Cooling and Lubrication Lesson Test (40 Questions)

Answer: C

Correct answer: Opens and closes to control coolant flow to the radiator. The thermostat is a temperature-controlled valve. It stays closed while the engine is cold so the engine warms quickly, then opens near its rated temperature to let coolant flow to the radiator. It does not pump or cool anything itself.

• A: Moving coolant is the job of the coolant pump; the thermostat is only a valve.
• B: Releasing heat to the air is the radiator's job, not the thermostat's.
• C (correct): Its wax pellet expands with heat and opens the valve, so it regulates how much coolant goes to the radiator.
• D: Holding pressure to raise the boiling point is what the pressure cap does.

Answer: A

Correct answer: Pass heat from hot coolant into the air flowing through it. Tubes, fins, and side tanks at the front of the vehicle describe the radiator. Hot coolant spreads through the tubes, and air moving across the fins carries the heat away.

• A (correct): The tubes and fins form a heat exchanger that sheds coolant heat into passing air; that is the radiator.
• B: The heater core warms the cabin, and it sits behind the dashboard, not at the front of the car.
• C: Filtering oil belongs to the oil filter in the lubrication system, not to a coolant heat exchanger.
• D: Holding expanded coolant is the job of the recovery or expansion tank, which has no tubes and fins.

Answer: C

Correct answer: Pressure raises the coolant boiling point so it resists turning to steam. As coolant warms and expands, the sealed system builds pressure held by the cap. Higher pressure raises the boiling point, roughly 3 degrees Fahrenheit for each psi, so the coolant stays liquid at higher temperatures.

• A: Freeze protection comes from the antifreeze mixture, not from cap pressure, which mainly affects boiling.
• B: The pump is driven by a belt, timing drive, or motor; system pressure does not speed it up.
• C (correct): Holding the system under pressure lets the coolant run hotter than its normal boiling point without boiling.
• D: Oil and coolant are kept apart by gaskets and walls, not by the radiator cap.

Answer: C

Correct answer: Capture contaminants carried in circulating oil. Oil picks up metal wear particles, carbon and dirt as it circulates, and those particles act like grinding grit on bearings and cylinder walls. The filter sits in the pressurized line after the pump, and its pleated media trap particles so cleaner oil reaches the parts. It does not create pressure or move oil, and it has no link to the coolant circuit. Replacing it at oil changes keeps the media from clogging.

• A: The radiator cap and the expansion of hot coolant set coolant pressure, not the oil filter.
• B: Engine torque and operating controls affect shaft speed; a filter does not accelerate it.
• C (correct): Correct: filter media remove many solid contaminants from the oil circuit.
• D: An oil filter handles only engine oil; it never injects coolant into the cylinders.

Answer: B

Correct answer: Coolant (water) pump. The coolant pump, often called the water pump, has an impeller that flings coolant outward and keeps it circulating through the engine and radiator. A closed loop still needs this pump to move coolant fast enough.

• A: The cap holds system pressure and lets expanded coolant out; it does not circulate anything.
• B (correct): Its spinning impeller pushes coolant through the jackets, to the radiator, and back again.
• C: The thermostat only opens or closes a path; it does not create flow.
• D: The oil pump moves engine oil from the sump to the bearings; it never handles coolant.

Answer: D

Correct answer: oil pan or sump. In a wet-sump design the pan bolted to the bottom of the engine is the reservoir: oil drains back into it by gravity, and a pickup tube near its bottom feeds the oil pump. That is why the dipstick reaches down into the pan and why the drain plug is located there. Dry-sump racing engines store oil in a separate tank instead. A radiator may look like a likely reservoir, but it holds coolant, not oil.

• A: A muffler quiets exhaust sound and does not store engine oil.
• B: A radiator normally carries engine coolant, not the main oil reservoir.
• C: An intake manifold routes air, not stored lubricating oil.
• D (correct): Correct: oil drains to and collects in the sump in a wet-sump engine.

Answer: A

Correct answer: Hot engine coolant. The heater core works like a small radiator. Hot coolant flows through it, and the blower pushes cabin air across its fins, so cabin heat depends on a warm engine and coolant reaching the core.

• A (correct): The heater core is part of the cooling system, and hot coolant from the engine passes through it.
• B: Refrigerant serves the A/C system for cooling, not the heater core.
• C: Exhaust leaves through the exhaust system and is never routed into the heater core.
• D: Oil stays in the lubrication circuit and does not run to the dashboard heater core.

Answer: B

Correct answer: Lubrication. Crankshaft bearings rely on a thin pressurized film of oil that keeps the journal floating on the bearing shell instead of rubbing metal against metal. The oil pump feeds that film through drilled passages called galleries, and the oil also carries away some heat. If pressure drops, the film collapses and the bearings can wear or seize quickly. Fuel injection may seem related because it also meters a fluid, but it handles fuel, not lubrication.

• A: Exhaust removes burned gases, not friction between bearings and journals.
• B (correct): Correct: engine oil helps separate moving parts to reduce friction and wear.
• C: Ignition initiates combustion but does not provide the oil film.
• D: Fuel injection meters fuel, not oil to crankshaft bearings.

