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SOLAS Heavy Vehicle Mechanic study materials
SOLAS Heavy Vehicle Mechanic study resources

SOLAS Heavy Vehicle Mechanic practice questions

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Question 1Heavy Vehicle Mechanic (craft apprenticeship curriculum)

A heavy vehicle mechanic is checking a truck tyre and finds the tread depth at the deepest groove is 1.0 mm. What is the correct action under Australian heavy vehicle tyre requirements?

  1. The tyre may remain in service until the next scheduled service interval
  2. The tyre is acceptable because the minimum legal tread depth is 1.0 mm
  3. The tyre must be removed from service because the minimum legal tread depth is 1.5 mm Correct answer.
  4. The tyre may remain in service if it is fitted to a non-steering axle

Explanation

For heavy vehicles in Australia the minimum legal tread depth is 1.5 mm across the tread pattern in the major grooves. A tyre worn to 1.0 mm is below that limit and is unroadworthy, so it must be replaced regardless of axle position.

Question 2Heavy Vehicle Mechanic (craft apprenticeship curriculum)

When tensioning a wheel nut on a heavy vehicle fitted with a two-piece flange nut and stud, which statement describes correct practice?

  1. Overtighten deliberately so the nut does not loosen between services
  2. Apply the specified torque with a calibrated torque wrench, following the manufacturer's sequence Correct answer.
  3. Tighten with a rattle gun until the nut stops turning, then check by hand
  4. Torque the nuts while the wheel is jacked clear of the ground

Explanation

Wheel nuts must be tensioned to the manufacturer's specified torque using a calibrated torque wrench in the prescribed sequence. Impact tools cannot reliably achieve or confirm the correct clamp load and can over-stretch studs.

Question 3Heavy Vehicle Mechanic (craft apprenticeship curriculum)

What is the primary function of the air dryer in a heavy vehicle air brake system?

  1. To remove moisture and oil contamination from compressed air before it reaches the reservoirs Correct answer.
  2. To lubricate the brake valves with atomised oil
  3. To cool the compressor discharge to ambient temperature
  4. To increase reservoir pressure above governor cut-out

Explanation

The air dryer uses a desiccant cartridge to remove water vapour and carry-over oil from the compressed air. Dry air prevents internal corrosion and ice formation in valves and lines.

Question 4Heavy Vehicle Mechanic (craft apprenticeship curriculum)

A mechanic is preparing to work under a raised tipper body supported only by the hydraulic hoist. What is the correct safety practice?

  1. Place a wheel chock under one rear tyre and proceed
  2. Lower the body until it just rests on the hoist ram
  3. Ask a second person to hold the control lever in the raised position
  4. Fit the manufacturer's body props or safety struts before entering the area beneath the body Correct answer.

Explanation

Hydraulic systems can lose pressure through seal failure or hose burst, so the raised body must be mechanically secured with the manufacturer's props. Never rely on hydraulic pressure alone to protect a person under a suspended load.

Question 5Heavy Vehicle Mechanic (craft apprenticeship curriculum)

Which component converts the rotary motion of the steering wheel into linear movement of the steering linkage in a heavy vehicle with a recirculating ball steering gear?

  1. The kingpin
  2. The steering damper
  3. The drag link ball joint
  4. The sector shaft and pitman arm Correct answer.

Explanation

In a recirculating ball gearbox the ball nut moves along the worm shaft and rotates the sector shaft, which turns the pitman arm. The pitman arm then transfers that rotary output into linear movement of the drag link and steering linkage.

Question 6Heavy Vehicle Mechanic (craft apprenticeship curriculum)

A diesel engine has excessive blue-white smoke at idle that clears as the engine warms. Which cause is most consistent with this symptom?

  1. A restricted air filter element
  2. Low coolant concentration in the radiator
  3. Worn valve stem seals allowing oil to enter the cylinders Correct answer.
  4. A faulty exhaust gas recirculation valve stuck open

Explanation

Oil seeping past worn valve stem seals pools in the cylinders while the engine is stopped and burns off as blue-white smoke on start-up. Once the seals warm and expand, the smoke reduces, which matches the described symptom.

