22 A1 — Engine Repair Practice Questions & Answers

1. 1. During a cranking compression test one cylinder reads far below the others. A small amount of engine oil is squirted into that cylinder and the test is repeated; the reading rises sharply. What does this result indicate?

   • A.Worn rings or a scored cylinder wall, since oil seals the ring gap briefly✓ Answer
   • B.A burnt exhaust valve, because a seat that does not seal is unaffected by oil
   • C.A worn camshaft lobe that has reduced valve lift on that one cylinder
   • D.A head gasket leak into the cooling jacket above that cylinder's chamber

   Oil poured into the bore momentarily seals the gap between the rings and the cylinder wall, so a reading that jumps on the wet test places the leak at the rings or the bore. Oil cannot seal a leaking valve or a breached head gasket, so those faults produce little or no change on the wet test.

   Source: ASE A1 Engine Repair Task List, General Engine Diagnosis — cranking, running, and wet compression testingReport a problem with this question

2. 2. A cranking compression test shows all cylinders low but within a few points of each other. The engine starts and idles but has almost no power. Which cause best fits this pattern?

   • A.A plugged catalytic converter restricting flow out of the cylinders
   • B.A head gasket leaking between two adjacent cylinders at mid-block
   • C.A single burnt exhaust valve leaking on every compression stroke
   • D.A timing chain or belt that has jumped, retarding valve timing✓ Answer

   A loss that is spread evenly over every cylinder must come from something all the cylinders share, and valve timing is that shared item: a jumped chain or belt shifts every valve event equally, so each cylinder loses the same amount. A burnt valve or a head gasket leak affects only the cylinders it touches and would show up as one or two low readings against normal ones.

   Source: ASE A1 Engine Repair Task List, Cylinder Head and Valve Train — verify valve timing; General Engine Diagnosis — compression testingReport a problem with this question

3. 3. Two cylinders next to each other read equally low on a cranking compression test. The engine loses coolant with no external leak and puffs white smoke at start-up. What is the most likely cause?

   • A.A leaking radiator core that lets coolant escape only when hot
   • B.A cracked exhaust manifold drawing outside air into those two ports
   • C.Two intake valves with excessive stem-to-guide clearance and worn seals
   • D.A head gasket failure between those two cylinders and into a coolant passage✓ Answer

   Equal low compression on two cylinders that sit side by side points to the sealing surface they share, which is the head gasket land between them. When that same failure also opens into a water jacket, coolant is consumed internally and burned, which is what produces the white exhaust smoke with no puddle under the vehicle.

   Source: ASE A1 Engine Repair Task List, General Engine Diagnosis — diagnose coolant consumption and abnormal exhaust colorReport a problem with this question

4. 4. A cylinder leakage test is performed with the piston at TDC on the compression stroke. Air is heard escaping from the tailpipe. Which condition does this indicate?

   • A.Worn rings letting air pass down into the crankcase
   • B.An exhaust valve that is not seating in that cylinder✓ Answer
   • C.An intake valve that is not seating in that cylinder
   • D.A head gasket leaking into the coolant passage nearby

   In a leakage test the escape point identifies the leak path, and the only route from the combustion chamber to the tailpipe is past the exhaust valve. Air at the throttle body would mean the intake valve, air at the oil fill would mean the rings, and bubbles in the coolant would mean the head gasket or a crack.

   Source: ASE A1 Engine Repair Task List, General Engine Diagnosis — perform cylinder leakage tests and determine needed actionReport a problem with this question

5. 5. During a cylinder leakage test, bubbles appear in the coolant at the radiator filler neck while the cylinder is held pressurized. What should the technician conclude?

   • A.Air is passing the exhaust valve and out through the tailpipe
   • B.Air is entering the cooling system past the head gasket or a crack✓ Answer
   • C.Air is leaking past the intake valve into the induction system
   • D.Air is passing the rings and pressurizing the engine crankcase

   Cylinder pressure can only reach the coolant if the barrier between the combustion chamber and a water jacket has been breached, which means a failed head gasket or a cracked head or block. That is also why the same engine will typically push coolant out of the recovery tank and fail to hold cooling-system pressure.