Answer: D

Correct answer: Stop safely and follow the vehicle shutdown guidance. Oil pressure keeps a film between bearings and journals; without it, metal surfaces touch and can be ruined within minutes. Stopping in a safe place and shutting down limits that damage, after which oil level can be checked once the engine is off. Revving the engine to see if pressure recovers is tempting but makes parts spin faster with no protection. A normal temperature gauge does not help, because coolant and oil are separate systems.

• A: High-rpm running may worsen damage if oil delivery is inadequate.
• B: Normal coolant temperature does not prove safe lubrication pressure.
• C: The coolant cap is unrelated to engine-oil pressure and dangerous when hot.
• D (correct): Correct: a serious low-pressure warning can threaten bearings and requires prompt safe action.

Answer: D

Correct answer: Its resistance to flow. Viscosity means resistance to flow. Honey has high viscosity and water has low viscosity; engine oil must be thick enough to hold a film yet thin enough to flow quickly when cold.

• A: Color describes appearance, which says little about how readily the oil flows.
• B: Change intervals come from the manufacturer's schedule, not from a viscosity rating.
• C: Picking up moisture is a contamination issue, not a measure of viscosity.
• D (correct): Viscosity is how strongly a fluid resists flowing; thick oil has high viscosity.

Answer: B

Correct answer: A thermostat stuck open. An engine that will not reach operating temperature is losing too much heat to the radiator. A thermostat stuck open does exactly that, giving a low gauge reading, weak heat, and poorer fuel economy.

• A: A closed thermostat traps heat in the engine and causes overheating, not a cold-running engine.
• B (correct): A thermostat that never closes sends coolant to the radiator all the time, so the engine runs too cool and cabin heat stays weak.
• C: A blocked pickup starves the bearings of oil; it does not affect engine warm-up or cabin heat.
• D: A dead fan causes overheating at low speed; it would not keep the engine cold.

Answer: C

Correct answer: The electric cooling fan and its controls. At highway speed the car's own motion forces air through the radiator. At idle that ram air disappears and the fan carries the load, so overheating only at low speed points to the fan or its controls.

• A: A weak cap or seal could cause boil-over at any speed, not a fault that appears only at idle.
• B: The blend door only controls cabin heat; it does not affect engine cooling at idle.
• C (correct): At idle there is almost no ram air, so the fan must move air through the radiator; a fan fault shows up only at low speed.
• D: The relief valve limits oil pressure and has nothing to do with radiator airflow.

Answer: B

Correct answer: Coolant is getting into the engine oil. Glycol coolant mixed with oil gives a milky, milkshake-like look. Together with falling coolant level, it suggests an internal leak such as a failed head gasket, cracked head or block, or a leaking oil cooler, which needs diagnosis before more driving.

• A: Using a heavier grade would not make the oil milky or cause coolant loss.
• B (correct): Milky oil plus unexplained coolant loss points to coolant mixing with oil, for example through a head gasket, cracked head, or leaking oil cooler.
• C: A stuck-open thermostat makes the engine run cool; it does not move coolant into the oil.
• D: An open bypass lets unfiltered oil through but does not create a milky mixture.

Answer: C

Correct answer: Sump → oil pump → filter/galleries → moving parts → sump. Think of the loop as storage, pressure, cleaning, delivery and return. The pump draws oil from the pan through the pickup, pushes it through the filter into drilled galleries, and those passages feed the bearings, camshaft and valve train. Oil then drips or drains back to the pan to start again. Any route that passes through intake, exhaust, fuel or cooling parts mixes in a different system and cannot be the oil circuit.

• A: Intake and exhaust passages carry air and exhaust gas, not circulating engine oil.
• B: This mixes cooling, fuel and electrical components with no valid oil path.
• C (correct): Correct: oil is pumped from storage to lubricated components and returns by gravity.
• D: This mixes a fuel path and ignition components rather than an oil circuit.

Answer: A

Correct answer: 380 kJ. Use the heat equation with the given values.

• A (correct): Q = m c ΔT = 5 × 3.8 × 20 = 380 kJ.
• B: This multiplies only 3.8 × 20 and leaves out the 5 kg mass.
• C: This is ten times too large, a decimal slip when multiplying by 3.8.
• D: This multiplies only 5 × 20 and leaves out the specific heat.

Answer: C

Correct answer: Engine oil cooler. An oil cooler is a small heat exchanger: hot oil passes through tubes or plates while coolant or outside air flows across the other side and carries heat away. Engines that tow, run turbochargers or work hard often use one because oil that gets too hot thins out and breaks down faster. A cabin filter or vapor canister may look like an add-on part too, but neither exchanges heat with oil.

• A: A vapor canister handles fuel evaporation emissions, not oil heat rejection.
• B: Cabin filters clean ventilation air and do not cool lubricating oil.
• C (correct): Correct: an oil cooler transfers thermal energy away from circulating oil.
• D: A starter solenoid switches current to the starter and is not a heat exchanger.

Answer: D

Correct answer: The sudden pressure drop can make hot coolant flash to steam and spray out. A hot cooling system is under pressure, which keeps the coolant liquid above its normal boiling point. Removing the cap drops that pressure suddenly, so the coolant can flash to steam and spray out. Let the engine cool first.

