Engine Repair and Performance Flashcards

A cylinder leakage test shows 30% leakage on cylinder 3, and air can be heard escaping from the oil fill cap. What is the most likely cause?

Answer: Worn piston rings or cylinder wall

Air escaping through the crankcase (oil fill or PCV) indicates leakage past the piston rings.

During a cylinder leakage test, air is heard escaping from the throttle body. Which component is most likely at fault?

Answer: Intake valve

Air exiting through the intake system means the intake valve is not sealing.

A wet compression test raises a low cylinder reading significantly. What does this indicate?

Answer: Worn piston rings

Oil temporarily seals worn rings, so compression rises when rings are the problem.

An engine vacuum gauge reading fluctuates rhythmically between 14 and 18 in. Hg at idle. Technician A says this can indicate a burned or sticking valve. Technician B says it indicates a restricted exhaust. Who is correct?

Answer: Technician A only

A regular rhythmic drop points to a valve problem, while exhaust restriction causes vacuum to slowly fall with rpm.

Which tool is used to measure cylinder bore taper and out-of-round?

Answer: Dial bore gauge

A dial bore gauge measures bore diameter at multiple points to determine taper and out-of-round.

An engine produces blue smoke on startup after sitting overnight, then the smoke clears. What is the most likely cause?

Answer: Worn valve guide seals

Oil seeps past worn valve stem seals while the engine sits and burns off at startup.

What is the purpose of a torque-to-yield (TTY) cylinder head bolt?

Answer: It is stretched into its elastic/plastic range for consistent clamping force

TTY bolts are stretched past their yield point for precise clamp load and are normally replaced, not reused.