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Construction Plant Fitting practice questions

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Question 1Construction plant fitting

When setting up a mobile crane on a construction site, which factor most directly determines the crane's actual lifting capacity at a given radius?

  1. The engine oil pressure at idle
  2. The colour of the load being lifted
  3. The number of workers available to guide the load
  4. The load chart configuration for the boom length, radius, and outrigger setup in use Correct answer.

Explanation

A crane's rated capacity is read from the manufacturer's load chart and depends on boom length, working radius, counterweight, and whether the crane is on outriggers or tyres. Any configuration change alters the allowable load. Engine condition and personnel numbers do not change the structural or stability limits.

Question 2Construction plant fitting

A hydraulic excavator's track tension is set too tight. Which wear or damage outcome is most likely?

  1. Accelerated seal and pin/bushing wear and increased risk of track component failure Correct answer.
  2. Reduced hydraulic oil temperature during digging
  3. Faster bucket cycle times with no wear penalty
  4. Improved fuel economy with no side effects

Explanation

Over-tensioned tracks load the pins, bushings, idlers and final drive seals beyond design limits, causing accelerated wear and possible cracking. Correct tension allows slight sag as specified by the manufacturer. Fuel economy and cycle times are not improved by over-tensioning.

Question 3Construction plant fitting

In a hydraulic system on a construction machine, what is the primary function of a relief valve?

  1. To cool the hydraulic fluid before it re-enters the reservoir
  2. To limit maximum system pressure by diverting flow back to tank Correct answer.
  3. To filter contaminants from the return oil
  4. To increase pump displacement at high load

Explanation

A relief valve opens at its set pressure and bypasses flow to the tank, protecting components from over-pressure. It is a pressure-limiting device, not a filter, cooler, or displacement control. Pump displacement is governed by the pump's own controls.

Question 4Construction plant fitting

Before welding a repair patch onto a loader bucket in the field, which safety step is most important regarding the machine's electronics?

  1. Increase the alternator output to stabilise the arc
  2. Disconnect the battery and unplug or isolate the machine ECU to protect it from welding current Correct answer.
  3. Run the engine at high idle to cool the bucket
  4. Remove the bucket teeth to reduce weight

Explanation

Welding current can travel through the machine frame and damage the ECU, sensors, and wiring. The earth clamp should be placed close to the weld and electronics isolated by disconnecting the battery and unplugging controllers. Engine speed and bucket teeth are unrelated to electrical protection.

Question 5Construction plant fitting

Which component in a diesel engine's fuel system removes large particulate contamination before the fuel reaches the high-pressure pump?

  1. Primary (pre-) fuel filter or water separator Correct answer.
  2. Exhaust gas recirculation valve
  3. Turbocharger compressor wheel
  4. Intercooler core

Explanation

The primary filter or water separator traps coarse particles and water before the lift pump and high-pressure pump, protecting them from wear. The turbocharger, EGR valve and intercooler are air-path components and do not filter fuel.

Question 6Construction plant fitting

A wheel loader's brake pedal feels spongy and travels further than normal. Which fault is most consistent with these symptoms?

  1. A seized park brake caliper
  2. Low engine coolant level
  3. Air in the hydraulic brake circuit Correct answer.
  4. Worn tyre tread depth

Explanation

Air is compressible, so trapped air in the brake hydraulic circuit causes a spongy pedal and increased travel. A seized caliper usually causes drag or heat, not a spongy pedal. Tyre wear and coolant level do not affect pedal feel.

Question 7Construction plant fitting

What is the purpose of a torque converter in a powershift transmission on a wheel loader?

  1. To mechanically lock the axles during braking
  2. To filter transmission oil before the cooler
  3. To multiply engine torque and allow a fluid coupling between engine and transmission Correct answer.
  4. To provide steering assist at low speed

Explanation

A torque converter uses fluid flow between an impeller and turbine to multiply torque at low speed and provide a smooth, slip-based coupling. It does not lock axles, filter oil, or provide steering assist. These are functions of other systems.

Question 8Construction plant fitting

During a daily walk-around inspection of an excavator, which finding should stop the machine from being operated until corrected?

