ASE Practice Test (A1: Engine Repair)

Question 1

The cylinder head's surface has just been machined. What will have to do to the valve train?

Accepted Answer

Grinding valve stems

Answer

Machining the cylinder head surface removes material, effectively lowering the head and bringing the valves closer to the camshaft/rocker arms. This reduction in height can cause the valve stems to protrude too far, leading to incorrect valve lash or even coil bind. Grinding the valve stems shortens them, restoring proper valve train geometry and ensuring correct valve operation after the head has been resurfaced.

Question 2

A cylinder leakage test is used to diagnose an engine miss. Technician X says that any cylinder with over 20 percent leakage has excessive leakage. Technician Y says that air leaking from the tailpipe indicates a cracked cylinder head. Who is right?

Accepted Answer

X only

Answer

Technician X is correct because a leakage rate exceeding 20% is generally considered excessive and indicates a significant problem within that cylinder, such as worn rings or valve issues. Technician Y is incorrect; air leaking from the tailpipe during a cylinder leakage test typically indicates a leaking exhaust valve, not necessarily a cracked cylinder head. A cracked cylinder head would more likely show leakage into the cooling system or an adjacent cylinder.

Question 3

The engine is making a rattling noise, according to a client. It's coming from the drive belt/serpentine belt system, according to Technician A. The following step is to:

Accepted Answer

Inspect the pulleys for signs of excess play or bearing noise

Answer

If a rattling noise is identified as coming from the drive belt system, the next logical step after initial diagnosis is to pinpoint the exact source. Pulleys with excessive play or worn bearings are common culprits for rattling or squealing noises in the serpentine belt system. Inspecting them directly helps identify the failing component before simply replacing parts.

Question 4

Which of the following causes a flapping noise near the front of the engine?

Accepted Answer

Timing belt tension too loose

Answer

A loose timing belt can cause a flapping or slapping noise because it has too much slack and can whip around as the engine operates. This excessive movement can lead to the belt hitting components or simply creating noise due to its uncontrolled motion. Proper tension is critical for the timing belt's quiet and efficient operation.

Question 5

When the engine is cold, an engine noise sounds like a knock on the side of the engine. When the engine achieves operational temperature, the noise goes gone or is lessened. Which of the following is the MOST LIKELY reason for the problem?

Accepted Answer

Piston slap

Answer

Piston slap occurs when there's excessive clearance between the piston skirt and the cylinder wall, especially when the engine is cold. As the engine warms up, the pistons expand more than the cylinder walls, reducing this clearance and causing the knocking noise to diminish or disappear. This characteristic behavior is a classic symptom of piston slap.