Question 7Heavy Vehicle Mechanic (craft apprenticeship curriculum)

Which document should a mechanic consult to find the correct tightening torque for a specific fastener on a heavy vehicle?

  1. The vehicle registration certificate
  2. The workshop's general tool inventory
  3. The driver's pre-start checklist
  4. The manufacturer's workshop or service manual for that vehicle model Correct answer.

Explanation

Torque specifications are model and fastener specific and are published in the manufacturer's service information. Generic or guessed values risk fastener failure or component damage.

Question 8Heavy Vehicle Mechanic (craft apprenticeship curriculum)

What is the purpose of a differential lock in a heavy vehicle drive axle?

  1. To reduce wheel bearing preload at high speed
  2. To increase the final drive ratio for higher top speed
  3. To disconnect the tailshaft during towing
  4. To lock the differential gears so both wheels on the axle turn together for improved traction Correct answer.

Explanation

A differential lock mechanically couples the side gears so both wheels rotate at the same speed, preventing one wheel from spinning when traction is lost. It should only be engaged when the surface allows some wheel slip.

Question 9Heavy Vehicle Mechanic (craft apprenticeship curriculum)

A mechanic is diagnosing a heavy vehicle that pulls to the left under braking. Which inspection is the most logical first step?

  1. Adjust the rear brake slack adjusters only
  2. Increase tyre pressure on the left front tyre
  3. Replace both front brake drums as a matched pair
  4. Compare brake chamber stroke and lining condition on both sides of the front axle Correct answer.

Explanation

Uneven braking force causes a pull, so the first step is to compare brake chamber pushrod stroke, lining wear and contamination on both sides. This identifies whether one side is over- or under-braking before any parts are replaced.

Question 10Heavy Vehicle Mechanic (craft apprenticeship curriculum)

During a cooling system pressure test, the gauge holds pressure but the coolant level in the radiator drops slowly over 20 minutes with no external leak visible. Which cause should be investigated?

  1. A faulty radiator cap that releases pressure too early
  2. A slipping water pump drive belt
  3. An internal leak such as a failed head gasket or cracked cylinder head Correct answer.
  4. A thermostat stuck in the open position

Explanation

A system that holds pressure but loses coolant without an external leak is likely losing it internally, for example through a head gasket or cracked casting into a cylinder or oil gallery. Combustion gas testing and oil inspection help confirm this.

Question 11Heavy Vehicle Mechanic (craft apprenticeship curriculum)

What is the effect of excessive valve lash on a diesel engine?

  1. Increased valve lift and longer duration, causing valve-to-piston contact
  2. Advanced injection timing and higher cylinder pressure
  3. No effect on engine performance but reduced oil pressure
  4. Reduced valve lift and duration, causing poor breathing and increased noise Correct answer.

Explanation

Excessive lash delays valve opening and reduces effective lift, so the engine breathes poorly and the valve train becomes noisy. The clearance must be reset to the manufacturer's specification with the engine at the stated temperature.

Question 12Heavy Vehicle Mechanic (craft apprenticeship curriculum)

A heavy vehicle has a persistent fault code for low turbocharger boost. A smoke test shows no leaks in the charge air piping. Which component should be checked next?

  1. The wastegate actuator and boost control circuit Correct answer.
  2. The engine coolant thermostat
  3. The fuel tank vent valve
  4. The rear axle breather

Explanation

Once charge air leaks are ruled out, the next suspect is the boost control system, including the wastegate actuator, solenoid and associated hoses. A wastegate stuck open will bleed exhaust gas around the turbine and limit boost.

Question 13Heavy Vehicle Mechanic (craft apprenticeship curriculum)

Which inspection item is most important when assessing a heavy vehicle's spring brake (park brake) chambers?