  1. A loose radio antenna mount
  2. A cracked hydraulic hose weeping oil near the boom Correct answer.
  3. A slightly dusty cab floor mat
  4. A small paint chip on the counterweight

Explanation

A cracked, weeping hydraulic hose can fail suddenly under pressure, causing loss of control or injection injury, so the machine must be stopped. Cosmetic issues and cab cleanliness do not present an immediate safety hazard.

Question 9Construction plant fitting

A telescopic handler's load moment indicator (LMI) alarms during a lift. What is the correct operator response?

  1. Stop and reduce the load or radius until the LMI returns within the safe zone Correct answer.
  2. Increase engine speed to lift through the alarm
  3. Continue slowly because the alarm is only advisory
  4. Extend the boom further to lower the load quickly

Explanation

The LMI warns that the machine is approaching or exceeding its rated capacity for the current radius. The operator must reduce load or radius to restore a safe margin. Continuing, revving harder, or extending the boom worsens the overload condition.

Question 10Construction plant fitting

A hydraulic cylinder on a backhoe drifts slowly under load when the control valve is in neutral. Which cause is most probable?

  1. A blocked suction strainer
  2. A worn bucket cutting edge
  3. Internal leakage past the piston seal or a leaking load-holding valve Correct answer.
  4. Incorrect engine valve clearance

Explanation

Drift with the valve centred indicates internal bypass, typically past a worn piston seal or through a faulty load-holding/check valve. A blocked suction strainer causes cavitation and poor performance, not drift. Bucket edge wear and valve clearance are unrelated.

Question 11Construction plant fitting

When pressure-testing a hydraulic circuit, where should the test gauge be connected to read the main relief setting?

  1. At the pilot line to the joystick
  2. At the pressure test port downstream of the pump, before the relief valve Correct answer.
  3. At the breather on top of the reservoir
  4. At the return filter housing outlet

Explanation

The main relief setting is measured at the pump discharge test port, where the gauge sees full system pressure before the relief diverts flow. Return lines, breathers, and pilot lines show lower or different pressures and cannot confirm the main relief setting.

Question 12Construction plant fitting

A machine's final drive is making a rhythmic whining noise that increases with travel speed. Which diagnostic step is most appropriate first?

  1. Re-torque the wheel nuts
  2. Check the final drive oil level and inspect the drained oil for metal particles Correct answer.
  3. Adjust the engine idle speed
  4. Replace the hydraulic pump immediately

Explanation

Noise that rises with travel speed points to the final drive or its bearings and gears. Checking oil level and inspecting drained oil for metal gives direct evidence of internal wear before any replacement. Pump replacement, idle adjustment, and wheel nut torque do not address final drive noise.

Question 13Construction plant fitting

Why must a diesel particulate filter (DPF) regeneration cycle be completed before shutting down a machine that has entered active regeneration?

  1. Interrupting regeneration can leave excessive soot and fuel residue that damages the filter and dilutes engine oil Correct answer.
  2. It ensures the coolant reaches operating temperature
  3. It prevents the battery from discharging during the next shift
  4. It resets the hour meter to zero

Explanation

Active regeneration raises exhaust temperature to burn off soot; interrupting it can leave unburnt fuel and soot in the filter and allow fuel to enter the oil sump. The other options describe unrelated systems and effects.

Question 14Construction plant fitting

A hydraulic excavator's swing function is slow in both directions while all other functions are normal. Which area should be investigated first?

  1. The travel motor final drives
  2. The bucket cylinder and its seals
  3. The swing motor, swing relief valves and swing brake release circuit Correct answer.
  4. The engine air filter restriction indicator

Explanation

When only the swing function is slow, the fault is localised to the swing circuit: swing motor condition, swing relief settings, or the swing brake not fully releasing. Bucket cylinder, air filter, and travel drives affect other functions and would not isolate to swing alone.

Question 15Construction plant fitting

What is the correct procedure for checking the oil level in a powershift transmission?

  1. With the engine off and the machine on a slope
  2. Immediately after a cold start with the engine at full throttle
  3. Only after draining the transmission completely
  4. With the engine running at idle and the transmission in neutral at operating temperature, as specified by the manufacturer Correct answer.

Explanation

Transmission oil level is normally checked with the engine idling in neutral at operating temperature so the converter and galleries are filled and the dipstick reads correctly. Checking cold, on a slope, or after draining gives false readings.

