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SKM Motor Vehicle Mechanic L2 study materials
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SKM Motor Vehicle Mechanic L2 practice questions

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Question 1Occupational Safety and Health in the Automotive Workshop

A mechanic must work underneath a vehicle that is raised on a two-post hoist. Which practice best protects the mechanic from a falling-load hazard?

  1. Lower the vehicle onto mechanical safety locks before going under it Correct answer.
  2. Keep the hoist control pendant within reach at all times
  3. Rely on the hydraulic system alone to hold the vehicle
  4. Place a jack stand under the sill as an extra support

Explanation

Hydraulic pressure can bleed off if a hose or seal fails, so the mechanical safety locks must be engaged to positively hold the arms. Only after the locks are engaged and the load is stable should anyone work beneath the raised vehicle.

Question 2Occupational Safety and Health in the Automotive Workshop

What is the main reason workshop compressed-air lines are fitted with a pressure regulator at the point of use?

  1. To increase airflow volume to the impact wrench
  2. To keep tool pressure at the manufacturer's rated value Correct answer.
  3. To lubricate the internal parts of air tools
  4. To remove water vapour from the air supply

Explanation

Air tools are rated for a specific working pressure, and excess pressure accelerates wear and increases the severity of a hose or coupling failure. A regulator at the point of use holds the delivered pressure at the tool's rated value regardless of line fluctuations.

Question 3Occupational Safety and Health in the Automotive Workshop

A vehicle is being run inside the workshop with the engine idling for diagnosis. What is the correct control for exhaust emissions?

  1. Open the main workshop door and rely on natural draught
  2. Connect an extraction hose to the tailpipe and run it outdoors Correct answer.
  3. Direct a pedestal fan at the tailpipe to disperse the fumes
  4. Run the engine for no more than five minutes at a time

Explanation

Carbon monoxide in exhaust is odourless and can build to dangerous levels even with doors open, so the exhaust must be captured at the tailpipe and ducted outside. A tailpipe extraction system is the recognised control for engine running indoors.

Question 4Occupational Safety and Health in the Automotive Workshop

Which PPE is essential when using a bench grinder to sharpen a chisel?

  1. Impact-rated goggles over safety glasses Correct answer.
  2. A dust respirator and ear plugs only
  3. A full-face welding shield
  4. Anti-vibration gloves without eye protection

Explanation

Grinding throws high-speed particles that can pass around ordinary spectacles, so impact-rated goggles worn over safety glasses give the required eye protection. The grinder also produces sparks and metal dust, which the goggles shield the eyes from.

Question 5Occupational Safety and Health in the Automotive Workshop

Before starting work on a hybrid vehicle's high-voltage system, what is the correct sequence?

  1. Isolate the high-voltage battery, wait the specified time, then verify zero voltage Correct answer.
  2. Disconnect the 12 V battery and proceed without further checks
  3. Remove the service plug and immediately begin disassembly
  4. Wear rubber gloves and work on the live system with insulated tools

Explanation

High-voltage capacitors can retain a dangerous charge after isolation, so the manufacturer's specified waiting time must elapse before testing. Voltage must then be verified as zero at the test points before any work on the HV system begins.

Question 6Occupational Safety and Health in the Automotive Workshop

A trolley jack is used to lift a vehicle for a quick inspection. What must be done before any part of a person goes under the vehicle?

  1. Lower the vehicle onto rated axle stands at the specified points Correct answer.
  2. Ask a colleague to hold the jack handle steady
  3. Chock the wheels and leave the jack holding the load
  4. Place a block of wood between the jack and the sill

Explanation

A trolley jack is a lifting device, not a support device, and can lower suddenly if a seal fails. The vehicle must be transferred onto rated axle stands placed at the manufacturer's jacking points before anyone works beneath it.

Question 7Occupational Safety and Health in the Automotive Workshop

What is the primary purpose of a residual current device on a workshop socket used for portable power tools?