   Source: ASE A1 Engine Repair Task List, General Engine Diagnosis — cylinder leakage testing; Lubrication and Cooling — cooling system pressure testingReport a problem with this question

6. 6. A cylinder leakage test is being discussed. Technician A says air heard at the throttle body means the intake valve is not sealing. Technician B says air heard at the oil fill opening means the rings or cylinder wall are worn. Who is correct?

   • A.Technician A only
   • B.Technician B only
   • C.Both Technician A and Technician B✓ Answer
   • D.Neither Technician A nor Technician B

   Both statements match the standard escape-point map used to read a leakage test: the intake tract connects to the chamber only through the intake valve, and the crankcase connects only past the piston rings. Because each escape point has one unique path back to the combustion chamber, the location of the hiss identifies the failed part without further disassembly.

   Source: ASE A1 Engine Repair Task List, General Engine Diagnosis — perform cylinder leakage testsReport a problem with this question

7. 7. An engine has a heavy knock that is present only with the transmission in DRIVE and the brakes applied. At the same rpm in PARK and NEUTRAL the noise is gone. What is the most likely cause?

   • A.A vibration damper with a loose hub and a separated elastomer ring
   • B.A worn connecting rod bearing that knocks whenever the engine is loaded
   • C.Piston-to-wall clearance that produces slap once the engine is loaded
   • D.A cracked flexplate or a torque converter that is failing under load✓ Answer

   A noise that appears only when the converter is coupled to a driving gear is being produced by a part that is loaded only in gear, and the flexplate and torque converter are the components that fit that description. An internal bearing knock is driven by combustion load and would still be audible when the engine is loaded in NEUTRAL or when rpm is raised in PARK.

   Source: ASE A1 Engine Repair Task List, General Engine Diagnosis — locate and identify engine noises and vibrationsReport a problem with this question

8. 8. On the first start of the day an engine makes a light rapping from the top of the engine that fades after a few seconds and does not return until the next morning. What is the most likely cause?

   • A.A worn camshaft lobe that becomes quieter as the oil film thickens
   • B.Excess piston clearance that quiets down as the pistons expand
   • C.Oil draining from the lifters overnight past a failed anti-drainback valve✓ Answer
   • D.A valve set with too little lash that closes up as the head warms

   A tap that appears only on the first start and stops within seconds is the sound of hydraulic lifters running dry until oil pressure refills them, which happens when oil drains back out of the galleries overnight. The anti-drainback valve in the filter, or a lifter that bleeds down, is what allows that drain-back, so the noise tracks how long the vehicle has been sitting rather than engine temperature.

   Source: ASE A1 Engine Repair Task List, General Engine Diagnosis — locate and identify engine noises; Lubrication — oil filter and lubrication system serviceReport a problem with this question

9. 9. An engine has a heavy knock that is loudest under acceleration. When the ignition to number four cylinder is disabled, the knock becomes noticeably quieter. Which component is the most likely source?

   • A.The number four connecting rod bearing✓ Answer
   • B.The crankshaft thrust bearing surface
   • C.The vibration damper on the crank snout
   • D.A collapsed hydraulic lifter on number four

   A rod bearing knock is created by combustion pressure driving a loose rod against its journal, so removing the firing event on that cylinder removes most of the load and the noise drops. A lifter or damper noise is not produced by cylinder pressure and would not change when that one cylinder is shorted out.

   Source: ASE A1 Engine Repair Task List, General Engine Diagnosis — cylinder power balance testing and engine noise diagnosisReport a problem with this question

10. 10. A cooling system is pressurized with a hand pump and the pressure bleeds down steadily, yet no coolant can be found anywhere outside the engine. Which action best identifies where the coolant is going?