Question 16Construction plant fitting

A hydraulic quick-coupler on an excavator fails to lock a bucket securely. What is the most serious consequence if the machine is operated?

  1. The tracks will lose tension
  2. The hydraulic oil will overheat rapidly
  3. The attachment can detach unexpectedly and strike workers or equipment Correct answer.
  4. The engine will derate to idle

Explanation

A quick-coupler that does not lock properly can release the attachment under load, creating a severe struck-by and crush hazard. Oil overheating, engine derate, and track tension are unrelated to coupler locking.

Question 17Construction plant fitting

Which measurement best indicates whether a hydraulic pump is worn internally?

  1. Measuring tyre inflation pressure
  2. Measuring the alternator charging voltage
  3. Comparing case drain flow against the manufacturer's maximum allowable at rated pressure and temperature Correct answer.
  4. Checking the engine coolant pH

Explanation

Case drain flow rises as internal clearances in a pump wear, so comparing it with the manufacturer's limit at rated conditions is a standard wear indicator. Voltage, coolant pH, and tyre pressure say nothing about pump internal leakage.

Question 18Construction plant fitting

A track-type dozer is pulling to one side during straight travel. Which combination of checks is most relevant?

  1. Track tension on both sides, steering clutch/brake adjustment, and final drive condition Correct answer.
  2. Bucket tooth wear and cutting edge straightness
  3. Cab air filter and seat suspension
  4. Engine oil viscosity and coolant concentration

Explanation

Uneven track tension, a dragging steering clutch or brake, or a failing final drive on one side will cause the machine to pull. Engine oil, coolant, bucket teeth, and cab items do not affect straight-line tracking.

Question 19Construction plant fitting

When torqueing cylinder head bolts on a diesel engine, why is a torque-plus-angle method often specified instead of a single torque figure?

  1. It reduces the number of bolts required
  2. It allows the bolts to be reused indefinitely without inspection
  3. It produces a more consistent clamp load by stretching the bolt into its elastic range beyond the yield point of friction variation Correct answer.
  4. It eliminates the need for a calibrated torque wrench

Explanation

Torque-plus-angle tightens the bolt a set rotation after a low seating torque, so clamp load depends mainly on thread pitch rather than friction, giving more consistent stretch. It does not permit unlimited reuse, remove the need for calibration, or change bolt count.

Question 20Construction plant fitting

A wheel loader's hydraulic oil overheats only when the machine is working hard with the bucket, while temperatures are normal during roading. Which cause is most likely?

  1. A clogged cab air filter
  2. Excessive internal leakage or a relief valve lifting under heavy working load Correct answer.
  3. Low tyre pressure on the front axle
  4. A faulty thermostat in the engine cooling system

Explanation

Heat generated only under heavy hydraulic work points to energy being lost as pressure drop through internal leakage or a relief valve that lifts too early. Engine thermostat, tyre pressure and cab filtration would not produce load-specific hydraulic overheating.

Question 21Construction plant fitting

A hydraulic excavator exhibits slow cycle times across all functions, and a flow test shows pump output well below specification while pressure is normal at deadhead. Which conclusion is best supported?

  1. The relief valve is set too low
  2. The cylinders are bypassing internally
  3. The return filter is bypassed
  4. The pump is delivering insufficient flow, indicating internal wear or a faulty pump control Correct answer.

Explanation

Normal deadhead pressure shows the relief is capable of holding pressure, but low measured flow across all functions indicates the pump cannot deliver its rated volume, consistent with wear or a control fault. A low relief setting would show low deadhead pressure, and cylinder bypass would affect individual functions.

Question 22Construction plant fitting

During a lift with a crawler crane on soft ground, the operator notices the machine beginning to settle on one side. What is the technically correct immediate action?

  1. Increase counterweight by adding site materials to the rear deck
  2. Slew quickly to the firm side while holding the load
  3. Raise the load higher to reduce ground pressure
  4. Lower the load to the ground, stop the lift, and reassess ground bearing and matting before continuing Correct answer.

Explanation

Settlement indicates the ground bearing capacity is being exceeded and stability is compromised. The load must be grounded and the lift stopped before reassessing with proper matting or a new position. Raising the load, slewing with load, or adding unapproved counterweight worsens the hazard.