  1. Checking the length of the air supply hose only
  2. Checking that the chamber is painted with the vehicle's livery
  3. Checking the colour of the chamber housing
  4. Checking that the spring brake is caged or released safely before dismantling Correct answer.

Explanation

Spring brake chambers store large spring energy and can release violently if dismantled without caging or disarming the spring. The correct procedure is to compress and cage the spring or replace the complete chamber per manufacturer instructions.

Question 14Heavy Vehicle Mechanic (craft apprenticeship curriculum)

A truck's automatic transmission is slipping under load. Which diagnostic step best separates a hydraulic control fault from a mechanical wear fault?

  1. Check the tyre pressures on the drive axle
  2. Adjust the throttle position sensor linkage
  3. Replace the transmission fluid and road test
  4. Measure line pressure and compare with specification under load Correct answer.

Explanation

Line pressure testing shows whether the hydraulic system can apply clutches with sufficient force. If pressure is within specification but the transmission still slips, mechanical wear in the clutch packs is indicated.

Question 15Heavy Vehicle Mechanic (craft apprenticeship curriculum)

What is the correct procedure for checking the oil level in a heavy vehicle differential?

  1. Remove the filler plug with the vehicle level and check that oil is at or just below the filler hole Correct answer.
  2. Drain the oil and measure the volume against the specification
  3. Check the oil level only after the differential has reached operating temperature
  4. Check the oil level while the vehicle is on a steep incline

Explanation

The filler plug on most differentials acts as the level indicator. With the vehicle level, oil should be at or just below the bottom of the filler hole. Checking on an incline gives a false reading.

Question 16Heavy Vehicle Mechanic (craft apprenticeship curriculum)

A heavy vehicle's battery is flat after standing overnight. A parasitic drain test shows 0.8 A with all accessories off. Which is the most appropriate next step?

  1. Fit a higher-capacity battery
  2. Isolate circuits one at a time using a clamp meter or by removing fuses to locate the drain Correct answer.
  3. Replace the battery immediately
  4. Increase the alternator belt tension

Explanation

A normal parasitic drain is typically well under 0.1 A, so 0.8 A indicates a fault. Isolating circuits with a clamp meter or by pulling fuses identifies which circuit is drawing current before any parts are replaced.

Question 17Heavy Vehicle Mechanic (craft apprenticeship curriculum)

Which statement correctly describes the function of a slack adjuster in an air brake system?

  1. It stores compressed air for emergency braking
  2. It converts the linear pushrod stroke of the brake chamber into rotary motion to apply the brake shoe Correct answer.
  3. It regulates the pressure delivered to the brake chambers
  4. It releases the spring brake when air pressure is applied

Explanation

The slack adjuster is a lever arm on the camshaft that converts the brake chamber pushrod's linear stroke into rotation of the S-cam or wedge. It also provides the adjustment that compensates for lining wear.

Question 18Heavy Vehicle Mechanic (craft apprenticeship curriculum)

A mechanic is replacing a front wheel bearing on a heavy vehicle steer axle. Which practice is essential to prevent premature failure?

  1. Reuse the old seal if it looks undamaged
  2. Pack the bearing with as much grease as the hub will hold
  3. Tighten the adjusting nut fully to remove all clearance
  4. Set the bearing end float or preload to the manufacturer's specification and use the correct seal Correct answer.

Explanation

Correct bearing end float or preload is specified by the manufacturer and must be measured, often with a dial indicator. The correct seal prevents lubricant loss and contaminant entry, both of which cause early failure.

Question 19Heavy Vehicle Mechanic (craft apprenticeship curriculum)

Which of the following best describes the purpose of a pre-start inspection on a heavy vehicle?

  1. To identify defects that could affect safe operation before the vehicle is used on the road Correct answer.
  2. To complete scheduled servicing tasks
  3. To verify the driver's licence category
  4. To record the vehicle's fuel consumption for the day

Explanation

A pre-start inspection is a daily check of tyres, brakes, lights, fluids and couplings to detect defects before the vehicle is driven. It is a safety control, not a substitute for scheduled maintenance.