    • A.Top off the system and tell the customer to watch the level
    • B.Test the coolant for combustion gases with a block-check tester✓ Answer
    • C.Replace the radiator cap and refill the system with fresh coolant
    • D.Add a stop-leak product and recheck the pressure after a road test

    A system that will not hold pressure with no visible external leak means the coolant is leaving internally, into a cylinder, into the oil, or into the transmission cooler, and the combustion-gas test is the check that confirms a combustion-to-coolant breach. Sealer or a new cap replaces parts before the leak path has been identified, which reverses the correct verify-test-then-repair order.

    Source: ASE A1 Engine Repair Task List, Lubrication and Cooling Systems — perform cooling system pressure and leak testsReport a problem with this question

11. 11. An engine stays at normal temperature in stop-and-go traffic but overheats after twenty minutes at highway speed. Technician A says a failed electric cooling fan explains it. Technician B says a thermostat stuck open explains it. Who is correct?

    • A.Technician A only
    • B.Both Technician A and Technician B
    • C.Technician B only
    • D.Neither Technician A nor Technician B✓ Answer

    At highway speed ram air through the grille does the cooling, so the fan is not needed and a dead fan shows up as overheating at idle or in traffic instead. A thermostat stuck open causes slow warm-up and cool heater output rather than overheating, so this pattern points to a restricted radiator core, a slipping belt or failed tensioner, or a water pump whose impeller cannot keep up at high output.

    Source: ASE A1 Engine Repair Task List, Lubrication and Cooling Systems — diagnose cooling system problems; inspect and test radiator, fans, belts and tensionersReport a problem with this question

12. 12. A vehicle takes an unusually long time to warm up, heater output is barely warm at highway speed, and a code for coolant temperature below the thermostat regulating temperature is stored. What is the most likely cause?

    • A.An air pocket trapped in the system after a recent coolant refill
    • B.A thermostat that is stuck open so the coolant is never regulated properly✓ Answer
    • C.A heater core that is plugged and restricting flow through the box
    • D.A thermostat stuck closed that keeps coolant out of the radiator

    The thermostat exists to restrict flow to the radiator until the engine reaches operating temperature, so one held open lets coolant circulate through the radiator continuously and the engine never gets hot enough, which is exactly what the below-regulating-temperature code reports. A plugged heater core or an air pocket gives poor heat with normal engine temperature, and a thermostat stuck closed causes rapid overheating instead.

    Source: ASE A1 Engine Repair Task List, Lubrication and Cooling Systems — inspect and test thermostat, bypass, and housingReport a problem with this question

13. 13. A cooling system uses a cap rated at 15 psi. The cap no longer holds its rated pressure, and the engine boils over on a long climb even though coolant level and fan operation check out. Which explanation is correct?

    • A.Coolant boils sooner because a cap holding less pressure raises the boiling point less✓ Answer
    • B.Coolant expands more than normal because the cap seals the recovery hose
    • C.Coolant absorbs less heat because the pump cavitates at low system pressure
    • D.Coolant flows too fast through the radiator and cannot give up its heat

    A pressure cap raises the boiling point of the coolant by roughly 3 degrees F for each psi it holds, so a cap that cannot reach its rating leaves the coolant boiling at a much lower temperature and the system erupts on a hard pull. The cap also has to seal so coolant can be drawn back from the recovery tank as the engine cools, which is why a weak cap shows up as both boil-over and a chronically low level.

    Source: ASE A1 Engine Repair Task List, Lubrication and Cooling Systems — inspect and test pressure cap and coolant recovery systemReport a problem with this question

14. 14. This question contains the word EXCEPT. Read the question carefully before choosing your answer. An engine shows low oil pressure at hot idle, confirmed with a mechanical gauge at the sending unit port. Each of the following could cause this reading EXCEPT:

    • A.A pressure relief valve stuck closed in its bore by varnish✓ Answer
    • B.Main and rod bearing clearances that have opened up with wear
    • C.A pickup screen partly blocked by sludge in the oil pan
    • D.A pressure relief valve held open by debris caught in its bore

    A relief valve that cannot open keeps oil from being dumped back to the pan, so it raises system pressure rather than lowering it, and it is often found when pressure is high and a filter or cooler is damaged. Low pressure at hot idle comes from too much leakage or too little supply: enlarged bearing clearances, a relief valve held open, a restricted pickup, or oil that is thinned by heat or fuel dilution.