Question 23Construction plant fitting

A machine's engine ECM logs repeated injector circuit faults on one cylinder after a harness repair. Which diagnostic approach is most rigorous?

  1. Increase fuel rail pressure to compensate
  2. Clear the fault codes and return the machine to service
  3. Measure injector solenoid resistance and check harness continuity and insulation under load, comparing with the manufacturer's values Correct answer.
  4. Replace all injectors without testing the harness

Explanation

Repeated circuit faults after harness work suggest a resistance, continuity or insulation problem that may only appear under vibration or load. Measuring solenoid resistance and checking the harness against specification isolates the fault. Blind replacement, pressure changes, or clearing codes without diagnosis risks recurrence.

Question 24Construction plant fitting

A hydraulic system uses a load-sensing variable-displacement pump. The machine is sluggish and the pump stays at high displacement with high standby pressure. Which fault best explains this behaviour?

  1. The bucket is fitted with new teeth
  2. The load-sensing line is blocked or leaking, so the pump control does not receive the demand signal Correct answer.
  3. The oil cooler fan is running
  4. The return filter is new

Explanation

In a load-sensing system the pump destrokes when no demand signal reaches the control. A blocked or leaking sensing line leaves the pump at high displacement and raises standby pressure, causing sluggish, hot operation. New filters, a running fan, and new teeth do not affect the sensing signal.

Question 25Construction plant fitting

A dozer's transmission oil shows a milky, emulsified appearance after several weeks of operation. Which combination of causes should be investigated?

  1. Incorrect tyre inflation and wheel alignment
  2. Water ingress through a failed cooler, breather, or seal, combined with oil aeration from a low level or wrong oil Correct answer.
  3. Worn track shoes and loose sprocket bolts
  4. Excessive engine coolant temperature only

Explanation

Milky transmission oil indicates water contamination and/or aeration. Failed oil coolers, damaged breathers, or seals admit water, while low oil level or incorrect oil causes foaming. Engine temperature alone, undercarriage wear, and tyre issues do not emulsify transmission oil.

Question 26Construction plant fitting

On a construction machine, what does the undercarriage track shoe gauge primarily determine?

  1. The grade and hardness of the track link steel
  2. The wear limit for the grouser height and link wear
  3. The load rating of the final drive bearings
  4. The correct tension setting for the track chain Correct answer.

Explanation

A track shoe gauge is a measuring tool used to set and verify track chain tension, usually by measuring the sag between the sprocket and the front idler. Correct tension prevents derailing and reduces wear on pins, bushings, and the idler. Grouser height and link wear are measured with separate wear gauges, not the tension gauge.

Question 27Construction plant fitting

Which component protects a hydraulic system from a sudden pressure spike caused by a shock load on a cylinder?

  1. The main relief valve Correct answer.
  2. The breather on the reservoir
  3. The return filter element
  4. The pilot-operated check valve

Explanation

The main relief valve opens when circuit pressure exceeds its setting, dumping flow to tank and capping the peak pressure. This protects hoses, seals, and structural components from shock loads. Filters and breathers do not limit pressure, and a pilot check valve holds load but does not relieve overpressure.

Question 28Construction plant fitting

A diesel engine in a wheel loader cranks slowly and the battery terminals are clean and tight. Which test is the most direct next step?

  1. Replace the starter motor immediately
  2. Inspect the air filter restriction indicator
  3. Measure battery voltage while cranking and check the voltage drop across the starter cables Correct answer.
  4. Check the engine oil pressure with a mechanical gauge

Explanation

Slow cranking with clean terminals usually indicates a battery that cannot supply cranking current or excessive resistance in the starter circuit. Measuring cranking voltage and voltage drop across the cables isolates the battery from the cables and starter. Replacing parts before testing wastes money and may not fix the fault.

Question 29Construction plant fitting

Which practice is correct when storing a hydraulic excavator's boom and attachment overnight on a site?

  1. Rest the bucket on a stack of pallets to keep it clean
  2. Park with the arm fully extended and the bucket in the air
  3. Leave the boom raised with the engine off to save cycle time
  4. Lower the attachment to the ground and apply the safety lock lever Correct answer.