Question 20Heavy Vehicle Mechanic (craft apprenticeship curriculum)

A heavy vehicle's engine overheats only when climbing long grades with a loaded trailer. Which cause is most likely?

  1. A partially blocked radiator core or faulty fan drive reducing heat rejection under high load Correct answer.
  2. A thermostat stuck open
  3. Low tyre pressure on the trailer
  4. A faulty radiator cap rated above specification

Explanation

Overheating confined to high-load conditions points to inadequate heat rejection, such as a restricted radiator core or a viscous fan drive that is not engaging. Both reduce the system's ability to shed heat when demand is highest.

Question 21Heavy Vehicle Mechanic (craft apprenticeship curriculum)

During a brake performance test, a heavy vehicle's air pressure builds slowly from 0 to governor cut-out. Which component is the most likely cause?

  1. A misadjusted slack adjuster
  2. A leaking spring brake chamber
  3. A worn or leaking compressor discharge valve or restricted discharge line Correct answer.
  4. A faulty low-pressure warning switch

Explanation

Slow pressure build-up indicates the compressor is not delivering air efficiently, commonly due to worn valves, leaking discharge lines or a restricted dryer. Brake chamber or warning switch faults would not slow the build rate.

Question 22Heavy Vehicle Mechanic (craft apprenticeship curriculum)

A mechanic observes that a heavy vehicle's rear axle has a whine that is loudest on overrun (deceleration) and changes pitch with road speed but not engine speed. Which component is the most likely source?

  1. The differential crown wheel and pinion mesh Correct answer.
  2. The engine turbocharger
  3. The power steering pump
  4. The gearbox input shaft bearing

Explanation

A noise that varies with road speed and is loudest on overrun points to the final drive, where the crown wheel and pinion load reverses. Turbocharger and gearbox input noises track engine speed, and the steering pump noise tracks steering input.

Question 23Heavy Vehicle Mechanic (craft apprenticeship curriculum)

A heavy vehicle equipped with electronically controlled air suspension sits low on one side after being parked overnight. Which diagnostic approach is most appropriate?

  1. Disconnect the height control valve and drive the vehicle
  2. Check for air leaks at the affected bellows, height control valve and fittings, and inspect the height sensor linkage Correct answer.
  3. Increase the ride height setting in the ECM
  4. Replace both air springs on the affected axle without testing

Explanation

A single corner dropping overnight indicates an air leak or a faulty height control valve or sensor linkage on that side. Leak testing and linkage inspection identify the fault before parts are replaced.

Question 24Heavy Vehicle Mechanic (craft apprenticeship curriculum)

Which statement about the use of a calibrated torque wrench is correct?

  1. It remains accurate indefinitely as long as it is not dropped
  2. It should be stored at its lowest setting and checked for calibration at defined intervals Correct answer.
  3. It should be stored at its highest setting to keep the spring exercised
  4. It can be used as a breaker bar without affecting accuracy

Explanation

Storing a torque wrench at its lowest setting prevents the internal spring from taking a permanent set, and periodic calibration checks confirm it still meets specification. Using it as a breaker bar or relying on it indefinitely risks inaccurate torque.

Question 25Heavy Vehicle Mechanic (craft apprenticeship curriculum)

A heavy vehicle has a fault where the engine derates and logs a high exhaust gas temperature code under load. Which factor is most likely to cause excessive exhaust gas temperature?

  1. An over-cooled intake charge
  2. Over-fuelling or retarded injection timing causing late combustion Correct answer.
  3. A worn clutch release bearing
  4. A blocked fuel return line to the tank

Explanation

Excess fuel or late combustion releases heat into the exhaust rather than converting it to work, raising exhaust gas temperature. The ECM derates the engine to protect the turbocharger and exhaust valves.