• A: Opening the cap does not crack the tubes; the hazard is scalding coolant and steam.
• B: Oil and coolant stay in separate circuits; opening the cap does not force oil past the head gasket.
• C: Removing the cap has no effect on whether the thermostat opens or closes.
• D (correct): Releasing the pressure lowers the boiling point at once, so superheated coolant can boil instantly and scald.

Answer: D

Correct answer: Pressure in the lubrication circuit at the monitored location. An oil-pressure switch is a pressure-sensitive contact screwed into an oil gallery. When pressure at that point falls below a set threshold, the contacts close and light the warning. It does not measure how much oil is in the pan, its condition or anything about coolant; it reports only whether pressure is present where it is installed. A low oil level can trigger it indirectly by starving the pump, but the switch itself senses pressure.

• A: Washer fluid and engine antifreeze are unrelated, and neither is measured by an oil-pressure switch.
• B: Transmission-fluid color has no direct relationship to this engine-oil switch.
• C: Coolant concentration and freeze protection are not measured by an engine-oil pressure switch.
• D (correct): Correct: the instrument monitors the oil circuit pressure condition.

Answer: B

Correct answer: Oil behavior under specified low- and high-temperature viscosity tests. In a multigrade label the first number with W (winter) rates how the oil flows in cold-temperature tests, so a lower number means easier cold starts. The second number rates viscosity at normal operating temperature, about 100°C. Additives let one oil satisfy both ratings. The numbers are not temperatures in degrees and do not set change intervals, so reading 5W-30 as 5° and 30° is a common mistake.

• A: Service life must follow manufacturer and oil specifications, not numbers in the grade.
• B (correct): Correct: multigrade oil meets defined viscosity test ranges at different conditions.
• C: The grade numbers are viscosity ratings, not temperature limits or thermostat settings.
• D: Engine cylinders and valves are not encoded by engine-oil viscosity labels.

Answer: A

Correct answer: It captures contaminants rather than supplying pressure-producing flow. The pump, usually driven by the crankshaft or camshaft, is what actually moves oil; pressure builds because the bearings and passages resist that flow. The filter is a passive part that the oil passes through, trapping particles but adding no energy. You can reason this out from the parts themselves: a filter has no moving parts and no drive. Thinking a filter pushes oil is like thinking a coffee filter pours the coffee.

• A (correct): Correct: the pump supplies oil movement while the filter removes particles.
• B: Spark is produced by ignition components such as the coil and plugs, not by oil filtration.
• C: Oil filters belong to the lubrication system and are not mounted inside the radiator.
• D: Oil filters do not reverse crankshaft motion or engine timing.

Answer: D

Correct answer: Match the type on the label to the owner's manual specification. Coolant comes in many colors, and color is not a reliable guide to its chemistry. Reading the container label and matching the owner's manual specification avoids mixing types that could weaken corrosion protection.

• A: Water alone freezes, boils too easily, and lets metal rust; the system needs the specified mixture.
• B: Mixing types can reduce corrosion protection, so not every coolant is a safe match.
• C: Different chemistries can share a color, so matching color does not guarantee the same type.
• D (correct): Coolant color does not reliably identify its chemistry, so the label and the manual decide.

Answer: D

Correct answer: Forced convection. Convection is heat carried by a moving fluid. When a pump or fan moves the fluid, it is forced convection, which is the main way an engine's coolant carries heat to the radiator.

• A: Natural convection relies on warm fluid rising by itself; a pump is driving this flow.
• B: Radiation transfers heat by infrared waves with no fluid needed, which is not how coolant carries heat.
• C: Conduction moves heat through a solid without the material flowing; here the coolant itself travels.
• D (correct): Heat is carried by a moving fluid, and the pump drives the motion, which makes it forced convection.

Answer: A

Correct answer: Route excess oil back when pressure reaches a set limit. A positive-displacement oil pump moves more oil as rpm rises, and cold thick oil adds resistance. The relief valve opens at a set pressure and sends the extra oil back, protecting the filter, seals, and pump drive from excess pressure.

• A (correct): It opens at a preset pressure and returns extra oil to the pump inlet or sump, keeping pressure in a safe range.
• B: Holding oil in the filter is the anti-drainback valve's job, not the relief valve's.
• C: Bypassing a clogged filter is the filter bypass valve's job.
• D: The sump is not pressurized to raise a boiling point; that idea belongs to the coolant pressure cap.

Answer: C

Correct answer: 2.5 kW. Convert the time to seconds, then divide heat by time.

• A: This inverts the division, computing 60 ÷ 150.
• B: This divides by 1 without converting the minute to 60 seconds.
• C (correct): One minute is 60 s, and 150 kJ ÷ 60 s = 2.5 kJ/s, which is 2.5 kW.
• D: This multiplies by 60 instead of dividing by 60.

Answer: D

Correct answer: Conduction. Conduction is heat moving through a material by direct contact, as faster-vibrating particles pass energy to their neighbors. Hot combustion gas heats the inner cylinder wall, the metal conducts that heat outward, and coolant in the water jacket picks it up and carries it to the radiator. Combustion is the tempting answer because it makes the heat, but it is the source, not the way heat crosses the solid wall.

