed, which prevents spills and vapor release. Storing on bare soil risks contamination, mixing with solvent can make the oil hazardous waste, and unmarked tanks defeat labeling requirements.

Question 4Occupational Safety and Health (OSHA) and Environmental Compliance

A technician must drain and replace the refrigerant in an air-conditioning system. Which certification is required before performing this service?

  1. A commercial driver's license with hazmat endorsement
  2. A state electrical journeyman license
  3. An OSHA 30-hour general industry card
  4. Section 609 certification for motor vehicle refrigerant handling Correct answer.

Explanation

Under the Clean Air Act refrigerant rules, technicians who service motor vehicle air-conditioning systems must hold Section 609 certification for proper refrigerant recovery and handling. The other credentials address electrical work, general safety training, or driving, not refrigerant service.

Question 5Occupational Safety and Health (OSHA) and Environmental Compliance

A vehicle on a two-post lift must be raised so the mechanic can work underneath. Which practice best controls the crushing hazard?

  1. Placing a floor jack under the axle as a backup while the lift is up
  2. Setting the lift's mechanical locks and checking the vehicle is stable before going under Correct answer.
  3. Leaving the lift on hydraulic pressure only, with the locks disengaged
  4. Raising the vehicle while a coworker holds the frame steady by hand

Explanation

Lifts must be lowered onto their mechanical safeties so a hydraulic failure cannot drop the load, and the vehicle should be checked for stability before anyone works beneath it. Relying on hydraulic pressure alone or on a person holding the vehicle leaves the crushing hazard uncontrolled.

Question 6Occupational Safety and Health (OSHA) and Environmental Compliance

When compressed air is used to clean parts or the workbench, OSHA limits the dead-end pressure at the nozzle to which maximum?

  1. 90 psi
  2. 60 psi
  3. 30 psi Correct answer.
  4. 120 psi

Explanation

OSHA limits compressed air used for cleaning to 30 psi dead-end pressure, and the nozzle must have relief protection so pressure cannot build if the outlet is blocked. Higher pressures can drive debris or air into the skin and cause serious injury.

Question 7Occupational Safety and Health (OSHA) and Environmental Compliance

A mechanic will spray refinish paint containing isocyanates in a booth. Which combination best meets respiratory protection requirements?

  1. A dust mask worn over a beard for a tight seal
  2. A single disposable N95 mask reused until it looks dirty
  3. A supplied-air respirator or an appropriate cartridge respirator selected through a written program with fit testing Correct answer.
  4. No respirator, provided the booth door is left open

Explanation

Isocyanate paints require a respirator chosen under a written respiratory protection program that includes medical evaluation, fit testing, and training, often supplied-air in a booth. Facial hair breaks the seal, and N95 masks do not filter isocyanate vapors.

Question 8Occupational Safety and Health (OSHA) and Environmental Compliance

A drum of solvent in the shop has no label and the container's contents are unknown. What is the correct action under hazard communication rules?

  1. Pour it into the used oil tank to avoid waste fees
  2. Smell the liquid to identify it before use
  3. Treat it as unknown hazardous material and label or dispose of it through proper channels Correct answer.
  4. Assume it is water and dispose of it in the drain

Explanation

Unlabeled containers must not be used, and unknown material should be treated as hazardous until identified by proper means. Smelling chemicals is dangerous, and dumping unknown liquid into a drain or the used oil tank can create regulated waste and contamination.

Question 9Occupational Safety and Health (OSHA) and Environmental Compliance

A shop generates spent parts-washer solvent that is a listed hazardous waste. Which accumulation requirement applies to the closed container while it waits for pickup?

  1. It must be diluted with water to reduce its concentration
  2. It must be stored outdoors on the parking lot
  3. It may be stored indefinitely as long as it is capped
  4. It must be labeled with accumulation start date and hazard, and removed within the applicable time limit Correct answer.

Explanation

Hazardous waste containers at a generator site must be labeled with the accumulation start date and contents, kept closed, and shipped off site within the allowed accumulation time. Indefinite storage, outdoor dumping, and dilution are not compliant management methods.

Question 10Occupational Safety and Health (OSHA) and Environmental Compliance

An engine is running in a bay with the overhead door closed during cold weather. Which hazard is the primary concern and what control is appropriate?

