To clear liquid lock in a cylinder, which action is performed?

• A. Remove one of the spark plugs and turn the crankshaft until all of the oil is forced out of the cylinder.
• B. Drain the cooling system and refill with fresh coolant.
• C. Inject solvent into the spark plug hole to dissolve oil.
• D. Flash the cylinder with compressed air to remove oil.

Answer: (A)

When a cylinder has liquid in it, it becomes hydraulically locked and the piston can’t move. To clear this, remove a spark plug from that cylinder and rotate the crankshaft until the liquid is pushed out through the spark plug hole. Do this slowly and with the ignition off, so you don’t crank the engine with a misfire or start it accidentally. The spark plug hole gives a direct vent for the liquid as the piston moves, allowing the cylinder to be cleared.

Other options don’t address the locked liquid: draining the cooling system doesn’t affect the oil or fuel in the cylinder, injecting solvent can contaminate the engine and cause damage, and using compressed air can push the liquid somewhere unintended or cause harm.