Five free practice questions on lubrication and cooling systems: content area D of the ASE A1 Engine Repair test, 8 of its 45 scored questions (17.8%). They are in the ASE format: four options, one best answer. Answer each one before opening the explanation. No account, no email.
01The questions
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Some engines use a variable-displacement oil pump that the PCM commands to a lower output at light load once the engine is warm. What is the main reason for this?
- To keep the oil filter bypass valve from opening
- To reduce the engine power used to drive the pump
- To send more oil to the cam phasers at light load
- To let the oil warm up faster after a cold start
Show the answer
B. Correct. A fixed pump moves more oil than the engine needs at light load and dumps the excess over its relief valve, wasting engine power. Lowering displacement when demand is low cuts that drag and improves fuel economy; the PCM raises output again for high load, high rpm or oil-actuated systems that need it.
Why not the others
A. The filter bypass valve opens on a high pressure difference across the filter, mostly with cold oil or a clogged element. Pump displacement is reduced at light warm load to save the power used to drive the pump.
C. Lower displacement sends less oil, not more, to every circuit, including the cam phasers. The PCM raises pump output when the phasers or other oil-actuated systems need pressure and lowers it at light load to save power.
D. The stem places the lower output after the engine is warm, so warm-up is not the purpose. Reducing displacement at light load saves the power the pump would otherwise waste.
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A mechanical gauge on an engine with a chain-driven oil pump reads 0 psi at every engine speed. Any of these could be the cause EXCEPT:
- a broken chain between the crankshaft and the pump.
- an oil level that has dropped below the pickup.
- a pickup screen completely sealed off by sludge.
- a pressure relief valve stuck closed.
Show the answer
D. Correct. A relief valve stuck closed cannot release excess oil, so it raises pressure at higher rpm instead of eliminating it. A reading of 0 psi points to a pump that is not turning or not receiving oil.
Why not the others
A. If the pump drive chain breaks, the pump stops turning and no oil is pumped, so the gauge reads 0 psi at every speed. This is a genuine cause, checked by confirming the pump turns with the engine.
B. With the oil below the pickup, the pump draws only air and cannot build pressure, so 0 psi is possible. Checking the level is the first step before any teardown.
C. A screen sealed off by sludge starves the pump of oil, so it can build little or no pressure. This could produce a 0 psi reading, so it is a genuine cause.
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A vehicle's oil-life monitor calculates remaining oil life from engine revolutions, operating temperature and trip patterns; it has no sensor in the oil. After an oil and filter change, what must be done for it to show the new oil's life?
- Clear all stored DTCs with a scan tool
- Cycle the ignition so it restarts its count
- Reset the monitor by its own procedure
- Run the crankshaft position variation relearn
Show the answer
C. Correct. A calculated monitor has no way to know the oil was changed, so it keeps counting down from the old value until it is reset by the procedure the manufacturer gives (instrument panel buttons, a menu or a scan tool). Resetting it is part of the oil service.
Why not the others
A. Clearing DTCs erases fault codes and freeze-frame data; it is a different function from the oil-life reset. The monitor is reset by its own procedure.
B. A calculated monitor cannot tell that the oil was changed, so switching the ignition off and on only resumes the count from the old value. With no sensor in the oil, it shows the new oil's life only after it is reset.
D. The crankshaft position variation relearn teaches the PCM the tone wheel's tolerances for misfire detection after a sensor, crankshaft or PCM is replaced. It has nothing to do with oil life, which is reset by its own procedure.
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The heater blows only lukewarm air with the engine at normal temperature and the coolant full. With the controls at full heat, an infrared thermometer reads 195°F at the heater inlet hose and 110°F at the outlet hose, both near the firewall. Which of these could be the cause?
- A clogged cabin air filter
- A blend door stuck at full cold
- A thermostat stuck open
- A restricted heater core
Show the answer
D. Correct. Hot coolant reaches the core but little flows through it, so what does pass gives up its heat and leaves far cooler, an 85°F drop. A restricted core is back-flushed if the manufacturer allows, or replaced, and the system is checked for the scale or sludge that plugged it.