  1. Ozone buildup; install an ozone generator
  2. Dust accumulation; wear a dust mask
  3. Carbon monoxide buildup; route exhaust to the outdoors or open ventilation Correct answer.
  4. Refrigerant leakage; add more refrigerant

Explanation

Engine exhaust contains carbon monoxide, an odorless gas that can reach dangerous levels in an enclosed bay. Exhaust hoses vented outdoors or adequate mechanical ventilation keep CO below harmful concentrations; ozone generators and dust masks do not address it.

Question 11Occupational Safety and Health (OSHA) and Environmental Compliance

A mechanic finds a small puddle of antifreeze on the shop floor. Which response best reflects spill control and environmental practice?

  1. Absorb it, collect the material for proper disposal, and clean the area Correct answer.
  2. Hose it into the floor drain so it does not stain the concrete
  3. Leave it to evaporate overnight
  4. Cover it with cardboard and continue working

Explanation

Antifreeze contains ethylene glycol, which is toxic to people and animals and must not enter drains or storm sewers. Absorbing the spill, containerizing the residue for proper disposal, and cleaning the floor prevents environmental release and slip hazards.

Question 12Occupational Safety and Health (OSHA) and Environmental Compliance

A battery is being charged in the shop. Which practice best controls the associated chemical and fire hazards?

  1. Charging in a closed cabinet to keep sparks contained
  2. Charging in a ventilated area away from ignition sources with eye protection available Correct answer.
  3. Adding tap water to the cells while the charger is on
  4. Smoking is permitted if the battery caps are tight

Explanation

Lead-acid charging releases hydrogen gas, which is flammable, and electrolyte is corrosive, so ventilation, ignition control, and eye protection are needed. Sealed cabinets can trap hydrogen, and open flames near a charging battery risk explosion.

Question 13Occupational Safety and Health (OSHA) and Environmental Compliance

A grinder used for sharpening parts is missing its tongue guard and the work rest is set far from the wheel. What is the correct interpretation?

  1. The grinder is acceptable if the operator wears safety glasses
  2. The work rest can be removed entirely for better access
  3. The grinder must be taken out of service until the guards are adjusted to required distances Correct answer.
  4. The grinder may be used for light work only

Explanation

OSHA requires grinder tongue guards and work rests to be adjusted to specified maximum gaps from the wheel to prevent parts being pulled in and sparks flying. Missing or misadjusted guards are a defect that requires removing the machine from service, not a workaround.

Question 14Occupational Safety and Health (OSHA) and Environmental Compliance

A shop stores oxygen and acetylene cylinders for torch work. Which storage arrangement meets typical OSHA requirements?

  1. Oxygen and acetylene cylinders chained together upright against the same wall
  2. All cylinders laid horizontally on the floor to prevent tipping
  3. Oxygen and acetylene cylinders separated by at least 20 feet or a noncombustible barrier at least 5 feet high Correct answer.
  4. Acetylene cylinders stored in a closed metal cabinet with the valve caps removed

Explanation

Fuel gas and oxygen cylinders must be kept apart by at least 20 feet or a noncombustible barrier at least 5 feet high, and cylinders must be secured upright with valve protection in place. Storing them together or laying them down increases fire and explosion risk.

Question 15Occupational Safety and Health (OSHA) and Environmental Compliance

A technician is about to work under a vehicle supported only by a hydraulic floor jack. What is the correct safety judgment?

  1. The jack is sufficient if the vehicle is on level concrete
  2. The jack may be used alone if the work takes less than a minute
  3. A wheel chock under one tire replaces the need for stands
  4. Jack stands must be placed under the vehicle before any part of the body goes underneath Correct answer.

Explanation

A hydraulic jack is a lifting device, not a support device, so jack stands must carry the load before anyone works beneath a vehicle. Level ground and chocks reduce rolling but do not protect against a jack losing pressure or tipping.

Question 16Occupational Safety and Health (OSHA) and Environmental Compliance

A shop wants to reduce the volume of hazardous waste it generates from parts cleaning. Which approach best follows the waste management hierarchy?

  1. Buy more solvent in bulk so fewer containers are used
  2. Switch to an aqueous or low-VOC parts washer to reduce hazardous solvent use Correct answer.
  3. Store spent solvent longer to let solids settle and then pour off the liquid
  4. Burn the spent solvent in a shop heater

Explanation

Source reduction is the preferred tier of the waste hierarchy, so substituting a less hazardous cleaning method reduces waste at the source. Buying more solvent, burning it on site, or decanting it does not reduce the hazardous waste generated and may violate rules.