  1. To disconnect the supply quickly if current leaks to earth Correct answer.
  2. To limit the current drawn by the tool to its rating
  3. To convert AC supply to the voltage the tool needs
  4. To protect the tool motor from overheating under load

Explanation

An RCD monitors the difference between live and neutral current and trips when leakage to earth is detected, cutting the supply before a fatal shock occurs. It is a supplementary protection against earth faults, not an overload or voltage-control device.

Question 8Occupational Safety and Health in the Automotive Workshop

A hydraulic press is used to press a wheel bearing. Which precaution most directly reduces the risk of sudden component ejection?

  1. Wear hearing protection and stand to the side of the press
  2. Lubricate the ram with grease before every press cycle
  3. Increase pressure quickly to shorten the time under load
  4. Use a correctly sized support plate and keep the work aligned Correct answer.

Explanation

Bearings and press plates can shatter or slip out when the load is misaligned or the support is the wrong size, releasing stored energy suddenly. Correctly sized tooling and a properly aligned workpiece keep the force path contained and reduce ejection risk.

Question 9Occupational Safety and Health in the Automotive Workshop

How should used engine oil and drained coolant be handled in the workshop?

  1. Store them in labelled containers for licensed collection Correct answer.
  2. Pour them into the general waste bin once cooled
  3. Dilute them with water and discharge to the drain
  4. Mix them together to reduce the number of containers

Explanation

Used oil and coolant are hazardous wastes that must be segregated, stored in clearly labelled containers, and passed to a licensed waste contractor. Mixing streams or discharging to drains breaches environmental law and makes recycling impossible.

Question 10Occupational Safety and Health in the Automotive Workshop

A CO2 extinguisher is selected for a small fire in a petrol storage area. Why is this choice appropriate?

  1. It cools the fuel below its flash point permanently
  2. It forms a blanket that chemically reacts with petrol
  3. It is the only type that can be used outdoors
  4. It displaces oxygen and leaves no residue on the fuel Correct answer.

Explanation

CO2 smothers the fire by displacing oxygen at the surface and does not leave the conductive or contaminating residue that powder or water would. For flammable liquid fires it is suitable for small, contained incidents where the fuel surface can be covered.

Question 11Occupational Safety and Health in the Automotive Workshop

When is it acceptable to defeat an interlock guard on a tyre-changing machine?

  1. When the operator has been trained on the machine
  2. When a tyre change is urgent and the shop is busy
  3. Never; faults must be repaired before the machine is used Correct answer.
  4. When a second person watches the operation

Explanation

Interlocks exist to prevent the operator being caught in the bead-seating or clamping mechanisms, and defeating them removes that protection entirely. A defective interlock must be repaired and the machine taken out of service until it is, regardless of training or supervision.

Question 12Occupational Safety and Health in the Automotive Workshop

A technician develops dermatitis after repeated contact with solvent-based brake cleaner. Which control should be applied first under the hierarchy of controls?

  1. Post a warning sign at the cleaning bench
  2. Substitute a less hazardous aqueous cleaner where suitable Correct answer.
  3. Issue nitrile gloves to all technicians
  4. Provide barrier cream before each use

Explanation

The hierarchy of controls places elimination and substitution above PPE, because removing the hazardous agent protects everyone without relying on correct behaviour. Choosing a less hazardous cleaner where the task allows is the most effective step.

Question 13Occupational Safety and Health in the Automotive Workshop

Which condition indicates that a two-post hoist should be taken out of service immediately?

  1. The arms show light surface rust on the paint
  2. One of the arm locking pawls fails to engage Correct answer.
  3. The hoist was last inspected eight months ago
  4. The hydraulic oil level is at the minimum mark

Explanation

The arm locking pawls are the mechanical means of preventing the arms from spreading under load, so a pawl that does not engage removes a critical safety function. The hoist must be locked out and repaired before further use.

Question 14Occupational Safety and Health in the Automotive Workshop

A technician must weld a patch on a vehicle floor pan. Which combination of controls is most appropriate?

