Area D has 8 of the 45 scored questions, the only A1 area whose count did not change from 2025 to 2026. Typical questions start from a gauge or a temperature: oil pressure that sags when the engine is hot, an engine that overheats only at idle, a filter gasket that blows out.
8scored questions on the test
18%of the scored questions
13tasks in the area
14questions on this page
What area D asks
From the 2026 task list, in our words:
Oil pressure: diagnose lubrication problems and run an oil pressure test; find oil leaks.
Oil pump: gears or rotors, housing and pickup; relief valve, pressure controls and the pump drive.
Oil coolers, inside and outside the engine; oil type, viscosity and rating to the manufacturer's spec.
Cooling system tests: pressure and leak tests; radiator, heater core, pressure cap and recovery tank.
Thermostats, including electronically controlled ones, and the coolant bypass.
Water pumps, including electric pumps; hoses, pipes and valves.
Coolant: test it, drain, flush and refill with the recommended type, and bleed the air out.
Airflow and drive: electric and mechanical fans, fan clutch, shroud, air dams and shutters; belts, tensioners and pulleys.
overheats at idle, fine at road speed: too little airflow, so check the fan, the fan clutch and the shroud;
overheats at higher rpm, normal at low rpm: in ASE's 2026 sample questions the answer is a worn water pump belt tensioner, a belt that slips as speed rises;
climbs fast with a cool upper hose: a thermostat stuck closed; slow warm-up and weak heat: stuck open;
overheating and no heat after a coolant job: air left in the system;
coolant in the oil: a head gasket, a crack, or a failed oil cooler.
14 lubrication and cooling questions
0 of 14 answered · 0 correct
Question 1 of 14 · Lubrication and Cooling Systems Diagnosis and Repair · 18%Not answered
A rebuilt engine exhibits low oil pressure at hot idle, but pressure is normal when cold. During teardown, the technician measures the oil pump rotor-to-housing clearance and finds it exceeds the manufacturer's maximum specification. What is the required repair?
Explanation
Incorrect: The pump's internal clearance is the problem, and machining the block will not tighten it.
Incorrect: Heavier oil only masks the worn pump.
Correct: Rotor-to-housing clearance beyond the maximum means the pump is worn, so it has to be replaced.
Incorrect: A higher relief valve setting hides a worn pump and does nothing for its internal leakage.
Incorrect: Shimming the relief spring changes the pressure cap, not the leakage inside a worn pump.
Question 2 of 14 · Lubrication and Cooling Systems Diagnosis and Repair · 18%Not answered
A technician replaces a failed engine oil pump. Within two days of normal driving, the replacement pump fails catastrophically, and the engine loses all oil pressure again. Which of the following procedural omissions during the initial repair is the most likely cause of this rapid secondary failure?
Explanation
Incorrect: The sending unit only reports pressure; it cannot cause the pump to fail.
Incorrect: Oil viscosity does not destroy a new pump in two days.
Correct: The debris that killed the first pump is still in the pickup screen and galleries, and the new pump ingests it.
Incorrect: Overtightened pan bolts cause leaks, not a destroyed pump.
Incorrect: Most oil pumps are not belt-driven; a reused accessory belt has nothing to do with the oil pump.
Question 3 of 14 · Lubrication and Cooling Systems Diagnosis and Repair · 18%Not answered
A customer reports an intermittent oil pressure warning and lifter ticking during hard cornering. The engine oil level is correct and the oil pressure gauge fluctuates while cornering. Which of the following is the most likely cause?
Explanation
Incorrect: A faulty sender cannot make the lifters tick.
Incorrect: A worn relief valve would cause pressure trouble in a straight line too, not just in corners.
Incorrect: A restricted filter gives steady low pressure regardless of cornering.
Incorrect: Worn cam bearings lower pressure all the time, not only when cornering.
Correct: When oil sloshes away from the pickup in a turn, a crack above the oil line lets the pump suck air, so pressure flickers and the lifters tick.