Question 26Heavy Vehicle Mechanic (craft apprenticeship curriculum)

A heavy vehicle mechanic is about to lift a loaded prime mover with a two-post hoist. Which check must be completed before the vehicle is raised?

  1. Confirm the hoist's rated capacity exceeds the vehicle's gross weight and that the lifting points are correctly positioned Correct answer.
  2. Remove the wheel chocks so the vehicle can settle on the hoist arms
  3. Ask the driver to remain in the cab to operate the brakes during lifting
  4. Raise the vehicle quickly to maximum height to save time

Explanation

A hoist must only be used within its rated capacity, and the vehicle's centre of gravity and manufacturer lifting points must align with the hoist arms to prevent tipping. Chocks and cab occupants are removed or controlled per workshop procedure before lifting.

Question 27Heavy Vehicle Mechanic (craft apprenticeship curriculum)

When jacking a heavy vehicle axle to change a wheel, where should the jack be placed?

  1. Under the sump to spread the load
  2. Under the body panel nearest the wheel being changed
  3. Under the axle beam or manufacturer's designated jacking point, on firm level ground with the wheels chocked Correct answer.
  4. Under the fuel tank for a wide stable base

Explanation

Jacks must bear on structural points designed for the load, such as the axle beam, with the vehicle on level firm ground and the remaining wheels chocked. Fuel tanks, sumps and body panels are not load-bearing and can be crushed or punctured.

Question 28Heavy Vehicle Mechanic (craft apprenticeship curriculum)

What is the primary function of a heavy vehicle's air dryer in the compressed air brake system?

  1. To remove moisture and oil contamination from the compressed air before it reaches the reservoirs Correct answer.
  2. To increase the compressor's delivery pressure
  3. To regulate the engine's idle speed
  4. To cool the brake chambers during heavy braking

Explanation

The air dryer contains a desiccant that absorbs water vapour and filters oil carry-over from the compressor, protecting valves and reservoirs from corrosion and ice. It does not generate pressure or control engine speed.

Question 29Heavy Vehicle Mechanic (craft apprenticeship curriculum)

Which component converts the rotational force of the steering wheel into linear movement that steers the road wheels on a heavy truck?

  1. The wheel bearing
  2. The steering gearbox and drag link assembly Correct answer.
  3. The stabiliser bar
  4. The kingpin

Explanation

The steering gearbox multiplies driver effort and converts rotary input into linear motion, transmitted through the drag link and tie rod to the steering arms. The kingpin is the pivot on the axle and does not transmit steering input.

Question 30Heavy Vehicle Mechanic (craft apprenticeship curriculum)

What does the term 'gross vehicle mass' (GVM) mean for a heavy vehicle?

  1. The maximum permissible mass of the vehicle including its load, as specified by the manufacturer Correct answer.
  2. The mass measured at the steer axle only
  3. The mass of the payload only
  4. The mass of the vehicle when empty with a full tank of fuel

Explanation

GVM is the maximum design mass of the vehicle plus its load, set by the manufacturer and used for compliance and load planning. Tare mass is the empty vehicle mass, and axle mass limits are separate figures.

Question 31Heavy Vehicle Mechanic (craft apprenticeship curriculum)

Which type of oil is typically specified for a heavy vehicle's manual transmission to handle high torque and gear contact pressures?

  1. A gear oil of the grade and specification listed by the transmission manufacturer Correct answer.
  2. Automatic transmission fluid in all cases
  3. An engine oil of the lowest available viscosity
  4. Hydraulic jack oil

Explanation

Manual transmissions require a lubricant meeting the manufacturer's specification, usually a gear oil with extreme-pressure additives for high contact loads. Engine oil, ATF or hydraulic oil may lack the correct additive package and viscosity.

Question 32Heavy Vehicle Mechanic (craft apprenticeship curriculum)

A heavy vehicle mechanic is measuring brake drum diameter during a brake overhaul. Which measurement indicates the drum must be replaced?

