ASE A1 Engine Repair Practice Test
51. A compression test indicates the number one cylinder's compression is below specifications. The compression increases after injecting oil into the cylinder. Which of the following is causing this test result?
- A. Worn piston rings.
- B. A faulty intake valve.
- C. A faulty head gasket.
- D. A faulty exhaust valve.
Answer A is correct. If compression increases after injecting oil into the cylinder, the piston rings are worn. The oil fills the gap caused by the worn rings increasing the cylinder's compression.
Answer B is wrong. If there is no change in compression after adding oil, perform a cylinder leakage test to check for a faulty valve.
Answer C is wrong. If there is low compression in two adjacent cylinders, suspect a faulty head gasket leaking compression between the two.
Answer D is wrong. Exhaust valves run hotter and burn more frequently than the intake valves do. They do not benefit from the fresh air /fuel charge that the intake valve receives.
52. A vehicle has blue-gray colored exhaust emitting from its tailpipe. All of the following results in this condition EXCEPT:
- A. Worn piston rings.
- B. A leaking fuel injector.
- C. Leaking valve seals.
- D. A clogged PVC valve.
Answer A is wrong. A wet cylinder compression test indicates if it's a valve or the piston rings, causing the blue exhaust. If the compression has increased, it's because the weak seal between the piston rings and the cylinder wall has been filled with oil.
Answer B is correct. A leaking fuel injector results in black-colored exhaust from the excess fuel burning in the combustion chamber.
Answer C is wrong. Leaking valve seals allow the oil to seep into the cylinders overnight, resulting in blue-colored exhaust in the morning.
Answer D is wrong. A clogged, faulty, or closed PVC valve results in excessive crankcase pressure forcing oil past the piston rings and into the chamber.
53. A ridge has formed on an engine block just above the piston ring's travel. Which of the following is used to remove this ridge?
- A. A cylinder ridge reamer.
- B. A flexible beaded hone.
- C. Both A and B
- D. Neither A or B
Answer A is correct. When removing a piston from the engine block, it's best to remove the cylinder's ridge before removing the piston. The ridge occurs as the cylinder wall wears and appears just above the top compression ring. Use a ridge reamer to remove this ridge.
Answer B is wrong. Use a flexible stone or a beaded hone to remove the glaze and restore the cylinder's finish. Move the hone up and down at a consistent speed to create a cross-hatch finish. When finished, carefully clean the cylinder and engine block with soap and water to remove any left over debris.
Answer C is wrong. Be careful; it's easy to remove too much material from a cylinder. Follow the tool manufacturer's procedure and do this process in small increments, so valuable surface is not removed.
Answer D is wrong. Removing the ridge prevents damage to the piston ring groove lands during piston removal.
54. A vehicle briefly blows blue-gray exhaust smoke from its tailpipe only in the morning or after it's been sitting for a while. Which of the following is causing this condition?
- A. A leaking cylinder head gasket.
- B. Leaking valve stem seals.
- C. A leaking fuel injector.
- D. Worn piston rings.
Answer A is wrong. A leaking cylinder head gasket results in white-colored exhaust. Coolant is leaking from the coolant jacket past the gasket and into the combustion chamber.
Answer B is correct. When valve seals leak, oil enters the combustion chamber causing the vehicle to emit blue-gray exhaust from its tailpipe. The exhaust smoke is most apparent at start-up after the vehicle's been sitting for a while.
Answer C is wrong. A rich fuel condition caused by leaking fuel injectors results in black-colored smoke emitting from the tailpipe.
Answer D is wrong. Worn piston rings would result in blue-gray smoke at all times, not just in the mornings.
55. An engine's radiator hose collapses as the engine cools. Which of the following is MOST likely causing this condition?
- A. Low coolant level.
- B. A stuck closed thermostat.
- C. A faulty radiator cap.
- D. A leaking heater core.
Answer A is wrong. An insufficient coolant level results in engine overheating.
Answer B is wrong. A stuck closed thermostat also results in engine overheating.
Answer C is correct. A faulty radiator cap vacuum valve can stick, resulting in an excessive vacuum in the system. This problem results in a collapsed radiator hose as the vacuum pulls the walls of the hose inward.
Answer D is wrong. A leaking heater core results in coolant leaking onto the passenger's floorboard/carpet.