  1. Ear defenders, gloves, and a paper respirator
  2. Screens around the bay, local fume extraction, and a welding helmet with filter Correct answer.
  3. A dust mask, safety glasses, and general bay ventilation
  4. A full-face shield and opening the bay doors

Explanation

Welding produces intense UV radiation, sparks, and metal fume, so each must be controlled at source or at the person. Screening protects others from arc flash, local extraction removes fume near the arc, and a filtered helmet protects the welder's eyes and face.

Question 15Occupational Safety and Health in the Automotive Workshop

Why must a vehicle's air suspension system be depressurised according to the manufacturer's procedure before component removal?

  1. To prevent the compressor from running during the repair
  2. To reset the ride-height calibration to default
  3. To avoid stored gas or fluid releasing suddenly and causing injury Correct answer.
  4. To allow the wheel alignment to be adjusted

Explanation

Air suspension stores energy in pressurised gas or hydraulic accumulators, and releasing it uncontrolled can throw components or inject fluid. Following the specified depressurisation procedure removes that stored energy before work begins.

Question 16Occupational Safety and Health in the Automotive Workshop

What does a safety data sheet tell a mechanic that a product label alone does not?

  1. The shelf life and recommended retail packaging
  2. The retail price and supplier contact details
  3. The warranty terms for the product
  4. The first-aid measures and exposure controls for the substance Correct answer.

Explanation

The SDS provides detailed hazard, first-aid, handling, and exposure-control information required to assess risk in the workplace. A label gives only summary hazard symbols and precautions, so the SDS is needed for a full risk assessment.

Question 17Occupational Safety and Health in the Automotive Workshop

A compressed-gas cylinder is stored in the workshop. Which practice is correct?

  1. Store fuel gas and oxygen cylinders together to save space
  2. Leave regulators attached to cylinders in long-term storage
  3. Lay oxygen cylinders horizontally to save space
  4. Secure upright cylinders with a chain or strap and keep caps fitted Correct answer.

Explanation

Upright, secured cylinders cannot topple and shear the valve, and valve protection caps prevent impact damage during storage. Fuel gas and oxygen must also be segregated to prevent a fire escalating between them.

Question 18Occupational Safety and Health in the Automotive Workshop

A mechanic notices that a portable angle grinder's cable has a cut through the outer sheath exposing inner conductors. What is the correct action?

  1. Wrap the cut with insulating tape and continue using the tool
  2. Use the tool only for light jobs until the end of the shift
  3. Continue using it only on a socket protected by an RCD
  4. Withdraw the tool from use, tag it, and report the defect Correct answer.

Explanation

Damaged insulation on a portable tool is a serious electric-shock hazard and cannot be repaired with tape as a permanent fix. The tool must be withdrawn from service, tagged as defective, and repaired or replaced before use.

Question 19Occupational Safety and Health in the Automotive Workshop

A workshop's risk assessment for brake servicing identifies inhalation of brake dust as a hazard. Which control most effectively protects the technician at the point of exposure?

  1. A general exhaust fan running in the bay
  2. Wet methods or a dust-extraction brake vacuum, plus suitable respiratory protection Correct answer.
  3. A warning sign on the brake bench
  4. Rotating staff so no one services brakes every day

Explanation

Brake dust containing asbestos or other fibres becomes airborne when disturbed, so wetting components or using a dedicated brake vacuum captures it at source. Suitable respiratory protection then covers any residual exposure during the task.

Question 20Occupational Safety and Health in the Automotive Workshop

Which behaviour best demonstrates correct manual handling when lifting a heavy gearbox from a bench?

  1. Hold the load at arm's length to keep it clear of the body
  2. Lift with a jerking motion to overcome the initial weight
  3. Bend at the waist, twist, and lift quickly to clear the bench
  4. Keep the load close, bend the knees, and lift with a straight back Correct answer.

Explanation

Keeping the load close reduces the moment on the lower back, and bending the knees lets the leg muscles do the lifting with the spine kept neutral. Twisting or jerking under load sharply raises the risk of back injury.