• A: Fuel injection supplies fuel and does not transmit heat through metal walls.
• B: Combustion creates much of the heat, not the wall-transfer mechanism.
• C: Braking converts motion into heat elsewhere and is not cylinder-wall heat transfer.
• D (correct): Correct: energy travels through the solid material by conduction.

Answer: B

Correct answer: Insufficient oil delivery to lubricated parts. The pickup is the inlet tube and screen that the pump draws from at the bottom of the pan. If sludge or debris blocks the screen, the pump cannot pull in enough oil, so pressure drops and the bearings and valve train may be starved. Symptoms include a flickering oil light or noisy lifters even when the dipstick shows a full pan. The pickup affects only lubrication, not airflow, fuel or the cabin heater.

• A: The cabin blower motor is electrically operated and independent of oil pickup restriction.
• B (correct): Correct: restricting the pump inlet may starve the oil circuit and compromise lubrication.
• C: Fuel metering does not depend on the pickup’s oil strainer function.
• D: An oil pickup cannot improve airflow through the radiator.

Answer: D

Correct answer: To allow oil flow when a filter path is excessively restrictive. A spring-loaded bypass valve opens when the pressure difference across the filter gets too high, as with a clogged element or thick cold oil at startup. Oil then flows around the media to the engine. The trade-off is deliberate: unfiltered oil is far less harmful than no oil at all. This is why skipping filter changes is risky; a clogged filter can leave the engine running on unfiltered oil without warning.

• A: Filter bypass action is not an octane-control process and has no link to the fuel system.
• B: Oil and coolant circuits should not be mixed by a filter bypass.
• C: Oil supply is most needed when an engine starts; a bypass valve is never meant to shut lubrication off.
• D (correct): Correct: bypassing a restricted filter can help maintain oil delivery while reducing filtration.

Answer: A

Correct answer: A full oil level does not rule out a real oil pressure problem. Oil level tells how much oil sits in the sump, while oil pressure tells how hard the pump is pushing oil through the passages. An engine can be full of oil and still have low pressure, so the warning must be treated as a serious signal and diagnosed.

• A (correct): Level and pressure measure different things; a worn pump or worn bearings can cause low pressure with a full sump.
• B: A full sump does not prove the pump is building pressure, so the warning cannot be dismissed.
• C: The level is at full, not over it, and overfilling would not be the usual cause of a pressure warning.
• D: The oil pressure light reports the lubrication circuit, not the coolant level.

Answer: C

Correct answer: 1.0 L. A shortfall is the gap between what should be there and what is there, so subtract the measured amount from the capacity:

Both readings were taken at the same specified condition, so the units match and no conversion is needed. Watch for answers that report the measured value itself or add the two numbers; the key words shortfall and difference both signal subtraction.

• A: 0.1 is ten times smaller than the given difference.
• B: 3.5 L is the measured amount rather than its shortfall.
• C (correct): Correct: 4.5 L minus 3.5 L equals 1.0 L under identical conditions.
• D: 8.0 is the sum of the quantities rather than their difference.

Answer: D

Correct answer: Allowing selected engine circulation before full radiator flow. When the engine is cold the thermostat stays closed, blocking flow to the radiator. If coolant could not move at all, hot spots could form near the cylinders and the thermostat would not sense the true temperature. A bypass passage lets the water pump circulate coolant through the block and head, warming the engine evenly, until the thermostat opens and sends flow to the radiator. It does not control fans, oil or speed.

• A: Fan-control logic differs by design; bypass coolant flow does not guarantee fan motion.
• B: Oil is not routed to intake air through a coolant bypass passage.
• C: Vehicle propulsion and throttle control are unrelated to coolant bypass passages.
• D (correct): Correct: an internal coolant bypass helps circulation during warm-up with limited radiator flow.

Answer: B

Correct answer: 3 kW. Energy is

60,000 J / 20 s = 3 kW.

• A: 0.6 kW is one fifth of the correct result because energy or time was mishandled.
• B (correct): Correct: energy is 3 × 4 × 5 = 60 kJ; 60,000 J / 20 s = 3 kW.
• C: 60 kW treats 60 kJ as if it were removed in one second.
• D: 12 kW incorrectly treats the total heat capacity as a rate.

Answer: A

Correct answer: Bearings can be damaged even while coolant temperature looks normal. Cooling and lubrication are separate systems with separate gauges. Coolant temperature can stay normal for a while because the cooling system is still working, yet without oil pressure the film between crankshaft journals and bearings disappears and metal begins to rub. Damage may happen before any rise in temperature shows. Assuming a normal temperature gauge means the engine is fine is the trap; each gauge reports only its own system.

• A (correct): Correct: lack of an oil film can destroy bearings independently of the coolant indication.
• B: The oil-pressure loss may have independent causes and does not prove radiator failure.
• C: Coolant quantity says nothing about oil pressure in the lubricating galleries, so it cannot prove the bearings are safe.
• D: A thermostat does not restore a failed oil pump or an oil-film supply loss.

Answer: C

Correct answer: 3,000 W. Power is energy transferred per unit of time, and 1 watt equals 1 joule per second. Convert kilojoules to joules first, 120 kJ = 120,000 J, then divide by 40 s to get 3,000 J/s. Forgetting the kilo conversion gives 3 W, and multiplying instead of dividing gives 4,800, so checking that the units come out as J/s is a quick way to catch either error.