Question 17Occupational Safety and Health (OSHA) and Environmental Compliance

A worker is exposed to noise from air tools measured at 92 dBA over an 8-hour shift. What does OSHA require in this situation?

  1. Rotation of workers so each is exposed for four hours only
  2. A hearing conservation program including monitoring, audiometric testing, and hearing protection Correct answer.
  3. Only a warning sign posted at the bay entrance
  4. No action, because the level is below 100 dBA

Explanation

OSHA's hearing conservation program is triggered at an 8-hour time-weighted average of 85 dBA, so 92 dBA requires monitoring, audiometric testing, hearing protection, and training. Signs alone or informal rotation do not satisfy the program requirements.

Question 18Occupational Safety and Health (OSHA) and Environmental Compliance

A shop handles a spill of a corrosive battery electrolyte on a worker's arm. Which immediate response is correct?

  1. Flush the affected skin with copious water at an eyewash or shower for at least 15 minutes and seek medical attention Correct answer.
  2. Neutralize the acid with a strong base before rinsing
  3. Apply an ointment and cover the area with a bandage
  4. Wipe the area dry with shop rags and continue working

Explanation

Corrosive electrolyte exposure requires immediate and prolonged flushing with water, typically for at least 15 minutes, followed by medical evaluation. Neutralizing chemicals can cause additional thermal or chemical injury and should not be applied to skin.

Question 19Occupational Safety and Health (OSHA) and Environmental Compliance

A shop's air compressor receiver has a pressure gauge but no relief valve and the drain is never opened. Which combination of concerns is most accurate?

  1. The drain should be welded shut to prevent air loss
  2. The gauge alone provides adequate overpressure protection
  3. Overpressure protection is missing and condensate accumulation can corrode the tank, so both must be corrected Correct answer.
  4. Only noise is a concern, since the tank is rated for high pressure

Explanation

Air receivers require a pressure relief device to prevent overpressure and regular draining to remove condensate that corrodes the tank from inside. A gauge only indicates pressure and cannot relieve it, and sealing the drain accelerates corrosion.

Question 20Occupational Safety and Health (OSHA) and Environmental Compliance

A shop plans to dispose of used oil filters and oily shop rags. Which approach best reflects proper waste handling?

  1. Place them in the regular trash after squeezing out the oil
  2. Burn them in an open pit to reduce volume
  3. Bury them behind the shop to avoid disposal costs
  4. Drain the filters, manage the oil and filter residues through proper recycling or disposal channels, and keep rags in a closed marked container Correct answer.

Explanation

Used oil filters and solvent- or oil-soaked rags can carry regulated contaminants, so they must be drained, containerized, and routed through appropriate recycling or disposal. Trash disposal, burying, and open burning can violate waste rules and pollute the environment.

Question 21Workshop Practice, Tools, and Equipment

When torqueing a cylinder head to a specified final figure using a calibrated click-type torque wrench, what is the correct workshop procedure?

  1. Apply the final torque in one continuous pull from zero to the set value
  2. Set the wrench above the target and loosen to the click point
  3. Tighten in the specified sequence in stages, finishing with the final figure Correct answer.
  4. Oil the threads and reduce the setting by ten percent to allow for friction

Explanation

Cylinder heads must be tightened in the manufacturer's sequence and in progressive stages so the gasket compresses evenly and the head does not distort. The final pass brings each fastener to the specified figure. A single pull from zero risks uneven clamping and gasket damage.

Question 22Workshop Practice, Tools, and Equipment

A metric micrometer reading shows 7.5 mm on the sleeve and the thimble line coinciding with the 22nd division. If the thimble has 50 divisions, what is the measured dimension?

  1. 7.72 mm Correct answer.
  2. 7.44 mm
  3. 7.22 mm
  4. 7.50 mm

Explanation

Each thimble division on a 0.5 mm-pitch micrometer equals 0.01 mm, so 22 divisions add 0.22 mm to the sleeve reading. Adding this to 7.50 mm gives 7.72 mm. Reading the sleeve and thimble separately before summing avoids the common error of misplacing the decimal.

Question 23Workshop Practice, Tools, and Equipment

Why is a Plastigauge strip used when checking bearing clearance during assembly?