Why not the others
A. A clogged cabin filter cuts airflow, and with less air crossing the core less heat is removed, so the outlet hose would stay closer to inlet temperature. The large hose-to-hose drop points to too little coolant flow through the core.
B. With the blend door stuck cold, air bypasses the core, so the core gives up little heat and the outlet hose would be almost as hot as the inlet. A large drop across the core shows low flow through it.
C. A stuck-open thermostat makes the whole engine run cool, so the inlet hose would not read 195°F with the engine at normal temperature. The problem is in the flow through the core, not the engine's temperature.
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On an engine with an electrically heated thermostat, why does the PCM energize the heater in the thermostat under high load?
- To speed warm-up after a cold start
- To hold it shut until the engine warms up
- To open it at a lower coolant temperature
- To run the coolant hotter for fuel economy
Show the answer
C. Correct. The heater warms the wax pellet directly, so the thermostat opens before the coolant itself reaches the valve's normal opening point, lowering engine temperature for heavy load before it can climb. Unpowered at light load, the thermostat works on its higher built-in opening point and the engine runs warmer for efficiency.
Why not the others
A. Heating the pellet opens the thermostat, which sends coolant to the radiator and would slow warm-up. The heater is used to lower coolant temperature under high load.
B. A wax thermostat stays closed on its own when cold; the heater can only make it open sooner. The PCM energizes it to open the thermostat at a lower coolant temperature.
D. Running hotter for economy happens at light load with the heater off, using the thermostat's higher built-in opening point. Energizing the heater does the opposite and lowers coolant temperature.
02Answer key
| Question | Answer |
|---|---|
| Q1 | B |
| Q2 | D |
| Q3 | C |
| Q4 | D |
| Q5 | C |
03What area D covers
This content area covers the systems that keep oil moving and engine heat under control. Questions deal with oil pressure tests, oil leaks, oil pumps, oil coolers and oil changes, then cooling system pressure tests, radiators, caps, hoses, thermostats, water pumps, coolant testing and bleeding, cooling fans and fan clutches, and the drive belts and tensioners that turn the pumps.
The ASE test specification calls this content area “Lubrication and Cooling Systems Diagnosis and Repair”. It carries 8 of the 45 scored questions, 17.8% of the test.
- Test oil pressure and find oil leaks
- Inspect oil pumps, relief valves and oil coolers
- Change oil and filter to the maker's specification
- Pressure test the cooling system and cap
- Check radiators, heater cores, hoses and thermostats
- Replace water pumps; test, fill and bleed coolant
- Diagnose cooling fans, fan clutches and shrouds
- Inspect drive belts, pulleys and tensioners
04What the questions turn on
Confirm with a mechanical gauge
A mechanical gauge at the sender port shows whether the engine or the warning circuit is at fault. Pressure above the minimum puts the fault in the switch or circuit; 0 psi at every speed means the pump is not turning or not getting oil.
Temperatures show where flow stops
An infrared thermometer finds the restriction. A heater core with a hot inlet hose and a far cooler outlet hose has little coolant flowing through it, and a band of radiator tubes much colder than their neighbors is plugged.
Thermostat opening and lift
A thermostat is judged on both its opening temperature and how far it has opened at the specified higher temperature. One that starts to open on time but lifts too little still restricts flow under heavy load, and it is replaced, not adjusted.
What the cap's two valves do
Pressure on the coolant raises its boiling point. When the cap's vacuum valve sticks closed, coolant pushed into the reservoir when hot is not drawn back as the engine cools, so the radiator reads low while the reservoir sits at or above its mark.
05The other content areas
The A1 test has five content areas. Each has its own page of free questions:
The ASE A1 Engine Repair practice test page describes the full question bank. How these questions are written and checked: how our questions are made. Found a mistake? Tell us and we will fix it.
ToolboxPrep is an independent study site. It is not affiliated with or endorsed by ASE (the National Institute for Automotive Service Excellence). Our questions are original practice questions written to the published ASE test specifications; they are not actual test questions.