  1. The drum has a small amount of surface rust from standing
  2. The drum has a light surface glaze that can be deglazed
  3. The drum is within the manufacturer's maximum rebore diameter and shows no cracks
  4. The drum exceeds the manufacturer's maximum allowable diameter or shows heat cracks Correct answer.

Explanation

Brake drums have a manufacturer maximum diameter beyond which the friction surface is too thin to dissipate heat safely, and cracks are a rejection criterion. Light glaze or surface rust can usually be remedied without replacement.

Question 33Heavy Vehicle Mechanic (craft apprenticeship curriculum)

What is the purpose of a wheel alignment check on a heavy vehicle steer axle?

  1. To adjust the engine's road speed governor
  2. To ensure the wheels point in the correct direction relative to each other and the chassis, minimising tyre scrub and steering pull Correct answer.
  3. To balance the brake chambers
  4. To set tyre inflation pressures

Explanation

Wheel alignment sets toe, camber, caster and thrust angle so the tyres roll without excessive scrub and the vehicle tracks straight. It does not set tyre pressures, engine speed or brake components.

Question 34Heavy Vehicle Mechanic (craft apprenticeship curriculum)

A heavy vehicle's engine oil pressure warning light illuminates at idle when hot but extinguishes as engine speed rises. Which explanation is most consistent with this behaviour?

  1. The alternator belt is slipping
  2. Oil pressure is lower at idle when the oil is hot and thin, which can indicate worn bearings or a weak oil pump Correct answer.
  3. The engine coolant is overfull
  4. The oil pressure sender is disconnected

Explanation

Hot oil has lower viscosity, so idle oil pressure drops; if it falls below the warning threshold only when hot, worn bearing clearances or a tired pump are likely. The condition improving with rpm supports a pressure-versus-speed relationship rather than an electrical fault.

Question 35Heavy Vehicle Mechanic (craft apprenticeship curriculum)

A mechanic is setting up a dial indicator to measure brake drum runout. Which practice ensures an accurate reading?

  1. Measure only at the drum's outer edge
  2. Measure with the drum removed from the hub
  3. Mount the indicator on the drum itself so it moves with the drum
  4. Mount the indicator rigidly to a fixed point on the axle and zero the plunger on the friction surface Correct answer.

Explanation

Runout is measured relative to a fixed reference, so the indicator base must be rigidly mounted to the axle or hub and its plunger placed on the friction surface. Mounting on the drum makes the indicator move with the measured part, cancelling the reading.

Question 36Heavy Vehicle Mechanic (craft apprenticeship curriculum)

During a road test, a heavy vehicle's engine surges and loses power momentarily when the accelerator is applied, then recovers. Which area should be investigated first?

  1. The fuel supply and delivery pressure, including filters and lift pump Correct answer.
  2. The seat suspension
  3. The windscreen wiper motor
  4. The headlamp alignment

Explanation

Power surging under acceleration points to a fuel delivery problem such as a restricted filter, air ingress or weak lift pump causing pressure fluctuation. Electrical and body items do not influence engine power delivery in this pattern.

Question 37Heavy Vehicle Mechanic (craft apprenticeship curriculum)

Why is it important to use a calibrated torque wrench and follow the manufacturer's torque sequence when tightening a cylinder head?

  1. To achieve even clamping force that prevents head gasket failure and distortion of the head Correct answer.
  2. To make the bolts easier to remove next time
  3. To reduce the amount of gasket sealant required
  4. To increase the engine's compression ratio

Explanation

Cylinder head bolts must be tightened in stages and in the specified sequence so clamping load is distributed evenly, preventing gasket leakage and head warping. Correct torque does not change compression ratio or sealant needs.

Question 38Heavy Vehicle Mechanic (craft apprenticeship curriculum)

A mechanic is checking a heavy vehicle's air brake system for leaks with the engine off and reservoirs charged. The pressure drops steadily at the service brake valves. Which component is the most likely source?