  1. It shows the crush height of the bearing shell
  2. It measures the oil pressure the bearing will sustain
  3. It indicates clearance by its flattened width after tightening Correct answer.
  4. It records the maximum temperature reached during running-in

Explanation

A Plastigauge strip is placed across the journal and the cap is torqued to specification; the strip flattens in proportion to the gap. Comparing the flattened width with the printed scale gives the bearing clearance without dismantling measuring equipment. The strip is removed and replaced with lubricant before final assembly.

Question 24Workshop Practice, Tools, and Equipment

A four-post vehicle lift is being used for a routine underbody inspection. Which practice best protects the technician and the vehicle?

  1. Leave the lift on the hydraulic circuit alone with no mechanical locks engaged
  2. Raise the vehicle fully before checking that the wheels sit squarely on the runways
  3. Stand beneath the raised vehicle while an assistant operates the controls
  4. Confirm the vehicle is centred, the runways clear, and mechanical locks engaged before going under Correct answer.

Explanation

The vehicle must be positioned so its weight is distributed over the runways, with nothing obstructing the lift path, and the mechanical safety locks must be engaged before anyone works underneath. Hydraulic pressure alone is not a safe support. A pre-lift and mid-lift check is standard practice.

Question 25Workshop Practice, Tools, and Equipment

What is the primary purpose of using a torque-to-yield bolt on certain suspension and engine assemblies?

  1. To permit the fastener to be loosened with a standard screwdriver
  2. To reduce the required tightening torque to finger tightness
  3. To clamp the joint consistently by tightening beyond the elastic range into a controlled stretch Correct answer.
  4. To allow repeated reuse without measurement

Explanation

Torque-to-yield fasteners are tightened past their elastic limit so they stretch a controlled amount, producing a consistent clamp load that is more reliable than friction-based torque alone. Because they are permanently deformed, they are normally replaced rather than reused. This is why a torque-plus-angle procedure is specified.

Question 26Workshop Practice, Tools, and Equipment

During a compression test on a petrol engine, one cylinder reads significantly low. Adding a small amount of oil to that cylinder raises the reading to normal. What does this indicate?

  1. A jumped timing chain
  2. Worn piston rings or cylinder bore Correct answer.
  3. A leaking head gasket
  4. A burnt exhaust valve

Explanation

Oil temporarily seals the gap between the rings and the bore, so a reading that improves after oiling points to ring or bore wear. If the reading stays low, the leakage is more likely at the valves or head gasket. This wet-and-dry comparison is the standard diagnostic step.

Question 27Workshop Practice, Tools, and Equipment

Which instrument is the correct choice for measuring the outside diameter of a valve stem to check wear against specification?

  1. Outside micrometer with 0.01 mm graduations Correct answer.
  2. Dial test indicator on a magnetic base
  3. Feeler gauge set
  4. Vernier caliper with 0.02 mm graduations

Explanation

A valve stem requires a measurement resolution and accuracy better than the wear tolerance, and an outside micrometer with 0.01 mm graduations provides this. A vernier caliper is convenient but less precise and more prone to operator error on small diameters. Feeler gauges and dial indicators measure gaps and runout, not diameter.

Question 28Workshop Practice, Tools, and Equipment

A technician is about to remove a stubborn hub nut using a long breaker bar. Which combination of practices is most appropriate?

  1. Use a twelve-point socket to spread the load and strike the bar with a hammer
  2. Use an impact socket on a ratchet and apply steady pressure while standing on the bar
  3. Heat the nut to red heat and then apply force with an open-ended spanner
  4. Use a six-point socket of the correct size, pull rather than push, and use a cheater bar with care Correct answer.

Explanation

A correctly sized six-point socket grips the flats and reduces the risk of rounding the nut. Pulling toward the body gives better control if the fastener suddenly releases, and any extension bar must be used with awareness of the increased leverage and reduced socket strength.

Question 29Workshop Practice, Tools, and Equipment

What is the correct method for checking the calibration status of a workshop torque wrench before a precision assembly job?

  1. Loosen the adjustment to zero and assume it is accurate
  2. Set it to maximum and check that it clicks twice
  3. Ask another technician whether it feels right
  4. Compare it against a known test rig or reference beam at the working setting and record the result Correct answer.