Question 21Workshop Tools, Equipment and Measuring Instruments

Which measuring instrument is designed specifically to measure the internal diameter of a cylinder bore?

  1. Feeler gauge
  2. Inside micrometer Correct answer.
  3. Vernier caliper depth rod
  4. Outside micrometer

Explanation

An inside micrometer has measuring faces arranged to contact the internal walls of a bore, so it reads internal diameter directly. An outside micrometer measures external dimensions only. A depth rod measures depth, and a feeler gauge measures gap clearance.

Question 22Workshop Tools, Equipment and Measuring Instruments

A torque wrench is being stored after use. Which practice keeps its calibration accurate?

  1. Store it with the handle immersed in oil
  2. Store it locked at the last torque value used
  3. Store it hanging by the drive square
  4. Store it with the setting wound down to its lowest scale value Correct answer.

Explanation

Spring-type torque wrenches hold calibration best when the spring is unloaded, so the scale is wound back to its lowest setting before storage. Leaving it loaded fatigues the spring and drifts the setting. Hanging by the drive square or soaking the handle can also damage the tool.

Question 23Workshop Tools, Equipment and Measuring Instruments

What is the reading of a metric outside micrometer whose barrel shows 12 mm, with the thimble line aligned to the 35th division?

  1. 12.50 mm
  2. 15.50 mm
  3. 12.035 mm
  4. 12.35 mm Correct answer.

Explanation

On a metric micrometer with 0.01 mm thimble graduations, the barrel gives whole and half millimetres and the thimble gives hundredths. Adding 12 mm to 35 divisions times 0.01 mm gives 12.35 mm. The thimble value is added, not appended as thousandths.

Question 24Workshop Tools, Equipment and Measuring Instruments

A technician needs to check the runout of a brake disc while it is mounted on the vehicle. Which tool is most appropriate?

  1. A steel rule
  2. A magnetic-base dial test indicator Correct answer.
  3. A vernier caliper
  4. A telescopic gauge

Explanation

A dial test indicator mounted on a magnetic base can be set against the disc face and shows small variations as the disc rotates, which is exactly what runout measurement requires. A steel rule and caliper lack the resolution and cannot follow rotation. A telescopic gauge transfers a bore size for later measurement.

Question 25Workshop Tools, Equipment and Measuring Instruments

Which instrument would be selected to measure the clearance between a valve stem and its guide?

  1. Torque angle gauge
  2. Small-hole bore gauge and outside micrometer Correct answer.
  3. Feeler gauge
  4. Plastigauge

Explanation

Valve stem-to-guide clearance is found by measuring the guide bore with a small-hole bore gauge and the stem with an outside micrometer, then subtracting. A feeler gauge cannot enter that annular gap reliably. Plastigauge is used for bearing oil clearance, and a torque angle gauge measures rotation.

Question 26Workshop Tools, Equipment and Measuring Instruments

A dial test indicator reads 0.04 mm on one side of a shaft and 0.10 mm on the opposite side after rotation. What is the total indicated runout?

  1. 0.10 mm
  2. 0.14 mm
  3. 0.06 mm Correct answer.
  4. 0.04 mm

Explanation

Total indicated runout is the difference between the maximum and minimum readings as the part rotates, so 0.10 mm minus 0.04 mm equals 0.06 mm. Summing the readings would describe the full sweep of the needle, not runout. The individual readings alone do not give runout.

Question 27Workshop Tools, Equipment and Measuring Instruments

Which tool is used to measure the outside diameter of a piston skirt to check for wear?

  1. Dial bore gauge
  2. Telescopic gauge
  3. Feeler gauge
  4. Outside micrometer Correct answer.

Explanation

An outside micrometer is the standard tool for measuring external diameters such as a piston skirt at a specified height. A telescopic gauge and dial bore gauge measure internal bores. A feeler gauge measures gaps.

Question 28Workshop Tools, Equipment and Measuring Instruments

What is the main purpose of a torque angle gauge when tightening a cylinder head bolt?