• A: 30 is a hundredfold smaller than 3,000 W.
• B: 480 corresponds to multiplying or scaling the wrong quantities.
• C (correct): Correct: 120,000 J / 40 s gives 3,000 J/s, equal to 3,000 W.
• D: 300,000 overstates the power by a factor of 100.

Answer: B

Correct answer: 5°C. First find the total heat removed:

/s × 30 s = 180 kJ.

• A: This divides 180 kJ by 3.6 only and leaves out the 10 kg mass.
• B (correct): Q = 6 × 30 = 180 kJ, and ΔT = 180 ÷ (10 × 3.6) = 5°C.
• C: This divides 180 kJ by 10 only and leaves out the specific heat.
• D: This divides the 6 kW rate by 36 without first multiplying by the 30 s to get total heat.

Answer: A

Correct answer: A partly clogged radiator that cannot shed enough heat. Fine at idle but hot at highway speed or under heavy load means airflow is not the issue, since ram air already passes through the radiator. With coolant full and the fan working, a partly clogged radiator or weak pump flow that limits heat rejection is the best fit.

• A (correct): Overheating under high load at speed, with good fan operation and full coolant, points to limited heat-rejection capacity such as a restricted radiator.
• B: A stuck-open thermostat makes an engine run too cool, not overheat under load.
• C: The fan is confirmed working, and ram air covers airflow at highway speed, so a fan fault is unlikely.
• D: Oil level does not explain a rising coolant temperature that appears only under highway load.

Answer: A

Correct answer: 3°C. ΔT =

• A (correct): Correct: ΔT = Q/(mc) = 45/(5 × 3) = 3°C.
• B: A one-degree fall releases only 5 × 3 × 1 = 15 kJ in this model.
• C: A 45-degree drop would release 675 kJ, far above the stated amount.
• D: Nine degrees would correspond to 135 kJ, three times the required energy.

Answer: B

Correct answer: Both restrictions can reduce heat rejection even if oil pressure is normal. A radiator sheds heat only when coolant moves through it and air moves across its fins; cutting either flow reduces heat rejection and raises coolant temperature. Oil pressure, by contrast, depends on the oil pump, oil level and bearing clearances. The two systems share the engine but are monitored separately, so a good reading on one says nothing about the other. Treating one normal gauge as proof of overall health is a common error.

• A: Oil pressure says little about radiator heat transfer and does not guarantee coolant cooling.
• B (correct): Correct: separate airflow and coolant-flow restrictions can each impair cooling independently of oil-pressure reading.
• C: Thermostat operation normally controls coolant path rather than lubricating oil pump pressure.
• D: The oil filter has no direct radiator-airflow function in the conventional engine.

Answer: B

Correct answer: Oil pump. A circulation diagram is a closed loop, so the last item must connect back to the first. The pickup is the tube and screen that draws oil from the pan, and its only job is to feed the pump inlet. Once the pump is listed again, the cycle of pump, filter, bearings, sump and pickup is complete. Radiator fins and heater cores belong to the coolant circuit, which never shares oil passages.

• A: Radiator fins transfer coolant heat to air rather than receive oil from the sump pickup.
• B (correct): Correct: the pickup feeds the oil pump, completing the wet-sump lubrication circuit.
• C: Heater cores handle cabin heating through coolant, not the oil pickup path.
• D: Ignition sparks are unrelated to oil circulation paths.

Answer: C

Correct answer: 268°F. Each psi raises the boiling point by about 3°F, so 15 psi adds

The new boiling point is

• A: This subtracts the 45°F rise; pressure raises the boiling point, it does not lower it.
• B: This ignores the pressure, but a pressurized system boils at a higher temperature.
• C (correct): 15 psi × 3°F per psi = 45°F, and 223 + 45 = 268°F.
• D: This adds the 15 psi directly as degrees instead of multiplying by 3°F per psi.

Answer: A

Correct answer: A leaking heater core. Coolant can be lost without a puddle when it leaks internally. Normal exhaust and clean oil argue against a head gasket, while a damp floor, fogged glass, and a sweet smell inside the car point to coolant escaping from the heater core behind the dashboard.

• A (correct): A heater core leak sends coolant into the cabin, which explains the damp floor, fogging, and sweet smell without any outside drip.
• B: A head gasket leak usually shows white exhaust vapor or milky oil, and both are normal here.
• C: A stuck-closed thermostat causes overheating; it does not make coolant disappear into the cabin.
• D: A pump weep-hole leak drips or crusts at the front of the engine, not inside the cabin.

Answer: C

Correct answer: 432 kJ. Use

All three given values must appear in the product.

• A: This is only 9 × 3.2; the temperature change of 15°C was left out of the product.
• B: This multiplies mass by temperature change but drops the specific heat.
• C (correct): Multiplying mass, specific heat, and temperature change gives 9 × 3.2 × 15 = 432 kJ.
• D: This is ten times too large, a decimal slip when multiplying by 3.2.

Answer: C

Correct answer: Oil pickup screen. Sort by the fluid each part handles. The pickup screen handles oil on its way from the sump to the oil pump; the thermostat, heater core, and recovery tank all handle coolant.