Explanation

Calibration is verified by comparing the wrench output against a traceable reference at the torque value to be used, and the result should be recorded. This confirms the wrench is within its stated tolerance before critical fasteners are tightened. Wrenches are also stored at their lowest setting to protect the spring.

Question 30Workshop Practice, Tools, and Equipment

Which personal protective equipment is essential when using a pedestal grinder to sharpen a chisel?

  1. Leather gloves only, with the guard removed for access
  2. Face shield and safety glasses, with the tool rest set close to the wheel Correct answer.
  3. Ear defenders only, with the tool held freehand
  4. A dust mask only, with the wheel running at low speed

Explanation

Grinding throws sparks and fragments, so eye and face protection are essential, and the tool rest should be set close to the wheel to prevent the work being drawn in. The guard must remain fitted and the wheel should run at its rated speed. Gloves near rotating machinery create an entanglement hazard.

Question 31Workshop Practice, Tools, and Equipment

A dial bore gauge is zeroed against a micrometer set to the nominal bore size. When inserted into the cylinder, the needle moves 0.03 mm past zero on the plus side. What is the bore size relative to nominal?

  1. 0.30 mm larger than nominal
  2. Exactly nominal
  3. 0.03 mm smaller than nominal
  4. 0.03 mm larger than nominal Correct answer.

Explanation

The gauge is set so that zero corresponds to the nominal dimension, and movement to the plus side indicates a larger bore. The reading is therefore nominal plus 0.03 mm. This comparison method lets the technician read deviation directly rather than interpreting an absolute scale.

Question 32Workshop Practice, Tools, and Equipment

Why should a vehicle's electronic control unit be protected before electric arc welding is carried out on the body?

  1. To stop the welding machine from overcharging the battery
  2. To ensure the weld penetrates more deeply
  3. To prevent the welding current from damaging sensitive electronics through the vehicle's earth paths Correct answer.
  4. To keep the paint from blistering near the weld

Explanation

Arc welding current can travel through the vehicle's wiring and earth returns, inducing voltages that destroy sensitive electronic modules. Disconnecting the battery and clamping the welder earth close to the work reduces this risk. Manufacturers also specify additional precautions for some models.

Question 33Workshop Practice, Tools, and Equipment

A hydraulic trolley jack is used to raise a vehicle for a wheel removal. What must be done before the wheel is taken off?

  1. Place axle stands under the recommended jacking points and lower the vehicle onto them Correct answer.
  2. Leave the jack holding the load and work quickly
  3. Lower the jack slightly to settle the suspension
  4. Chock the diagonally opposite wheel and rely on the jack

Explanation

A jack is a lifting device, not a support device, so axle stands must be positioned under the manufacturer's recommended points and the vehicle lowered onto them before any work begins. Wheels should also be chocked where appropriate. This prevents the vehicle dropping if the jack seal fails.

Question 34Workshop Practice, Tools, and Equipment

Which condition would most likely cause a false high reading on a compression gauge during a routine engine test?

  1. An engine at normal operating temperature
  2. A fully charged battery and correct cranking speed
  3. A throttle plate held fully open during cranking
  4. Excess carbon build-up raising the compression ratio Correct answer.

Explanation

Carbon deposits reduce combustion chamber volume and can raise the measured compression above the specified figure, giving a misleadingly healthy result. Test conditions such as battery condition, engine temperature and throttle position must be consistent to allow comparison between cylinders.

Question 35Workshop Practice, Tools, and Equipment

A technician needs to remove a seized exhaust manifold stud from an aluminium cylinder head. Which approach best reduces the risk of damaging the head?

  1. Apply penetrating fluid, use a stud extractor with steady torque, and apply heat to the surrounding head material if needed Correct answer.
  2. Drill out the stud completely before attempting any other method
  3. Strike the stud repeatedly with a hammer to break the corrosion
  4. Use a large pipe wrench and apply maximum force immediately

Explanation

Aluminium heads are easily damaged, so a controlled approach is required: penetrating fluid, a proper stud extractor, and localised heat to expand the head around the stud. Steady torque avoids shearing the stud. Drilling is a last resort after other methods fail.

Question 36Workshop Practice, Tools, and Equipment

What is the correct interpretation of a runout reading of 0.08 mm on a brake disc measured with a dial test indicator?

