The block is the smallest A1 area, 4 scored questions, down from 10 in 2025, yet it has the longest task list: 23 tasks. With that ratio, learn what failed parts look like rather than machining figures. The questions below show a worn bearing, a damaged piston or a scored wall and ask for the cause.
4scored questions on the test
10in the 2025 edition
23tasks in the area
11questions on this page
What area C asks
From the 2026 task list, in our words:
Out and back in: remove and reinstall the engine, and prime the lubrication system before first start.
Teardown: mark the location and orientation of parts; inspect the block for cracks, warpage and passages.
Cylinders: clean and inspect the walls and bores; check the piston oil-cooling jets.
Crankshaft: end play, journals, thrust flange, keyway and the reluctor ring.
Bearings: main and rod bearing wear patterns, bores and clearances.
Cam and auxiliary shafts: cam bearings and drive, balance shaft timing.
Pistons and rods: wear patterns and rod bore condition.
Front and rear: vibration damper, flywheel or flexplate (including dual-mass) and its runout.
Assembly: pans, covers, gaskets and formed-in-place sealants; in-block VVT and cylinder deactivation.
Reading failed parts
Piston crown eroded at its outer edge: detonation, the last of the mixture igniting on its own after the spark.
A hole melted through the center of the crown: pre-ignition, the charge lit early by a glowing hot spot.
Polished top rings, low compression and fuel in the oil: fuel washdown stripped the oil film from the wall.
Scuffed walls: the oil film broke down. Fine vertical scratches mean dirt or debris rode between the piston and the wall.
Bearings wiped bright, with smeared overlay: too little oil. Embedded particles mean dirty oil instead.
Plastigage wider at one edge of the journal than the other: a tapered journal; past the limit, the crankshaft is ground and fitted with undersize bearings.
Rod bore out of shape: replace or recondition the rod, whatever the bearings look like.
Some measuring stays in the task list, including crankshaft end play, read with a dial indicator while the crank is pried fore and aft, and bearing clearance. Main caps go back in their marked places and are torqued in steps from the center outward. Cracks you can't see are found with magnetic particle inspection on iron and dye penetrant on aluminum.
11 engine block questions
0 of 11 answered · 0 correct
Question 1 of 11 · Engine Block Diagnosis and Repair · 9%Not answered
During a complete engine teardown and inspection, a technician discovers severe pitting and melting concentrated strictly around the outer edges of the piston crown and the top ring lands. The adjacent cylinder walls show no signs of scoring. What is the most likely cause of this specific damage?
Explanation
Incorrect: Foreign debris leaves dents and scratches across the crown, not erosion along the edge.
Incorrect: Normal high-mileage wear does not melt pistons.
Correct: Pitting and melting at the outer edge of the crown and the top ring land is the pressure-wave damage of detonation.
Incorrect: Oil starvation scores skirts and cylinder walls, and the walls here are clean.
Incorrect: Excessive idling leads to carbon buildup, not melted crown edges.
Question 2 of 11 · Engine Block Diagnosis and Repair · 9%Not answered
During engine teardown, a technician finds a piston with a hole melted directly through the center of its crown, while the outer ring lands remain generally intact. What is the most likely cause of this specific type of damage?
Explanation
Correct: A glowing hot spot lights the mixture early and focuses heat in the middle of the crown until a hole melts through it.
Incorrect: Detonation hammers the edges of the crown and the ring lands, not the center.
Incorrect: Extra piston-to-wall clearance causes slap and skirt wear, not a melted crown.
Incorrect: Fuel washdown strips the cylinder's oil film and scuffs it; it does not melt a hole in the piston.
Incorrect: Over-advanced timing leads to detonation and edge damage, not a hole melted through the center.
Question 3 of 11 · Engine Block Diagnosis and Repair · 9%Not answered
An engine is disassembled to diagnose a severe loss of power and poor performance. The examining technician observes heavy, localized vertical scoring on the aluminum piston skirts that perfectly matches corresponding scuff marks on the cast-iron cylinder bores. Which condition most likely caused this specific damage?
Explanation
Incorrect: A worn chain guide makes noise at the front of the engine and has nothing to do with piston-to-bore contact.
Incorrect: Retarded timing raises exhaust temperature but does not scuff pistons.
Incorrect: Exhaust backpressure lowers power but does not scuff pistons against the bore.
Correct: Matching scuff marks on the skirt and the bore mean metal touched metal, which happens only when the oil film breaks down.
Incorrect: Intake valve carbon disturbs airflow but does not scuff pistons.
Question 4 of 11 · Engine Block Diagnosis and Repair · 9%Not answered
While checking main bearing clearances with Plastigage, a technician measures 0.0030 inch at one edge of the journal and 0.0025 inch at the opposite edge. The specification is 0.0008 to 0.0022 inch. A micrometer shows that journal is under its minimum diameter and tapered. Which of the following actions is required?
Explanation
Incorrect: Polishing removes no taper and cannot bring back material that has worn away.