• A: The thermostat controls how much coolant goes to the radiator, so it is a cooling part.
• B: The heater core carries hot engine coolant to warm the cabin, so it belongs to the cooling system.
• C (correct): The pickup screen sits in the sump and keeps large debris out of the oil pump, so it is part of the oil circuit.
• D: The coolant recovery tank holds expanding coolant, so it is a cooling-system part.

Answer: D

Correct answer: The A/C condenser sits in front of the radiator and needs airflow too. The A/C condenser is mounted in front of the radiator and must reject heat to passing air just as the radiator does. At low speed there is little ram air, so the fan is commanded on with the A/C to keep air flowing through both.

• A: The compressor is not the reason; the fan helps the condenser and radiator, which sit in the airflow at the front.
• B: The fan is also switched on by coolant temperature, so A/C is not its only trigger.
• C: A fan moves air; it does not relieve coolant pressure, which is the pressure cap's job.
• D (correct): The condenser sheds heat into the same air stream as the radiator, so the fan runs to keep air moving through both.

Answer: D

Correct answer: How the oil performs in cold-temperature viscosity tests. In a multi-grade label the number before the W (winter) rates how the oil flows in cold tests, and the number after the dash rates viscosity when hot. In 10W-40, the 10 is the cold rating and the 40 is the hot rating.

• A: The grade says nothing about change intervals; those come from the manufacturer's schedule.
• B: That is the number after the dash, the 40 in this label.
• C: W means winter here, not weight in pounds; the label is a viscosity rating.
• D (correct): The W stands for winter, and the number before it rates cold flow; a lower number flows better when cold.

Answer: A

Correct answer: Water jackets. Heat conducts through the cylinder wall into coolant flowing in passages called water jackets. The coolant then carries that heat to the radiator.

• A (correct): Water jackets are the cast passages where coolant picks up heat from the cylinder walls and head.
• B: Galleries are drilled passages that carry pressurized oil to the bearings, not coolant.
• C: Intake runners carry air into the cylinders; they are not coolant passages.
• D: Radiator tubes are in the radiator at the front of the car, not inside the block and head.

Answer: B

Correct answer: Air trapped in the cooling system after the refill. The symptoms began right after the coolant was replaced. Air trapped at high points such as the heater core and near the temperature sensor carries heat poorly, so the heater blows cold and the gauge reads erratically. The fix is to fill and bleed the system using the manufacturer's procedure.

• A: A stuck-open thermostat makes the gauge read steadily low; it does not cause bubbling or a jumping gauge right after a coolant change.
• B (correct): Air pockets near the heater core and sensor cause cold heat and odd gauge readings, and the timing right after a coolant service fits this.
• C: The oil pump is part of the lubrication system and has nothing to do with heater output or coolant bubbles.
• D: Oil viscosity does not affect cabin heat or the coolant temperature reading this way.

Answer: A

Correct answer: 2 kW. First find the heat:

Convert the time: 1.5 min × 60 = 90 s.

• A (correct): Q = 4.5 × 4.0 × 10 = 180 kJ, and 1.5 minutes is 90 s, so P = 180 ÷ 90 = 2 kJ/s = 2 kW.
• B: This divides 180 kJ by 1.5 without converting minutes to seconds.
• C: This is the total heat Q, not the rate; it was never divided by the time.
• D: This divides the time by the heat (90 ÷ 180), turning the formula upside down.

Answer: B

Correct answer: An oil pressure sensor, or sender. A pressure switch only changes state when pressure drops below a limit, which suits a warning light. A gauge that tracks pressure continuously needs a sensor (sender) whose output varies with pressure.

• A: A switch is only on or off at a set threshold, so it can light a warning lamp but cannot drive a smoothly moving gauge.
• B (correct): A sensor produces a signal that changes in proportion to pressure, which is what a moving gauge needle needs.
• C: Level and pressure are different measurements; a level sensor does not report how hard oil is being pushed.
• D: This sensor reports coolant temperature, not pressure in the lubrication circuit.

Answer: A

Correct answer: It would be cut in half. In

the rate is inversely proportional to thickness. Doubling d divides P by 2, so heat gets through the thicker wall half as fast.

• A (correct): Thickness d is in the denominator, so doubling it halves the rate.
• B: This treats thickness as if it were in the numerator; a thicker wall slows conduction.
• C: Only k, A, and ΔT were held constant; d changed, so the rate changes.
• D: That would need d squared in the formula; d appears only to the first power.

Answer: D

Correct answer: The engine may warm slowly and run too cool, while the real fault stays unfixed. Without a thermostat, coolant goes to the radiator even when the engine is cold, so it warms slowly, runs cool, gives weak cabin heat, and may lose fuel economy. Overheating is a symptom, so the real cause, such as a leak, weak pump, clogged radiator, or failed fan, still needs to be diagnosed.

• A: A thermostat does not create heat; it only opens and closes a path, so removing it cannot remove a heat source.
• B: If the real cause is a leak, weak pump, blocked radiator, or dead fan, that fault remains and overheating can return.
• C: Coolant flow and oil pressure are separate circuits; the thermostat has no effect on the oil pump.
• D (correct): With no thermostat the engine behaves like one with a stuck-open thermostat, and overheating is a symptom whose real cause has not been found.