  1. The disc face deviates by 0.08 mm from true rotation Correct answer.
  2. The disc has 0.08 mm of lateral play in its bearing
  3. The disc runout is within specification regardless of the limit
  4. The disc thickness is 0.08 mm below minimum

Explanation

Runout measures how far the disc face moves away from a true plane as it rotates, so 0.08 mm is the total indicated deviation. It is compared against the manufacturer's runout limit, not the thickness limit. Excessive runout can cause pedal pulsation.

Question 37Workshop Practice, Tools, and Equipment

Which storage practice best preserves the accuracy of precision measuring tools such as micrometers and vernier calipers?

  1. Store them with the measuring faces closed tightly against each other
  2. Store them loosely in a shared drawer with other hand tools
  3. Clean them, lightly oil the measuring faces, and store them in their cases away from moisture and shock Correct answer.
  4. Hang them by the thimble on a workshop hook

Explanation

Precision tools should be cleaned after use, given a light protective film, and kept in their cases to protect against corrosion, dirt and impact. Micrometer faces should be left slightly open rather than clamped shut, which can damage the measuring surfaces.

Question 38Workshop Practice, Tools, and Equipment

An engine is being reassembled and the specification gives a bolt torque of 40 Nm plus 90 degrees. What does the angle figure represent?

  1. A tolerance of plus or minus 90 degrees on the torque setting
  2. A waiting period before the final torque is applied
  3. An additional rotation applied after the initial torque to achieve the correct bolt stretch Correct answer.
  4. The angle at which the wrench must be held

Explanation

In a torque-plus-angle procedure the initial torque seats the fastener, and the specified rotation then stretches the bolt a controlled amount to produce the designed clamp load. The angle is measured with a protractor gauge or by counting flats. This method compensates for friction variation better than torque alone.

Question 39Workshop Practice, Tools, and Equipment

During a road test a technician hears a rhythmic clicking from a front wheel that changes with vehicle speed but not with engine speed. Which workshop check is the most direct first step?

  1. Inspect the CV joint boots and check for play in the joint Correct answer.
  2. Replace the engine mounts
  3. Check the exhaust heat shield for looseness
  4. Measure the alternator belt tension

Explanation

A speed-related rhythmic click from a wheel area commonly indicates a worn constant-velocity joint, especially if a boot is split and grease has been lost. Inspecting the boots and checking joint play is a quick, non-invasive first step. Engine-speed-related noises would point elsewhere.

Question 40Workshop Practice, Tools, and Equipment

Which of the following is the correct reason for using a thread pitch gauge when identifying an unfamiliar bolt?

  1. To check whether the bolt has been stretched
  2. To determine the bolt's tensile strength grade
  3. To match the thread form and pitch so the correct nut or tap can be selected Correct answer.
  4. To measure the length of the bolt under the head

Explanation

A thread pitch gauge consists of leaves with known thread forms that are offered up to the bolt until the profiles match, identifying the thread type and pitch. This ensures the correct replacement fastener or tap is chosen. Strength grade is marked on the head, and length is measured with a rule or caliper.

Question 41Engine Systems: Diagnosis, Service, and Repair

During a cylinder leakage test on a four-stroke petrol engine, air escapes continuously from the oil filler neck with the piston at TDC on the compression stroke. Which component is the most likely cause?

  1. A leaking inlet valve
  2. A cracked spark plug insulator
  3. Worn piston rings or a damaged piston Correct answer.
  4. A blown head gasket between adjacent cylinders

Explanation

Air entering the crankcase and exiting the oil filler indicates leakage past the piston rings, piston or cylinder bore because the combustion chamber is connected to the crankcase below the rings. A valve leak would show at the inlet or exhaust port instead.

Question 42Engine Systems: Diagnosis, Service, and Repair

Which instrument is used to measure the internal diameter of a cylinder bore accurately during an engine overhaul?

  1. Bore gauge (dial bore comparator) Correct answer.
  2. Feeler gauge
  3. Vernier caliper
  4. Outside micrometer

Explanation

A bore gauge is set against a micrometer and then read inside the bore, giving an accurate internal measurement including taper and ovality. An outside micrometer measures external dimensions and cannot reach inside the bore reliably.

Question 43Engine Systems: Diagnosis, Service, and Repair

A compression test on a petrol engine shows one cylinder reading about 30 percent below the others, but the reading rises to normal after a small amount of engine oil is added to the cylinder. What does this indicate?

