Engine Repair Flashcards

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

Answer: Grinding valve stems

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.

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?

Answer: X only

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.

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:

Answer: Inspect the pulleys for signs of excess play or bearing noise

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.

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

Answer: Timing belt tension too loose

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.

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?

Answer: Piston slap

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.

An idle vacuum test is carried out by a technician. The 2001 Sedan's test results show a pressure of 11 in. Hg. What should the technician check next?

Answer: Check for proper timing

An idle vacuum reading of 11 in. Hg is significantly lower than the normal range (typically 17-21 in. Hg at sea level), indicating a potential engine problem. Low vacuum can be caused by several issues, but incorrect ignition timing (retarded timing) is a common cause that directly affects engine efficiency and vacuum production. Checking timing is a logical and relatively easy diagnostic step to perform next.

While cleaning the pleated paper-type air filter element, the air gun should be held:

Answer: Away from the inside of the air filter element.

When cleaning a paper air filter with compressed air, the air should be blown from the *inside out* to push trapped dirt particles away from the clean side. Holding the air gun *away* from the inside allows the air to expand and gently dislodge particles without damaging the delicate filter media. Blowing from the outside in or holding the gun too close can embed dirt deeper or tear the filter.

When doing an engine compression test, you must disable the fuel injection, ignition systems and all of the following reasons, except:

Answer: Prevents inaccurate readings

Disabling the fuel injection and ignition systems during a compression test is primarily done to prevent fuel from entering the cylinders (which could wash down cylinder walls or create a fire hazard) and to prevent the ignition system from firing (which could damage components or cause a shock). It does not directly prevent inaccurate readings; rather, it ensures safety and prevents secondary issues that could complicate the test. Accurate readings are achieved by following the correct test procedure, not by disabling these systems for accuracy itself.

A power balance test is being performed on an engine. Technician X says to note the engine RPM before and during the test for each cylinder. Technician Y says to record the RPM drop for each cylinder. Who is right?

Answer: Both X and Y

Both technicians are correct. A power balance test involves individually disabling cylinders and observing the resulting RPM drop. Technician X's approach of noting RPM before and during the test is necessary to calculate the RPM drop. Technician Y's instruction to record the RPM drop is the direct measurement used to compare the power contribution of each cylinder. Both steps are integral to accurately performing and interpreting a power balance test.

An air leak within the cylinder is what you're searching for when performing an engine compression test. This test will reveal air leaks in all of the following, with the exception of which?

Answer: PCV valve

An engine compression test measures the ability of a cylinder to hold pressure, thereby revealing leaks past the piston rings, intake/exhaust valves, or the cylinder head gasket. The PCV (Positive Crankcase Ventilation) valve is part of the crankcase ventilation system and is external to the combustion chamber's sealing integrity during a compression test. While a faulty PCV valve can cause vacuum leaks, it does not directly affect the compression within the cylinder itself.

What might happen if new rings are installed without removing the ring ridge?

Answer: The piston ring or top compression ring may crack or break

A ring ridge is a wear step at the top of the cylinder bore, above the travel of the top piston ring. If new rings are installed without removing this ridge, the top compression ring will hit it during upward piston travel. This impact can cause the new, sharp-edged ring to crack, break, or become severely damaged, leading to immediate compression loss and engine failure.

Technician X says the closed coil end of a valve spring should go against the cylinder head. Technician Y says all valve springs use shims to control free spring height. Who is right?

Answer: X only

Technician X is correct. Valve springs often have a 'closed' or tighter wound coil end, which is designed to be placed against the cylinder head or spring seat. This helps reduce spring resonance and provides a more stable base. Technician Y is incorrect; not all valve springs use shims. Shims are used when necessary to adjust spring installed height and tension to specification, but they are not universally required for every valve spring application.

Technician X says old antifreeze may cause corrosion build-up in the cooling system. Technician Y says some original equipment manufacturers (OEM) recommend that the coolant be changed at specified intervals. Who is right?

Answer: Both X and Y

Both technicians are correct. Over time, the corrosion inhibitors in antifreeze deplete, allowing rust and other deposits to form, which can damage cooling system components. Therefore, OEMs specify regular coolant change intervals to maintain proper corrosion protection and ensure optimal cooling system performance. Neglecting these intervals can lead to significant engine damage.

A customer complains about white smoke coming from the exhaust system. You should start by checking which system for low fluid levels?

Answer: Cooling System

White smoke from the exhaust typically indicates that coolant is entering the combustion chambers and being burned. This is often a symptom of a leaking head gasket or a cracked cylinder head. Therefore, checking the cooling system for low fluid levels is the most logical first step to confirm if coolant is being consumed, which would support this diagnosis.

Technician X says a special puller and installer tool is required to remove and install the vibration damper. Technician Y says that if the intertia ring on the vibration damper is loose, the damper must be replaced. Who is right?

Answer: Both X and Y

Both technicians are correct. Vibration dampers (harmonic balancers) are often press-fit onto the crankshaft, requiring specialized pullers and installers to prevent damage during removal and installation. Furthermore, the inertia ring, which is crucial for dampening engine vibrations, is bonded to the hub. If this bond fails and the inertia ring becomes loose, the damper's effectiveness is compromised, and it must be replaced to prevent excessive engine vibration and potential damage.

When adjusting valve lash on engines with overhead camshaft cylinder heads, all of the following statements are correct, EXCEPT:

Answer: The engine must be cold for all engine manufacturers

While many manufacturers specify valve lash adjustments on a cold engine, it is not universally true for *all* engine manufacturers. Some engines, particularly older designs or specific performance applications, may require hot adjustments to account for thermal expansion. Therefore, stating that the engine *must* be cold for *all* manufacturers is an incorrect generalization.

In the illustration, what engine seal is shown?

Answer: Valve

Assuming the illustration shows a valve stem seal, this component is a small rubber or synthetic seal that fits around the valve stem. Its purpose is to prevent engine oil from leaking down the valve guide into the combustion chamber, which helps control oil consumption and prevents carbon buildup on the valves. This is a critical seal for the engine's proper operation.

Which components inside the valve train are most likely to create a significant amount of excess engine noise?

Answer: Worn or dirty rocker arms

Worn or dirty rocker arms, especially their pivots or contact surfaces with the valve stem or pushrod, can lead to excessive valve lash. This increased clearance causes a distinct ticking or tapping noise as the components impact each other with greater force. Other valve train components can also cause noise, but worn rocker arms are a very common source of noticeable engine noise.

When pressing the wrist pin into the piston and connecting rods, which of the following steps is the technician LEAST likely to perform?

Answer: Heat the wrist pin

For press-fit wrist pins, it's common practice to heat the small end of the connecting rod. This causes the rod's bore to expand, allowing the wrist pin to be pressed in more easily and securely. Heating the wrist pin itself would cause it to expand, making it *harder* to press into the rod, which is the opposite of the desired effect. Proper orientation and alignment are also critical steps.

Below are the following ways the piston is attached to the rod, EXCEPT:

Answer: Woodruff key

Pistons are typically attached to connecting rods via a wrist pin (also called a gudgeon pin) using one of three common methods: press-fit to the piston, press-fit to the rod, or free-floating (secured by circlips). A Woodruff key is a crescent-shaped key used to secure components like gears or pulleys to a shaft, preventing rotational movement, and is not used in piston-to-rod attachment.