  1. To measure the final torque value reached
  2. To verify the bolt thread pitch
  3. To apply a specified further rotation after the bolt reaches its initial torque Correct answer.
  4. To check the flatness of the head surface

Explanation

Many modern head bolts are tightened to a low initial torque and then rotated through a specified angle, which stretches the bolt into its elastic range for a consistent clamp load. A torque angle gauge measures that rotation, not torque. Thread pitch and surface flatness are checked with other tools.

Question 29Workshop Tools, Equipment and Measuring Instruments

A vernier caliper main scale reads 24 mm and the vernier scale line that coincides is the 6th division, with each vernier division equal to 0.02 mm. What is the measurement?

  1. 24.06 mm
  2. 24.24 mm
  3. 24.60 mm
  4. 24.12 mm Correct answer.

Explanation

The vernier reading is the coinciding division multiplied by the least count, so 6 times 0.02 mm equals 0.12 mm. Adding this to the 24 mm main scale reading gives 24.12 mm. The main scale value must be added to, not combined with, the vernier fraction.

Question 30Workshop Tools, Equipment and Measuring Instruments

Which instrument is used to check the flatness of a cylinder head surface?

  1. A dial bore gauge
  2. A telescopic gauge
  3. A straightedge used with a feeler gauge Correct answer.
  4. A torque wrench

Explanation

Head flatness is checked by laying a precision straightedge across the surface in several directions and probing any gap with a feeler gauge. A dial bore gauge and telescopic gauge measure bores, and a torque wrench tightens fasteners.

Question 31Workshop Tools, Equipment and Measuring Instruments

A compression tester shows a much lower reading on one cylinder than on the others. Which follow-up step best confirms whether the loss is past the piston rings or the valves?

  1. Retest the engine when cold only
  2. Add a small amount of oil to the cylinder and repeat the test Correct answer.
  3. Repeat the test with a different gauge brand
  4. Increase the engine idle speed and retest

Explanation

Adding a few millilitres of oil temporarily seals worn rings, so if compression rises the rings are the likely cause. If the reading stays low, the leak is more likely past valves or the head gasket. Changing gauge brand or idle speed does not isolate the source.

Question 32Workshop Tools, Equipment and Measuring Instruments

Which item of workshop equipment is used to lift an engine safely out of a vehicle bay?

  1. A transmission jack
  2. A trolley jack alone
  3. A pair of axle stands
  4. An engine crane rated above the engine weight Correct answer.

Explanation

An engine crane is designed to lift and suspend a load vertically, and it must be rated above the engine weight with a margin. A trolley jack lifts at a low point and is unstable for suspended loads. Axle stands support a raised vehicle, and a transmission jack is for gearboxes.

Question 33Workshop Tools, Equipment and Measuring Instruments

A hydraulic workshop press is being used to press a bearing from a shaft. Which practice protects both the operator and the components?

  1. Stand directly in line with the ram to watch the work
  2. Hold the workpiece steady by hand during pressing
  3. Press against the outer race only when removing an inner race
  4. Use a correctly sized support and keep hands clear of the press line Correct answer.

Explanation

A press concentrates large force, so the workpiece must be supported squarely with correct adapters and hands kept away from the crush line. Holding the work by hand or standing in line with the ram exposes the operator to sudden release. Pressing the wrong race can damage the bearing.

Question 34Workshop Tools, Equipment and Measuring Instruments

Which instrument is used to measure the thickness of a brake pad friction material?

  1. Torque angle gauge
  2. Telescopic gauge
  3. Vernier caliper Correct answer.
  4. Dial bore gauge

Explanation

A vernier caliper or a dedicated pad thickness gauge measures the friction material thickness directly. A dial bore gauge and telescopic gauge are for internal bores, and a torque angle gauge measures fastener rotation.

Question 35Workshop Tools, Equipment and Measuring Instruments

A micrometer reads 0.00 mm when its anvils are closed, but reads 0.03 mm when checked against a 25 mm standard. What does this indicate?