  1. The park brake release valve spring
  2. The service brake valve or a leaking line in the service circuit Correct answer.
  3. The compressor discharge line
  4. The engine coolant thermostat

Explanation

A steady pressure loss at the service brake valves indicates leakage in the service circuit, such as a faulty valve or line, because that circuit is pressurised during application. Compressor and coolant components belong to different systems.

Question 39Heavy Vehicle Mechanic (craft apprenticeship curriculum)

What is the correct method for checking the condition of a heavy vehicle's shock absorbers during a workshop inspection?

  1. Measure the shock absorber's electrical resistance
  2. Look only for oil on the outside of the shock absorber body
  3. Test by compressing the shock absorber by hand and counting the seconds
  4. Check for fluid leakage, mount condition, and observe vehicle behaviour over a road test Correct answer.

Explanation

Shock absorber condition is assessed by inspecting for fluid leaks, damaged mounts and bushes, and confirming damping behaviour during a road test. Hand compression and electrical tests are not valid for hydraulic shock absorbers.

Question 40Heavy Vehicle Mechanic (craft apprenticeship curriculum)

A heavy vehicle's diesel engine has a cold-start problem and white smoke on start-up that clears after a few minutes. Which component is the most likely cause?

  1. The fuel tank breather
  2. The glow plugs or intake air pre-heater circuit Correct answer.
  3. The differential lock switch
  4. The exhaust brake butterfly valve

Explanation

Cold-start white smoke that clears as the engine warms suggests incomplete combustion from inadequate pre-heating, pointing to glow plugs or the intake air heater circuit. The other components do not affect cold combustion quality.

Question 41Heavy Vehicle Mechanic (craft apprenticeship curriculum)

A heavy vehicle's steering wheel has excessive free play before the road wheels begin to turn. Which inspection is the most appropriate first step?

  1. Increase tyre pressure on the steer axle
  2. Replace the steering gearbox immediately
  3. Check the steering column joints, drag link and tie rod ends for wear and adjustment Correct answer.
  4. Adjust the wheel alignment without inspection

Explanation

Excessive free play is diagnosed by tracing wear through the steering linkage, including column joints, drag link and tie rod ends, before condemning major components. Alignment and tyre pressure do not cause free play.

Question 42Heavy Vehicle Mechanic (craft apprenticeship curriculum)

Why must a heavy vehicle's wheel nuts be re-torqued after a wheel has been refitted and the vehicle driven a short distance?

  1. Because seating of the wheel and nut faces can relax the clamping force, and re-torquing restores it Correct answer.
  2. To check the brake pad thickness
  3. To rotate the tyre to a new position on the rim
  4. To allow the tyre to cool before inflation

Explanation

During initial operation, paint, dirt and surface irregularities between the wheel and hub can settle, reducing nut preload and risking loosening. Re-torquing to the specified value after the recommended distance restores correct clamping force.

Question 43Heavy Vehicle Mechanic (craft apprenticeship curriculum)

What is the function of a heavy vehicle's exhaust gas recirculation (EGR) valve?

  1. To cool the engine coolant
  2. To recirculate a portion of exhaust gas into the intake to lower combustion temperature and reduce nitrogen oxide emissions Correct answer.
  3. To increase turbocharger boost pressure
  4. To increase fuel pressure at the injectors

Explanation

EGR reduces peak combustion temperatures by diluting the intake charge with inert exhaust gas, which suppresses nitrogen oxide formation. It does not boost pressure, cool coolant or raise fuel pressure.

Question 44Heavy Vehicle Mechanic (craft apprenticeship curriculum)

A heavy vehicle's automatic transmission has harsh engagement when selecting drive from neutral. Which factor is most likely to cause this condition?

  1. Incorrect transmission fluid level or pressure, or a faulty pressure control solenoid Correct answer.
  2. Worn brake linings
  3. Low engine oil level
  4. A loose wheel nut

Explanation

Harsh engagement is typically caused by incorrect fluid level or line pressure, or a sticking or faulty pressure control solenoid affecting clutch apply. Engine oil and brake components do not control transmission engagement quality.

