Engine Systems and Repair Flashcards

What is the purpose of the valley pan (lifter valley cover) in a V-type engine?

Answer: To seal the lifter valley from oil leaks and prevent oil from pooling around intake components

The valley pan seals the area between the cylinder banks (lifter valley), preventing oil splash from contaminating the intake manifold area and acting as a gasket surface.

What is the primary reason for performing an engine oil analysis?

Answer: To detect wear metals, contaminants, and fluid breakdown for predictive maintenance

Oil analysis identifies wear metals (iron, copper, aluminum), coolant contamination, fuel dilution, and additive depletion, enabling early detection of developing problems before catastrophic failure.

When setting valve lash on an engine with solid lifters, what is the piston position for the cylinder being adjusted?

Answer: Top dead centre on the compression stroke

Valve lash is set at TDC of the compression stroke because both valves are fully closed at this point, allowing accurate measurement of the clearance between the rocker arm and valve stem tip.

What causes detonation (engine knock) in a gasoline engine?

Answer: Uncontrolled auto-ignition of the end gases ahead of the flame front

Detonation occurs when heat and pressure cause the unburned air-fuel mixture ahead of the normal flame front to spontaneously ignite, creating a secondary pressure wave that collides with the primary wave, producing the knock sound.

What is the purpose of the Woodruff key on a crankshaft?

Answer: To index and prevent rotation of components like the timing sprocket on the crankshaft

The Woodruff key is a half-moon shaped key that fits into a slot on the crankshaft, preventing components like the timing sprocket or gear from rotating independently of the crankshaft.

A technician observes that coolant is disappearing with no visible leaks. A combustion gas test of the radiator is positive. What is the diagnosis?

Answer: Internal head gasket leak allowing combustion gases into the cooling system

A positive combustion gas test (block test) at the radiator indicates that combustion gases are entering the cooling system through a breached head gasket, causing coolant to be consumed in the combustion chamber.