  1. A faulty ignition coil
  2. A worn piston ring or bore Correct answer.
  3. A jumped timing chain
  4. A burnt exhaust valve

Explanation

Oil temporarily seals the gap between the rings and bore, so the wet reading improving to normal confirms ring or bore wear. A valve fault would not be sealed by oil and the reading would remain low.

Question 44Engine Systems: Diagnosis, Service, and Repair

Which of the following is the correct sequence when removing a cylinder head from an engine with a cast aluminium head?

  1. Remove the bolts starting at one end and work along the row
  2. Loosen bolts in the reverse of the tightening sequence, in stages, with the engine cold Correct answer.
  3. Loosen all bolts fully in any order while hot
  4. Remove the bolts from the centre outwards in one pass

Explanation

Head bolts must be released gradually in stages following the reverse of the specified tightening sequence, normally with the engine cold, to avoid warping the aluminium head. A single pass or end-to-end removal concentrates stress and distorts the casting.

Question 45Engine Systems: Diagnosis, Service, and Repair

A technician is checking valve clearances on an engine with mechanical lifters. The clearance on one exhaust valve is 0.15 mm when the specification is 0.30 mm. What is the most likely consequence if the engine is run in this condition?

  1. The valve will not close fully, causing a burnt valve Correct answer.
  2. The camshaft lobe will wear rapidly
  3. The valve will not open fully, reducing power
  4. The valve spring will break immediately

Explanation

Too small a clearance prevents the valve from seating fully when the engine is hot, so combustion gases escape past the valve face and can burn the valve. Correct clearance allows for thermal expansion of the valve stem.

Question 46Engine Systems: Diagnosis, Service, and Repair

Which component in a turbocharged petrol engine controls the boost pressure delivered to the intake manifold?

  1. Throttle position sensor
  2. Wastegate or boost control solenoid Correct answer.
  3. EGR valve
  4. Purge valve

Explanation

The wastegate, or the boost control solenoid acting on it, bypasses exhaust gas around the turbine to limit turbine speed and therefore boost pressure. This protects the engine from over-boost.

Question 47Engine Systems: Diagnosis, Service, and Repair

An engine has a persistent misfire on cylinder 3. A compression test is normal, the spark plug and coil are swapped with a known-good cylinder and the misfire stays on cylinder 3. What is the next logical diagnostic step?

  1. Check injector operation and perform a cylinder balance test Correct answer.
  2. Adjust the valve clearances
  3. Replace the ECU
  4. Replace all spark plugs

Explanation

With ignition components eliminated by substitution and compression confirmed good, the remaining variables are fuel delivery and mechanical valve action. Checking the injector and running a cylinder balance test isolates the cause efficiently.

Question 48Engine Systems: Diagnosis, Service, and Repair

What is the primary purpose of the cooling system thermostat in a liquid-cooled engine?

  1. To maintain coolant at the designed operating temperature by regulating flow Correct answer.
  2. To circulate coolant through the radiator
  3. To remove air from the cooling system
  4. To pressurise the cooling system

Explanation

The thermostat opens and closes to control coolant flow to the radiator, keeping the engine within its designed temperature range for efficiency and emissions. It does not circulate coolant or pressurise the system.

Question 49Engine Systems: Diagnosis, Service, and Repair

A pressure test on the cooling system shows a steady loss of pressure with no external leak visible. The oil level on the dipstick is rising and the oil looks milky. Which fault is most likely?

  1. A failed head gasket or cracked head Correct answer.
  2. A leaking water pump seal
  3. A faulty radiator cap
  4. A stuck-open thermostat

Explanation

Coolant entering the crankcase raises the oil level and produces a milky emulsion, pointing to a breach between the cooling jacket and oil galleries via the head gasket or a cracked casting. External leaks would be visible on the ground or components.

Question 50Engine Systems: Diagnosis, Service, and Repair

During a cylinder compression test on a diesel engine, what should be done before cranking to obtain valid readings?

  1. Open the throttle fully with the engine cold
  2. Warm the engine to operating temperature and disable the fuel supply Correct answer.
  3. Remove all glow plugs and leave the fuel system connected
  4. Add oil to every cylinder

Explanation

Diesel compression tests require a fully charged battery, a warm engine and the fuel supply disabled to prevent starting and to avoid washing oil from the bores. Removing the injectors or glow plugs provides the pressure tap.