Question 45Heavy Vehicle Mechanic (craft apprenticeship curriculum)

A heavy vehicle mechanic is diagnosing a fault where the engine derates and logs a high exhaust gas temperature code under load. Which factor should be investigated first?

  1. The windscreen washer pump
  2. A restricted charge air cooler or faulty intake air temperature sensor causing high combustion temperatures Correct answer.
  3. The radio antenna
  4. The door lock actuator

Explanation

High exhaust gas temperature under load commonly results from restricted charge air cooling or an inaccurate intake air temperature signal, which raises combustion temperature. The other options are body electrical items with no effect on combustion.

Question 46Heavy Vehicle Mechanic (craft apprenticeship curriculum)

A heavy vehicle has a front tyre worn heavily on the inner shoulder only. Which alignment condition is most consistent with this wear pattern?

  1. Correct caster angle
  2. Excessive positive camber
  3. Excessive negative camber or incorrect toe setting Correct answer.
  4. Over-inflation of the tyre

Explanation

Inner shoulder wear is associated with excessive negative camber or a toe fault that drags the inner edge across the road. Over-inflation causes centre wear, and positive camber would wear the outer shoulder.

Question 47Heavy Vehicle Mechanic (craft apprenticeship curriculum)

A mechanic is investigating a heavy vehicle that pulls to one side during braking. After confirming tyre pressures and wheel bearings are correct, which check is most appropriate next?

  1. Adjust the headlights
  2. Change the engine oil
  3. Inspect brake linings, drums and air brake valve operation for uneven application on each side Correct answer.
  4. Replace the steering wheel

Explanation

Once tyre and bearing factors are ruled out, uneven braking force from worn linings, distorted drums or a faulty brake valve on one side is the likely cause of pull. Engine and lighting items do not affect brake balance.

Question 48Heavy Vehicle Mechanic (craft apprenticeship curriculum)

A heavy vehicle's engine coolant temperature rises rapidly and the radiator top hose is firm and hot while the bottom hose remains cool. Which component is the most likely cause?

  1. A blocked windscreen washer jet
  2. A stuck-open thermostat
  3. A faulty radiator cap seal only
  4. A stuck-closed thermostat preventing coolant circulation to the radiator Correct answer.

Explanation

A thermostat stuck closed stops coolant flow to the radiator, so the top hose becomes hot from the engine side while the radiator and bottom hose stay cool. A stuck-open thermostat would cause slow warm-up, not rapid overheating.

Question 49Heavy Vehicle Mechanic (craft apprenticeship curriculum)

A mechanic is asked to verify that a heavy vehicle's spring brake chambers will release correctly. Which check is most relevant to safety?

  1. Confirm the spring brake releases fully with air applied and that the pushrod stroke is within specification Correct answer.
  2. Inspect the chamber's mounting bracket for cosmetic rust only
  3. Check the colour of the air line fittings
  4. Measure the chamber's external paint thickness

Explanation

Spring brake chambers store high energy, so the critical check is that they release fully when air is applied and that pushrod stroke is within the manufacturer's limit. Stroke outside specification indicates adjustment or chamber problems that affect braking.

Question 50Heavy Vehicle Mechanic (craft apprenticeship curriculum)

Why is it necessary to use a torque wrench with the correct drive size and calibration when tightening suspension U-bolts on a heavy vehicle?

  1. To make the bolts look uniform
  2. To reduce the vehicle's tare mass
  3. To change the spring rate
  4. To achieve the specified clamping force so the spring pack does not shift, while avoiding over-torque that can stretch or break the U-bolt Correct answer.

Explanation

U-bolts must clamp the spring pack with the specified force; under-torque allows the axle to shift, while over-torque stretches or fractures the stud. Correct tool size and calibration ensure the setting is achieved accurately.