  1. A zero error that must be corrected or compensated for Correct answer.
  2. That the ratchet stop is faulty
  3. That the standard is worn
  4. That the thimble is loose on its spindle

Explanation

When the anvils close at zero but a known standard reads 0.03 mm high, the instrument has a zero error that must be adjusted or subtracted from readings. A worn standard would not explain the closed-anvil zero. Loose thimbles and faulty ratchets produce inconsistent readings, not a steady offset.

Question 36Workshop Tools, Equipment and Measuring Instruments

What is the function of the ratchet stop on a micrometer?

  1. To zero the instrument
  2. To apply a consistent measuring force Correct answer.
  3. To lock the spindle after measurement
  4. To convert metric readings to imperial

Explanation

The ratchet stop slips at a set force so each measurement is taken with the same pressure, improving repeatability. The spindle lock holds a reading, but that is a separate feature. It does not convert units or zero the instrument.

Question 37Workshop Tools, Equipment and Measuring Instruments

A technician must check the end float of a crankshaft. Which method gives a direct reading?

  1. A feeler gauge between the pulley and the block
  2. A compression tester
  3. A dial test indicator with its plunger against the crank end Correct answer.
  4. A torque wrench on the crank bolt

Explanation

End float is axial movement, so a dial test indicator placed against the crank end and zeroed, then the crank levered back and forth, gives the total movement directly. A feeler gauge at the pulley cannot access the true thrust faces. A torque wrench and compression tester measure unrelated quantities.

Question 38Workshop Tools, Equipment and Measuring Instruments

Which tool is used to measure the diameter of a cylinder bore accurately after honing?

  1. Feeler gauge
  2. Dial bore gauge set to the bore size with a micrometer Correct answer.
  3. Steel rule
  4. Outside micrometer alone

Explanation

A dial bore gauge is zeroed against a micrometer set to the nominal bore size, then inserted into the bore to show deviation and taper. An outside micrometer cannot reach inside the bore. A feeler gauge and steel rule lack the required resolution.

Question 39Workshop Tools, Equipment and Measuring Instruments

A workshop is selecting a torque wrench for a fastener specified at 40 N·m. Which choice is most appropriate?

  1. A wrench whose minimum is 40 N·m
  2. A wrench whose mid-range covers 40 N·m Correct answer.
  3. A wrench rated far above the required value
  4. A wrench whose maximum is 40 N·m

Explanation

Torque wrenches are most accurate in the middle of their range, so a wrench whose mid-range covers the specified value gives the best accuracy. Using a wrench at its maximum or minimum pushes it toward the less accurate ends of its scale. A wrench rated far above the value operates at the bottom of its range.

Question 40Workshop Tools, Equipment and Measuring Instruments

Which instrument is used to measure the gap between a spark plug electrode and its ground strap?

  1. Feeler gauge or wire gauge Correct answer.
  2. Torque angle gauge
  3. Dial bore gauge
  4. Vernier caliper

Explanation

A feeler gauge or dedicated wire-type spark plug gauge is thin enough to be inserted into the electrode gap and gives a direct clearance reading. A vernier caliper is too bulky for that gap, and the other tools measure bores or rotation.

Question 41Engine Systems: Construction, Operation and Maintenance

On a four-stroke engine, which valve is open during the stroke that draws the air-fuel mixture into the cylinder?

  1. Exhaust valve
  2. Both valves equally
  3. Neither valve
  4. Intake valve Correct answer.

Explanation

The intake stroke is the downward piston movement during which the intake valve is held open so the fresh charge can be drawn into the cylinder. The exhaust valve stays closed throughout this stroke and only opens near the end of the power stroke.

Question 42Engine Systems: Construction, Operation and Maintenance

What is the primary function of the piston rings fitted to a piston?

  1. Drive the oil pump
  2. Balance the crankshaft
  3. Seal combustion gases and control oil on the bore Correct answer.
  4. Absorb torsional vibration

Explanation

Compression rings seal combustion pressure against the cylinder wall, while the oil control ring scrapes excess oil back down the bore. Together they keep gas tightness and oil consumption within design limits.