Incorrect: Standard bearings on an undersize, tapered journal still leave too much clearance.
Incorrect: Retorquing the caps does not change journal size, so the clearance stays out of spec.
Correct: A journal that is under size and tapered cannot be fixed with bearings alone; it has to be ground true and paired with undersize bearings.
Incorrect: A high-volume pump only masks the clearance problem and leaves the worn journal in place.
Question 5 of 11 · Engine Block Diagnosis and Repair · 9%Not answered
A vehicle has low compression on cylinder 2 and excessive fuel in the crankcase. The technician removes the piston and finds polished top ring faces and a glazed cylinder wall. What is the best explanation for the low compression?
Explanation
Incorrect: Coolant contamination leaves corrosion and residue, and the evidence here is fuel in the oil.
Incorrect: Stuck rings would show carbon packed in the ring grooves, not polished faces and glazing.
Incorrect: A coarse hone leaves rough cross-hatch, the opposite of a glazed wall.
Incorrect: Annealed rings point to overheating, which nothing in this teardown shows.
Correct: Excess fuel in the crankcase means fuel has been washing the oil film off the cylinder wall, so the rings lose their seal.
Question 6 of 11 · Engine Block Diagnosis and Repair · 9%Not answered
Which method is MOST effective for finding fine cracks in a cast-iron engine block that are not visible to the naked eye?
Explanation
Incorrect: Plain visual inspection is exactly what misses cracks too fine to see.
Incorrect: Oil spray patterns are not a crack detection method.
Correct: Magnetizing iron and dusting it with particles makes them gather along any crack, even one too fine to see.
Incorrect: A straightedge measures warpage, not cracks.
Question 7 of 11 · Engine Block Diagnosis and Repair · 9%Not answered
When checking connecting rod bearings during engine disassembly, what condition indicates the need for immediate rod replacement rather than just bearing replacement?
Explanation
Incorrect: A normal wear pattern calls for nothing beyond a bearing check.
Correct: If the big-end bore itself is distorted, new shells will not sit round, so the rod has to be replaced or reconditioned.
Incorrect: Light scoring is handled by replacing the bearing.
Incorrect: Discoloration of the bearing points to heat or lubrication trouble, but the rod bore can still be fine.
Question 8 of 11 · Engine Block Diagnosis and Repair · 9%Not answered
When checking crankshaft end play, what tool should be used?
Explanation
Incorrect: A torque wrench tightens fasteners and measures nothing about end play.
Incorrect: Plastigage measures radial oil clearance, not end play.
Incorrect: A micrometer measures journal diameter, not how far the crank moves fore and aft.
Correct: A dial indicator on the crank snout reads the fore-and-aft movement directly as the crank is pried back and forth.
Question 9 of 11 · Engine Block Diagnosis and Repair · 9%Not answered
What is the correct torque sequence for main bearing cap installation?
Explanation
Correct: Torquing from the center out lets the crank and caps settle evenly toward the ends.
Incorrect: Working from the outside in traps any misalignment in the middle caps.
Incorrect: A random order loads the caps unevenly and can bind the crank.
Incorrect: Starting at one end can pull the crank bore out of line.
Question 10 of 11 · Engine Block Diagnosis and Repair · 9%Not answered
What is the main job of the piston oil cooling jets (oil squirters) found in many engine blocks?
Explanation
Correct: The jets spray oil at the underside of each piston crown and carry heat away from the hottest part of the piston.
Incorrect: The pump primes from its pickup; the jets are fed by the pump, not the other way around.
Incorrect: The jets bleed oil out of the gallery, so they use pressure rather than raise it.
Incorrect: The cam lobes are oiled by the valve train supply; the jets aim at the pistons.
Question 11 of 11 · Engine Block Diagnosis and Repair · 9%Not answered
A technician notices coolant seeping through an aluminum engine block without visible external cracks. What is the most likely cause of this condition?
Explanation
Incorrect: A failed core plug leaks at the plug itself, not through the casting.
Correct: Tiny voids left in the aluminum when it was cast can weep coolant straight through the wall, with no crack to see.
Incorrect: A water pump seal leaks at the pump's weep hole, not through the block.
Incorrect: A head gasket leaks at the joint between head and block, not through the block wall.
Answer every question to see your score
What the 2026 list dropped here
Piston, pin and piston-ring measuring tasks were dropped. Cylinder bore and crankshaft journal measuring became inspection tasks. A pre-2026 book that spends pages on ring end gap is preparing you for questions the 2026 test is no longer written to.
4 of the 45 scored questions in 2026, the fewest of the five areas.
What causes a hole in the center of a piston?
Pre-ignition: a hot spot, such as a glowing deposit or an overheated plug tip, lights the mixture before the spark and concentrates heat in the middle of the crown. Detonation damage starts at the edge instead.
How do you check crankshaft end play?
Mount a dial indicator against the end of the crankshaft, pry it fully rearward, zero the gauge, then pry it forward and read the travel. Compare with the specification; too much points to a worn thrust bearing or thrust surfaces.