    Source: ASE A1 Engine Repair Task List, Lubrication and Cooling Systems — diagnose lubrication system problems and perform oil pressure testsReport a problem with this question

15. 15. A gerotor-style oil pump is being inspected during an overhaul. How is the clearance between the inner and outer rotor tips checked?

    • A.With a dial bore gauge set across the pump housing bore diameter
    • B.With Plastigage crushed between the rotor and the pump cover
    • C.With a feeler gauge inserted between the rotor lobe tips✓ Answer
    • D.With an outside micrometer measuring the outer rotor thickness

    Tip clearance is the gap between two rotor lobes that face each other, and a feeler gauge is the tool made to measure a gap between two parallel surfaces. Plastigage reads a clearance only when a fastener crushes it, a dial bore gauge reads a hole, and an outside micrometer reads an outside dimension, so none of them can report the tip gap. The measured value is then compared with the manufacturer's specification.

    Source: ASE A1 Engine Repair Task List, Lubrication and Cooling Systems — inspect oil pump gears or rotors, housing, pressure relief devices, and pump driveReport a problem with this question

16. 16. A cylinder head is being checked for warpage after an overheating event. Which method and check pattern is correct?

    • A.A straightedge and feeler gauge, checked lengthwise and diagonally✓ Answer
    • B.A dial bore gauge swept across the deck surface at several points
    • C.A machinist rule set on edge with a light held behind the center
    • D.An outside micrometer reading head thickness at each end and the middle

    Warpage is a departure from a flat plane, so it is found by laying a precision straightedge on the deck and sliding feeler gauges under it, and the check must be run lengthwise and across both diagonals because a head can bow in one direction while reading flat in another. The largest gap found is compared with the manufacturer's flatness limit, which also governs whether the head can be resurfaced.

    Source: ASE A1 Engine Repair Task List, Cylinder Head and Valve Train — inspect cylinder head for cracks, warpage, and mating surface conditionReport a problem with this question

17. 17. A cylinder head is being installed on an engine that uses torque-to-yield head bolts. Which statement describes correct practice?

    • A.The original bolts may be reused if the threads clean up and are oiled
    • B.The bolts are tightened in stages working from the ends toward the center
    • C.The bolts are replaced, torqued in sequence in stages, then turned a set angle✓ Answer
    • D.The bolts should be re-torqued after the engine's first heat cycle

    Torque-to-yield bolts are deliberately stretched past their elastic limit to hold clamping load, so they are permanently deformed and cannot be reused or re-torqued; new bolts are installed, brought up in stages in the specified sequence, and then rotated through a specified angle with a torque-angle gauge. The tightening sequence itself always works outward from the center of the head so the gasket is not pinched at one end.

    Source: ASE A1 Engine Repair Task List, Cylinder Head and Valve Train — install cylinder head gasket and torque head bolts per the manufacturer's procedureReport a problem with this question

18. 18. A timing belt breaks while an interference-design engine is running at highway speed. The engine cranks but will not start. What should the technician expect to find?

    • A.A damaged crankshaft snout where the belt sprocket is keyed
    • B.Scored cylinder walls where the pistons struck the head deck surface
    • C.Bent valves from piston contact, so the heads must be inspected✓ Answer
    • D.Only a broken belt, since the pistons cannot reach the valves

    In an interference design the valves and pistons occupy the same space at different moments, and that separation depends entirely on the cam drive; once the belt breaks the camshaft stops while the crankshaft keeps turning, so open valves are struck by rising pistons. The heads must therefore be removed and the valves, guides, and piston crowns inspected before any belt is installed.

    Source: ASE A1 Engine Repair Task List, Cylinder Head and Valve Train — inspect cam drive components and verify valve timingReport a problem with this question

19. 19. A solid-lifter engine develops a burnt exhaust valve on one cylinder a short time after a valve adjustment. Which condition most likely caused it?