Question 4 of 14 · Lubrication and Cooling Systems Diagnosis and Repair · 18%Not answered
An engine has normal oil pressure when cold (45 psi at idle) but drops to 10 psi at idle when fully warmed. An oil analysis shows elevated copper and lead particles. Which of the following is the most likely cause?
Explanation
Incorrect: A bad sender misreports pressure but cannot put bearing metal into the oil.
Incorrect: Oil that is too thin would lower hot pressure, but it does not put copper and lead into the oil.
Incorrect: A restricted filter does not add copper and lead to the oil.
Correct: Copper and lead come from bearing linings, and worn bearings bleed off hot, thin oil, so pressure collapses when warm.
Incorrect: A relief valve stuck open would also give low cold pressure, and cold pressure is normal here.
Question 5 of 14 · Lubrication and Cooling Systems Diagnosis and Repair · 18%Not answered
After an engine rebuild, the oil pressure gauge reads 100 psi at idle. The oil pressure relief valve was replaced and its spring was shimmed during assembly. Which of the following is the MOST likely cause of the high oil pressure?
Explanation
Correct: Shimming the relief spring raises the pressure at which it opens, so after the rebuild it holds oil pressure far above normal.
Incorrect: A filter bypass valve does not regulate gallery pressure.
Incorrect: Worn pump gears leak internally and lower output, so they cannot cause 100 psi at idle.
Incorrect: Thin oil lowers pressure.
Incorrect: Extra bearing clearance lowers pressure, not raises it.
Question 6 of 14 · Lubrication and Cooling Systems Diagnosis and Repair · 18%Not answered
What indicates a stuck-closed thermostat?
Explanation
Incorrect: An overheating engine still sends hot coolant through the heater core, so the heater does not blow cold.
Incorrect: A radiator leak is a separate fault, not a sign of the thermostat.
Incorrect: Never warming up is the symptom of a thermostat stuck open.
Correct: A closed thermostat blocks flow to the radiator, so the engine overheats while the lower hose stays cool.
Question 7 of 14 · Lubrication and Cooling Systems Diagnosis and Repair · 18%Not answered
What is the first step when diagnosing an engine with sudden loss of oil pressure?
Explanation
Incorrect: Replacing the pump before checking the level skips the most likely cause.
Incorrect: Pulling the pan is a teardown step for after the simple checks.
Correct: Low oil is the most common and cheapest cause of a sudden pressure loss, so the dipstick is checked before anything else.
Incorrect: A filter change does not address a sudden pressure loss and skips the level check.
Question 8 of 14 · Lubrication and Cooling Systems Diagnosis and Repair · 18%Not answered
What does a chirping noise that changes with engine RPM typically indicate?
Explanation
Incorrect: A failing water pump bearing grinds or squeals constantly instead of chirping with belt slip.
Correct: A glazed or worn belt slips briefly on its pulleys and chirps in step with engine speed.
Incorrect: Low oil pressure causes lifter tick or a warning light, not a chirp at the front of the engine.
Incorrect: A failing alternator shows up as charging problems or a bearing whine, not a belt chirp.
Question 9 of 14 · Lubrication and Cooling Systems Diagnosis and Repair · 18%Not answered
What can cause engine overheating at idle but normal temperature at speed?
Explanation
Incorrect: A bad thermostat overheats the engine at any speed, not only at idle.
Correct: At speed, ram air cools the radiator, so overheating only at idle means the electric fan is not pulling air through.
Incorrect: Low coolant makes the engine run hot under all conditions, especially under load.
Incorrect: A head gasket leak tends to overheat the engine under load, not only at idle.
Question 10 of 14 · Lubrication and Cooling Systems Diagnosis and Repair · 18%Not answered
An engine has low oil pressure at the gauge sending unit, but a mechanical gauge installed at the oil pump outlet shows normal pressure. The oil level is correct. Which of the following is the most likely cause?