Answer: D

Correct answer: Radiation. Radiation is heat carried by electromagnetic waves, mainly infrared, and it needs no contact or moving fluid. Very hot parts such as exhaust manifolds radiate strongly, which is why heat shields protect nearby wiring and fuel lines.

• A: Rising warm air does move some heat, but heat reaching your face sideways without moving air is mainly infrared radiation.
• B: Conduction needs direct contact or a material path, and you are not touching the manifold.
• C: Forced convection needs a pump or fan driving a fluid, and no air is blowing toward you.
• D (correct): Hot parts give off infrared waves that need no material in between, which is why heat shields are used near exhaust parts.

Answer: C

Correct answer: To hold oil in the filter after shutdown so pressure builds faster at startup. When the engine stops, oil could drain out of the filter back toward the sump. The anti-drainback valve keeps the filter full, so the pump does not have to refill it before pressure builds at the next start.

• A: That describes the bypass valve, a different feature that lets oil around a blocked element.
• B: Capping oil pressure is the job of the pressure relief valve in or near the pump.
• C (correct): Keeping the filter full means oil reaches the galleries sooner on the next start.
• D: Coolant is kept out by gaskets and walls, not by a filter valve.

Answer: B

Correct answer: It lowers the freezing point and raises the boiling point. Plain water freezes at 32°F, boils fairly easily, and lets metal rust. Adding glycol lowers the freezing point and raises the boiling point, and the inhibitors in the mix fight corrosion.

• A: Antifreeze is not added to thicken coolant; too much antifreeze actually reduces heat transfer.
• B (correct): Glycol widens the liquid range of the coolant, protecting against both freezing and boiling.
• C: Bearings are lubricated by engine oil; coolant never reaches them.
• D: Water is the better heat carrier; glycol is added for freeze and boil protection, not better heat transfer.

Answer: C

Correct answer: Into a cylinder through an internal leak, where it is burned. With no drips and no cabin signs, the coolant is leaving internally. Clean oil argues against a leak into the oil, while sweet white exhaust vapor shows coolant being burned in a cylinder. A cooling-system pressure test helps confirm where it escapes.

• A: A heater core leak would usually leave a damp carpet, fogged windows, or a sweet smell inside, none of which are present.
• B: A hose clamp leak would leave drips or crusty residue outside the engine, and none is found.
• C (correct): Sweet-smelling white exhaust vapor with no outside leak points to coolant entering a combustion chamber, such as through a head gasket.
• D: That would usually make the oil look milky, but the oil is clean.

Answer: B

Correct answer: 5 kg. Find the temperature change first:

• A: This is 252 ÷ 4.2; the temperature change was never used.
• B (correct): ΔT = 90 − 78 = 12°C, so m = 252 ÷ (4.2 × 12) = 252 ÷ 50.4 = 5 kg.
• C: This uses the final temperature of 90°C instead of the change of 12°C.
• D: This divides 4.2 × 12 by 252, which inverts the rearranged formula.

Answer: C

Correct answer: A pressurized film of oil that lifts and centers the shaft. Pressurized oil fed through the galleries forms a thin wedge-shaped film between the journal and the bearing shell. That film lifts and centers the shaft, so the parts do not touch while the engine runs. If oil supply fails, the film collapses and the bearings wear quickly.

• A: Crankshaft bearings are smooth replaceable shells, not ball bearings.
• B: Coolant never reaches the bearings; the cooling and oil circuits are kept separate.
• C (correct): This is hydrodynamic lubrication: the oil wedge carries the load so metal does not touch metal.
• D: The shaft must turn freely, so there is a small clearance that the oil film fills.

Answer: D

Correct answer: Recovery (overflow) tank. Coolant grows in volume as it heats. The cap releases the extra into the recovery tank, and when the engine cools, a vacuum valve in the cap pulls it back into the radiator so the system stays full.

• A: The heater core and its hoses pass coolant through to warm the cabin; they do not store expansion volume.
• B: The thermostat controls flow to the radiator by temperature; it does not hold extra coolant.
• C: The pump and its housing circulate coolant but have no space for expanded fluid.
• D (correct): The cap lets expanding coolant pass into this tank, and a vacuum valve draws it back as the system cools.

Answer: C

Correct answer: 0W-20, because the lower number before the W means better cold flow. Compare the numbers before the W, which rate cold-test behavior: 0 is lower than 10, so 0W-20 flows more easily when cold. The numbers after the dash, 20 and 30, describe hot viscosity, which matters later once the engine warms.

• A: Higher numbers mean thicker oil in the matching test, so 10W flows less easily when cold.
• B: The number before the W differs between the two, so their cold behavior differs.
• C (correct): The winter number rates cold-test behavior, and the lower 0W rating flows better at a cold start.
• D: The 30 rates viscosity when hot, not at a cold start, so it does not answer the cold-flow question.

Answer: B

Correct answer: A pressure relief valve stuck closed. A positive-displacement oil pump makes more pressure as oil gets thicker and rpm rises. The relief valve normally opens at a set limit to route the extra oil back. If it is stuck closed, pressure on a cold start can climb high enough to blow out a filter seal.