    • A.The rocker arm ratio on that cylinder was lower than on the others
    • B.The lash on that valve was set too tight, holding it off its seat✓ Answer
    • C.The valve spring installed height was left slightly above specification
    • D.The lash on that valve was set too loose, shortening the opening time

    An exhaust valve gets rid of most of its heat through contact with the seat, so lash that is too tight holds the valve slightly open as the parts expand and the valve loses its cooling path and burns. Lash that is too loose is noisy and reduces effective lift and duration, but it lets the valve close fully and therefore does not cause burning; the lash must be set to the manufacturer's specification at the specified engine temperature.

    Source: ASE A1 Engine Repair Task List, Cylinder Head and Valve Train — inspect and adjust valve lash on mechanical lifter enginesReport a problem with this question

20. 20. Plastigage is being used to check a connecting rod bearing clearance. Which procedure produces a valid reading?

    • A.Turn the crankshaft one full revolution after torquing so that the strip spreads out
    • B.Torque the cap over the dry strip without turning the crank, then read the width✓ Answer
    • C.Coat the journal and the strip with oil first so the plastic flattens evenly
    • D.Measure the length of the crushed strip against the scale on the wrapper

    Plastigage works because a soft plastic thread spreads to a width that corresponds to the gap it was squeezed into, so the journal and strip must be dry, the cap must be torqued to specification, and the crank must not be rotated, since any rotation smears the strip and gives a false narrow reading. The crushed width, not its length, is compared with the scale printed on the wrapper.

    Source: ASE A1 Engine Repair Task List, Engine Block Diagnosis and Repair — determine main and connecting rod bearing clearanceReport a problem with this question

21. 21. A cylinder bore is measured with a dial bore gauge at the top and the bottom of ring travel, and at two positions ninety degrees apart at each depth. What do those two comparisons describe?

    • A.Both comparisons describe piston-to-wall clearance at each end
    • B.Top-to-bottom difference is out-of-round, and at one depth it is taper
    • C.Top-to-bottom difference is taper, and at one depth it is out-of-round✓ Answer
    • D.Both comparisons describe the ridge worn at the top of the bore

    Taper is wear along the length of the bore, so it is the difference between the top and bottom readings, and it exists because ring load and heat are highest near the top of ring travel. Out-of-round is wear across the bore, so it is the difference between two readings taken at the same depth ninety degrees apart, and it comes mostly from side thrust; both results are compared with the manufacturer's limits to decide on boring or honing.

    Source: ASE A1 Engine Repair Task List, Engine Block Diagnosis and Repair — clean and inspect cylinder walls, measure taper and out-of-roundReport a problem with this question

22. 22. Crankshaft end play is being checked on an engine that is still assembled in the vehicle after a driveline complaint. Which setup measures it?

    • A.A dial bore gauge set into the number one main bearing bore and swept
    • B.A feeler gauge inserted between the rod cap and the counterweight
    • C.Plastigage crushed between the thrust flange and the main bearing
    • D.A dial indicator on the block reading the crank nose as it is pried✓ Answer

    End play is fore-and-aft movement of the crankshaft against its thrust surface, so it is measured by fixing a dial indicator to a stationary part of the engine with its tip on the crank nose or flange and prying the crankshaft fully one way and then the other. Excessive end play indicates a worn thrust bearing and commonly shows up as a thump or as clutch or converter engagement complaints; the reading is compared with the manufacturer's specification.

    Source: ASE A1 Engine Repair Task List, Engine Block Diagnosis and Repair — inspect crankshaft for end play and thrust surface conditionReport a problem with this question

Practice questions written to the ASE Automobile & Light Truck (A-series) task lists and standard automotive service principles. ASE is a mark of the National Institute for Automotive Service Excellence; this site is not affiliated with or endorsed by ASE. Always follow the vehicle manufacturer's service information for specifications and procedures on a real repair. About the ASE tests →