Explanation

Lowering the attachment removes stored hydraulic and gravitational energy, and the safety lock lever prevents accidental control movement. Leaving the boom raised relies on valve sealing and creates a crush hazard if pressure bleeds off. Parking on pallets is unstable and not an approved practice.

Question 30Construction plant fitting

What is the main function of a final drive in a crawler excavator's travel circuit?

  1. To filter contamination from the travel motor oil
  2. To cool the hydraulic oil returning from the travel motor
  3. To limit the maximum travel speed electronically
  4. To reduce motor speed and multiply torque to the sprocket Correct answer.

Explanation

A final drive is a planetary gear reduction that converts the high-speed, low-torque output of the travel motor into low-speed, high-torque rotation of the track sprocket. It is not a filter, cooler, or speed limiter. The reduction is what gives the machine the tractive effort to move under load.

Question 31Construction plant fitting

Which item on a telehandler should be checked before raising a load with the boom?

  1. The engine coolant colour
  2. The frame level indicator and the tyre condition and pressure Correct answer.
  3. The horn volume
  4. The seat fabric condition

Explanation

A telehandler's stability depends on the machine being level and the tyres being correctly inflated and undamaged. The frame level indicator confirms the chassis is level, and tyre condition affects load capacity and lateral stability. Coolant colour, horn volume, and seat condition have no bearing on lift stability.

Question 32Construction plant fitting

What is the purpose of a grease fitting on a pivot pin of a loader linkage?

  1. To introduce lubricant into the bearing clearance Correct answer.
  2. To lock the pin against rotation
  3. To allow hydraulic oil to drain from the pin
  4. To vent air from the hydraulic cylinder

Explanation

A grease fitting lets the operator inject lubricant into the clearance between the pin and bushing, reducing friction and wear. Grease also displaces contaminants and helps seal the joint. It does not drain hydraulic oil, vent cylinders, or lock the pin.

Question 33Construction plant fitting

A machine's hour meter shows 500 hours but the oil change interval is 250 hours. What does this indicate for maintenance planning?

  1. The oil change is overdue and should be performed before further use Correct answer.
  2. The interval only applies to machines over 1000 hours
  3. The oil has been changed twice as often as required
  4. The hour meter is faulty and should be replaced

Explanation

If the service interval is 250 hours and the meter reads 500, the scheduled oil change is overdue and should be completed before the machine continues working. Deferring it accelerates wear and may void warranty coverage. The meter reading does not by itself indicate a meter fault or an exemption.

Question 34Construction plant fitting

A hydraulic cylinder seal is leaking oil past the rod wiper. Which consequence most directly affects machine performance?

  1. The cylinder will extend faster than normal
  2. The hydraulic oil will become more viscous
  3. The circuit will lose pressure and the rod will drift under load Correct answer.
  4. The return filter will bypass

Explanation

A failed rod seal allows pressurized oil to escape past the piston rod, so the cylinder cannot hold pressure and the load drifts. It also contaminates the exterior and wastes oil. Leakage does not make the cylinder extend faster or change oil viscosity directly.

Question 35Construction plant fitting

During a hydraulic flow test, the pump delivers rated flow at low pressure but flow falls sharply as pressure rises. What does this pattern suggest?

  1. The pump is internally worn and bypassing oil Correct answer.
  2. The suction strainer is blocked
  3. The relief valve is set too low
  4. The oil level is too high

Explanation

A pump that produces rated flow at low pressure but loses flow as pressure increases is typically worn internally, allowing oil to bypass across clearances. A low relief setting would cap pressure but not cause flow to fall progressively. A blocked suction strainer would reduce flow at all pressures and often cause cavitation noise.

Question 36Construction plant fitting

A wheel loader's torque converter is overheating during load-and-carry cycles. Which operating practice most reduces heat generation?

  1. Using the torque converter as a clutch during long pushes
  2. Keeping the transmission in a higher gear during loading
  3. Reducing converter slip by matching gear and throttle to the load Correct answer.
  4. Holding the machine against a pile with the bucket stalled

Explanation

Torque converter heat is generated by slip between the impeller and turbine. Matching gear and throttle to the load reduces slip and keeps the converter closer to its efficient coupling point. Stalling the bucket against a pile or using the converter as a clutch greatly increases slip and heat.