Explanation
Incorrect: A relief valve stuck open dumps oil at the pump and lowers outlet pressure.
Incorrect: A clogged pickup screen starves the pump inlet, so the outlet pressure would be low too.
Incorrect: Excessive bearing clearance lowers pressure everywhere, including at the pump outlet.
Incorrect: Worn pump gears would lower pressure right at the pump outlet, which reads normal.
Correct: Normal pressure at the pump outlet but low pressure further down the line means something between them, the filter, is choking flow.
Question 11 of 14 · Lubrication and Cooling Systems Diagnosis and Repair · 18%Not answered
What causes oil aeration?
Explanation
Correct: When the level is too high, the spinning crankshaft dips into the oil and whips it into foam.
Incorrect: A dirty filter restricts flow but does not churn air into the oil.
Incorrect: Coolant level has nothing to do with air getting into the engine oil.
Incorrect: The wrong viscosity changes pressure and flow, not the amount of air beaten into the oil.
Question 12 of 14 · Lubrication and Cooling Systems Diagnosis and Repair · 18%Not answered
When testing a radiator cap with a pressure tester, which of the following results indicates the cap needs replacement?
Explanation
Incorrect: Holding exactly its rated pressure is what a good cap does.
Incorrect: Normal compression marks on the gasket are expected and do not mean the cap has failed.
Incorrect: A clean, flexible seal is a sign of a healthy cap.
Correct: A cap that vents before reaching its rated pressure lowers the boiling point of the system and has to be replaced.
Question 13 of 14 · Lubrication and Cooling Systems Diagnosis and Repair · 18%Not answered
During a comprehensive evaluation of a high-performance engine, the technician observes that engine oil temperature rises abnormally under heavy load conditions, even though the oil pressure remains within normal limits. Inspection of the traditional cooling components, including the radiator, water pump, and thermostat, reveals no faults. Which of the following components should be checked next to diagnose the source of the high oil temperatures?
Explanation
Incorrect: A faulty sensor would misread coolant temperature; the high oil temperature here is real.
Incorrect: Restricted coolant passages would show up as cooling-system overheating, which was ruled out.
Correct: When the radiator, pump and thermostat all check out, the auxiliary oil cooler is what sheds oil heat under heavy load.
Incorrect: A blocked filter shows up as pressure trouble or bypassing, not high oil temperature with normal pressure.
Question 14 of 14 · Lubrication and Cooling Systems Diagnosis and Repair · 18%Not answered
After refilling a cooling system that has a bleeder screw on the thermostat housing, what is the proper way to remove the trapped air?
Explanation
Correct: With the bleeder open, air at the high point escapes as the coolant rises, and closing it once steady coolant comes out leaves no air pocket.
Incorrect: Filling only the overflow tank leaves the air pocket in the engine untouched.
Incorrect: Pressurizing past the cap rating stresses the hoses and radiator and does not vent the trapped air.
Incorrect: Revving with the system closed traps the air and can overheat the engine before the pocket moves.
Answer every question to see your score
Trust a mechanical gauge first
Several questions hinge on the difference between the dash reading and the engine's real oil pressure. Before you condemn a pump or the bearings, put a mechanical gauge on the sender port. A sender that reads low on an engine with good pressure is a five-minute fix, and the wrong answer is an engine teardown.
Fast overheating, often with the upper radiator hose staying cool because coolant isn't reaching the radiator. A thermostat stuck open does the opposite: slow warm-up, a low gauge reading and weak heater output.
Why does an engine overheat at idle but not on the highway?
At road speed, ram air cools the radiator; at idle the fan does all the work. Check the electric fan and its circuit, the fan clutch on a belt-driven fan, and a missing or damaged shroud.
What causes low oil pressure when the engine is hot?
Warm oil is thinner and leaks through clearances faster, so worn main or rod bearings show up hot first. Oil of the wrong viscosity and fuel-diluted oil do the same. Confirm with a mechanical gauge before you blame the engine.