Question 43Engine Systems: Construction, Operation and Maintenance

In a liquid-cooled engine, what is the main job of the thermostat?

  1. Drive the water pump impeller
  2. Regulate coolant flow to keep the engine at operating temperature Correct answer.
  3. Pressurise the cooling system
  4. Filter debris from the coolant

Explanation

The thermostat is a temperature-sensitive valve that stays closed while the engine is cold and opens as coolant reaches its rated temperature. This shortens warm-up and holds the engine near its designed operating range.

Question 44Engine Systems: Construction, Operation and Maintenance

What does the camshaft of a four-stroke engine control?

  1. The fuel pressure at the injectors
  2. The torque delivered to the gearbox
  3. The timing and lift of the valves Correct answer.
  4. The ignition timing at the spark plug

Explanation

The camshaft lobes push the valves open at the correct point in the cycle and determine how far they open. Its rotational speed is half of the crankshaft speed on a four-stroke engine.

Question 45Engine Systems: Construction, Operation and Maintenance

Which component converts the reciprocating motion of the piston into rotary motion?

  1. Connecting rod and crankshaft Correct answer.
  2. Camshaft and pushrod
  3. Flywheel and clutch
  4. Timing belt and tensioner

Explanation

The connecting rod links the piston to the crankshaft journal, and the crankshaft converts the straight-line thrust into rotation. This is the core mechanism of the reciprocating engine.

Question 46Engine Systems: Construction, Operation and Maintenance

What is the purpose of the valve clearance specified in a mechanical valvetrain?

  1. Allow for thermal expansion so the valve seats fully when hot Correct answer.
  2. Keep the valve spring compressed at rest
  3. Reduce oil pressure at the camshaft
  4. Increase valve lift at high speed

Explanation

A cold clearance is set so that when the engine reaches operating temperature and the metal expands, the valve still closes fully on its seat. Too little clearance can hold a valve open and cause compression loss or burning.

Question 47Engine Systems: Construction, Operation and Maintenance

Which of these is a routine maintenance item that protects the engine by removing particles from the intake air?

  1. Oil dipstick
  2. Crankcase breather filter only
  3. Air filter element Correct answer.
  4. Radiator cap

Explanation

The air filter element traps dust and grit before it reaches the intake and cylinders, reducing bore and valve wear. It is inspected and replaced on a mileage or condition basis.

Question 48Engine Systems: Construction, Operation and Maintenance

What does engine 'valve overlap' refer to?

  1. The distance the valve travels below the seat
  2. The clearance between valve stem and guide
  3. A period when intake and exhaust valves are both open near top dead centre Correct answer.
  4. The gap between tappet and cam base circle

Explanation

Overlap occurs around top dead centre when the exhaust valve has not yet closed and the intake valve has already begun to open. It helps scavenge exhaust gas and improve cylinder filling at speed.

Question 49Engine Systems: Construction, Operation and Maintenance

During a compression test on a warm petrol engine, one cylinder reads about 30% lower than the others and does not improve when a little oil is added. What does this most likely indicate?

  1. A faulty spark plug
  2. An over-rich mixture
  3. Worn piston rings
  4. Leaking valves or head gasket Correct answer.

Explanation

If adding oil temporarily seals the rings, low compression that persists points to leakage past valves or the head gasket. A wet test that does not raise the reading rules out ring sealing as the main cause.

Question 50Engine Systems: Construction, Operation and Maintenance

An engine overheats only when the vehicle is stationary in traffic but cools once moving. Which fault best fits this symptom?

  1. Low coolant concentration of antifreeze
  2. Thermostat stuck open
  3. Cooling fan not operating Correct answer.
  4. Radiator cap releasing too early

Explanation

When airflow from vehicle motion is lost, the electric or viscous fan must pull air through the radiator. If it fails, temperature climbs at idle and falls again once ram air returns.