Question 37Construction plant fitting

An excavator's hydraulic oil temperature rises only when the machine is working hard, while it stays normal at idle. Which check is most relevant first?

  1. The track chain tension
  2. The engine valve clearance
  3. The hydraulic oil cooler and fan drive for airflow and cleanliness Correct answer.
  4. The battery charging voltage

Explanation

Heat that appears only under heavy work points to insufficient heat rejection, so the oil cooler and its fan drive are the first items to check. A restricted or dirty cooler, or a slipping fan, cannot remove the heat generated during high-flow work. Charging voltage, valve clearance, and track tension do not explain load-dependent oil heating.

Question 38Construction plant fitting

A track-type dozer veers to the left during straight travel. Which check is most appropriate first?

  1. Adjust the bucket cutting edge
  2. Inspect the left final drive for oil leaks and the left steering clutch or brake for adjustment Correct answer.
  3. Check the engine air filter restriction
  4. Replace both track chains

Explanation

Veering to one side usually indicates unequal drive effort, such as a slipping steering clutch or brake or a dragging final drive on the affected side. Checking the left final drive and steering components isolates the cause before replacing parts. Track chains, air filters, and cutting edges do not explain a consistent directional pull.

Question 39Construction plant fitting

A hydraulic quick-coupler on an excavator does not fully engage its locking pin. What is the correct action?

  1. Lower the attachment, relieve pressure, and inspect the coupler mechanism before use Correct answer.
  2. Operate slowly and monitor the attachment
  3. Tap the pin with a hammer while the attachment is raised
  4. Increase hydraulic pressure at the relief valve to force engagement

Explanation

An incompletely engaged coupler can release the attachment under load, so the machine must be shut down safely before inspection. Lowering the attachment and relieving pressure removes stored energy and allows a proper inspection of the locking mechanism. Operating with a known fault or forcing engagement risks a dropped bucket.

Question 40Construction plant fitting

Why is a torque-plus-angle tightening method used for cylinder head bolts on a diesel engine?

  1. To reduce the number of bolts required
  2. To produce a consistent clamp load by stretching the bolt into its elastic range beyond yield Correct answer.
  3. To eliminate the need for a head gasket
  4. To allow reuse of torque-to-yield bolts

Explanation

Torque-plus-angle tightening rotates the bolt a set angle after an initial torque, producing a more consistent clamp load because friction variation during torquing is largely overcome. The bolt is stretched into its elastic or yield range, giving uniform gasket sealing. It does not reduce bolt count, allow reuse of torque-to-yield bolts, or eliminate the gasket.

Question 41Construction plant fitting

A telescopic handler's load moment indicator alarms during a lift. What is the correct operator response?

  1. Extend the boom to move the load closer to the ground
  2. Continue the lift slowly while watching the load
  3. Lower the load and reduce the load moment before continuing Correct answer.
  4. Increase engine speed to raise the boom faster

Explanation

The load moment indicator warns that the machine is approaching or exceeding its stability limit. The operator must stop, lower the load, and reduce the load moment by reducing radius or load weight. Continuing the lift or extending the boom increases the moment and the risk of tipping.

Question 42Construction plant fitting

A hydraulic system's return filter indicator shows the element is bypassing. What is the most likely effect on the machine?

  1. System pressure rises above relief setting
  2. Oil temperature falls rapidly
  3. Contaminants pass unfiltered back to the reservoir and circulate Correct answer.
  4. Pump output increases

Explanation

When a return filter bypasses, oil returns to the reservoir without passing through the element, so contaminants circulate and can damage pumps and valves. Bypassing does not increase pump output or raise pressure above the relief setting. It also does not reduce oil temperature.

Question 43Construction plant fitting

A machine's engine ECM logs repeated injector circuit faults on one cylinder after a harness repair. Which approach is most appropriate?

  1. Replace all injectors on the engine
  2. Increase the injector pulse width in software
  3. Inspect the repaired harness section for pin tension, chafing, and correct routing Correct answer.
  4. Replace the ECM immediately

Explanation

Faults recurring after a harness repair point to a problem in the repaired area, such as loose pin tension, chafing, or incorrect routing near heat or moving parts. Inspecting that section is the logical next step before replacing expensive components. Replacing the ECM or all injectors is premature without evidence.