• A: A clogged pickup starves the pump, which lowers oil pressure rather than raising it.
• B (correct): If the relief valve cannot open, nothing limits pump pressure when cold, thick oil resists flow, so pressure can climb high enough to burst a filter seal.
• C: A relief valve stuck open dumps oil back to the inlet and causes low pressure, not high pressure.
• D: An open bypass lets oil skip the filter element, which eases flow; it does not raise pressure.

Answer: D

Correct answer: Engine oil. Pistons cannot touch coolant, so oil from the lubrication system is sprayed at their undersides to absorb heat. This shows that oil does some cooling, and that low oil pressure can let pistons run hotter than designed.

• A: Coolant stays in the water jackets and never reaches the pistons; the two fluids must not mix.
• B: Fuel is delivered by the injectors for combustion, not sprayed under pistons to cool them.
• C: Water is part of the coolant circuit only and is never sprayed inside the crankcase.
• D (correct): The jets are fed by the lubrication system, and the oil absorbs piston heat before draining to the sump.

Answer: A

Correct answer: A wax pellet that expands as it heats and pushes the valve open. A typical thermostat contains a wax pellet. When coolant reaches the rated temperature, often around 180 to 200°F, the wax expands and pushes the valve open so coolant can flow to the radiator.

• A (correct): The wax expands at the thermostat's rated temperature and moves the valve.
• B: The fan relay controls the fan, not a conventional thermostat valve.
• C: The cap's pressure affects boiling point; a typical thermostat responds to temperature, not cap pressure.
• D: Pump speed changes flow, but a typical thermostat opens because of temperature, not rpm.

Answer: A

Correct answer: Thinner oil causes less drag, which helps fuel economy. Oil reduces friction, but moving and shearing oil itself takes energy, and thicker oil causes more drag. Specifying a thinner grade, when the engine is designed for it, cuts that drag and improves fuel economy.

• A (correct): Pumping and shearing thicker oil costs more energy, so a thinner specified grade reduces those losses.
• B: All oil wears out its additives and collects contaminants, so it still needs changes on schedule.
• C: Every pressure-fed engine still needs an oil pump to make the flow.
• D: Oil grade has no effect on coolant boiling point; the pressure cap and glycol do that.

Answer: D

Correct answer: Fuel diluting the engine oil. Fuel dilution happens when unburned fuel reaches the oil, often from many short trips, rich running, or a leaking injector. The oil smells of gasoline and becomes thinner, so changes on the severe-service schedule and occasional longer drives help.

• A: Coolant contamination usually makes oil look milky, not smell of gasoline.
• B: That raises oil pressure; it does not add a gasoline smell to the oil.
• C: The problem described is oil that has become thinner, not thicker.
• D (correct): Short trips that never fully warm the engine let fuel collect in the oil, thinning it and giving a gasoline smell.

Answer: C

Correct answer: Air forced through the grille by the car's motion cools the radiator. At highway speed the car's own motion pushes air through the grille and radiator. This ram air usually removes plenty of heat, so the fan barely runs; the fan is needed mostly at idle and in slow traffic.

• A: A closed thermostat would cause overheating, not normal temperature.
• B: The engine still makes a great deal of heat on the highway; it just has enough airflow to shed it.
• C (correct): This ram air moves plenty of air through the radiator fins, so the fan is rarely needed.
• D: Engine oil coolers handle only oil heat and are not on every engine; the radiator still does the main job.

Answer: A

Correct answer: A softened lower hose collapsing under pump suction. The lower hose carries coolant from the radiator to the pump inlet, where there is suction. A hose that has turned soft can collapse as pump speed rises, cutting coolant flow under high load. Replacing the hose restores flow.

• A (correct): The lower hose feeds the pump inlet; a weak hose can be sucked flat at high rpm and choke coolant flow just when the most heat must be removed.
• B: A stuck-open thermostat makes the engine run cool, not overheat at speed, and it would not flatten a hose.
• C: The fan is confirmed working, and a fan fault shows up mostly at idle, not at highway speed where ram air takes over.
• D: The oil pump is in the lubrication circuit and cannot flatten a radiator hose or limit coolant flow.

Answer: B

Correct answer: Follow the manufacturer's schedule, using the severe-service interval for towing or short trips. Maintenance details such as oil grade and change interval depend on the specific engine. The manufacturer's schedule is the guide, and driving that counts as severe service, like towing or frequent short trips, usually calls for more frequent changes.

• A: Oil grade, capacity, and intervals vary from engine to engine, so one rule does not fit all.
• B (correct): The owner's manual is the authority, and severe service such as towing or many short trips often calls for shorter intervals.
• C: Color is a poor guide; additives wear out and contaminants build up even when oil still looks fine.
• D: A full level does not mean the additives are still working or that the oil is clean.

Answer: B

Correct answer: It sends extra engine heat into the cabin through the heater core. The heater core is a small radiator fed by engine coolant. With heat on full and the blower on high, it sheds some extra engine heat into the cabin. It is only a temporary measure; the driver should still pull over safely as soon as possible.

• A: The heater core carries coolant, not oil; the oil circuit is separate.
• B (correct): Hot coolant flows through the heater core, and the blower moves heat from it into the cabin, acting like a small second radiator.
• C: The heater controls do not operate the thermostat, which responds to coolant temperature.
• D: The cap's rating is fixed by its spring; heater settings cannot change it.