Engine Repair and Diagnosis Flashcards
7 cards from real NAPA practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Engine Repair and Diagnosis flashcards as text
A cylinder reads 95 psi on a dry compression test and 140 psi after adding a teaspoon of oil. What is the most likely cause?
Answer: Worn or stuck piston rings
Oil temporarily seals worn rings, so a large rise on the wet test points to ring or cylinder wall wear.
Two adjacent cylinders both show low compression of similar values while all others are normal. What is the most likely cause?
Answer: Head gasket failure between the two cylinders
A gasket breach between neighboring cylinders lets pressure escape from one to the other, lowering both.
During a cylinder leakage test, air is heard escaping from the oil filler opening. Where is the leak?
Answer: Piston rings
Air passing the rings enters the crankcase and exits through the oil fill or PCV openings.
During a leak-down test, air is heard hissing at the throttle body. Which component is leaking?
Answer: Intake valve
A leaking intake valve sends air back into the intake manifold and out the throttle body.
Air escaping from the tailpipe during a cylinder leakage test indicates which problem?
Answer: Leaking exhaust valve
A poorly sealing exhaust valve lets test air pass into the exhaust system.
Bubbles appear in the radiator filler neck while a cylinder is under leak-down test pressure. What does this indicate?
Answer: Head gasket leak or cracked head/block
Combustion-chamber air reaching the coolant means a breach through the head gasket or a crack.
What is the generally accepted maximum variation between the highest and lowest cylinder compression readings on a healthy engine?
Answer: About 10%
Most manufacturers consider readings within roughly 10% of each other acceptable.