Question 44Construction plant fitting

A load-sensing variable-displacement pump stays at high displacement while the machine is sluggish. Which area should be investigated?

  1. The track chain tension
  2. The engine coolant thermostat
  3. The seat suspension
  4. The load-sensing signal line and the pump compensator Correct answer.

Explanation

In a load-sensing system, the pump destrokes when the load-sensing signal tells it demand is low. If the pump stays at high displacement while the machine is sluggish, the signal line may be blocked or leaking, or the compensator may be stuck. Track tension, thermostat, and seat suspension do not affect pump displacement control.

Question 45Construction plant fitting

A dozer's transmission oil appears milky and emulsified after weeks of operation. Which combination of causes is most likely?

  1. Overfilling with the correct oil grade
  2. Water ingress through the breather or a leaking cooler, combined with aeration Correct answer.
  3. Using a higher viscosity oil than specified
  4. Normal oil oxidation at operating temperature

Explanation

Milky, emulsified oil indicates water or air mixed with the oil. Water can enter through the breather, a leaking transmission cooler, or condensation, while aeration from a suction leak also produces foam. Overfilling, normal oxidation, or a higher viscosity grade do not produce a milky emulsion.

Question 46Construction plant fitting

A crawler crane begins to settle on one side during a lift on soft ground. What is the correct immediate action?

  1. Continue the lift quickly to finish before further settlement
  2. Lower the load, stop the lift, and reposition or improve the ground support Correct answer.
  3. Increase counterweight to balance the machine
  4. Raise the boom to reduce ground pressure

Explanation

Settlement during a lift signals that the ground bearing capacity is inadequate and a tip-over may be developing. The load must be lowered and the lift stopped, then the machine repositioned or the ground improved with mats or a prepared pad. Continuing the lift or adding counterweight increases risk.

Question 47Construction plant fitting

A hydraulic excavator's swing function is slow in both directions while all other functions are normal. Which area should be checked first?

  1. The main pump output at all functions
  2. The bucket cylinder seals
  3. The swing motor, swing reduction, and swing relief valves Correct answer.
  4. The engine air filter

Explanation

If only swing is slow in both directions, the fault is isolated to the swing circuit: the swing motor, swing reduction gearbox, or the swing relief and brake valves. Main pump output would affect all functions, and the air filter or bucket seals are unrelated. Isolating the affected circuit narrows diagnosis efficiently.

Question 48Construction plant fitting

A machine's diesel particulate filter repeatedly enters regeneration and then derates shortly after. Which underlying fault is most consistent with this pattern?

  1. An incorrectly adjusted seat switch
  2. A faulty coolant temperature sensor reading low
  3. A leaking intake manifold gasket causing excess soot loading Correct answer.
  4. A worn bucket cutting edge

Explanation

Repeated regeneration followed by derate indicates the filter is loading with soot faster than it can regenerate. Excess soot can come from incomplete combustion or oil consumption, such as a leaking intake gasket, worn injectors, or turbo seals. A low coolant reading, cutting edge wear, or a seat switch do not generate soot.

Question 49Construction plant fitting

A hydraulic cylinder drifts slowly under load when the control valve is in neutral. Which cause is most probable?

  1. Low engine idle speed
  2. A clogged return filter
  3. Internal leakage past the piston seal or a worn control valve spool Correct answer.
  4. A loose fan belt

Explanation

Drift in neutral means oil is escaping from the loaded side of the cylinder. This occurs through internal leakage past the piston seal or past a worn valve spool. A clogged return filter, low idle, or a loose fan belt do not allow the cylinder to creep under load with the valve centred.

Question 50Construction plant fitting

When setting up a hydraulic torque wrench to tighten a track shoe bolt, which specification should be used to determine the applied torque?

  1. The torque value specified in the machine's service manual for that fastener Correct answer.
  2. The breakaway torque measured when loosening the old bolt
  3. The torque achieved by the previous bolt tightened in the same sequence
  4. The maximum torque the wrench can produce at full pump pressure

Explanation

Fastener torque must always come from the manufacturer's specification for that joint, because it reflects bolt grade, thread condition, and the designed clamp load. Tool capacity or observed values from old or neighbouring bolts are not valid substitutes.