Question 1

An engine is disassembled because of a single torched piston: the other five appear normal. Which of the following should be investigated first?
A) failed head gasket fire ring
B) oil cooling jet
C) water jacket scaling
D) connecting rod oil rifle

Accepted Answer

B

Question 2

When an engine is disassembled, all of the pistons show some evidence of lacquering. Which of the following is the more likely cause?
A) high temperature operation
B) low temperature operation
C) high sulfur fuel
D) failed oil control rings

Accepted Answer

High sulfur fuel can cause lacquering on pistons.

Question 3

When piston rings stick by gumming, what is a common cause?
A) high engine temperatures
B) coolant in combustion process
C) prolonged idling
D) prolonged lugdown

Accepted Answer

D

Question 4

When evidence of lacquering is found on a set of crankshaft main bearings, which of the following operating and maintenance practices should be examined first?
A) quality of engine lubricating oil
B) quality of fuel
C) frequency of oil change intervals
D) frequency of bearing rollovers

Accepted Answer

Lacquering on crankshaft main bearings is often related to the quality of the engine lubricating oil, as poor quality oil can lead to deposits forming on the bearings.

Question 5

If a dry sleeve designed for a 0.0015 inch (0.038 mm) loose fit is installed to the engine block with insufficient clearance, which of the following will more likely result?
A) liner will last longer
B) liner failure due to higher cylinder pressures
C) premature liner failure due to buckling
D) cracked liners

Accepted Answer

Premature liner failure due to buckling is more likely because insufficient clearance does not allow for proper expansion and contraction of the liner, leading to mechanical stress and eventual buckling.

Question 6

When a set of wet liners has evidence of severe cavitation, which of the following maintenance and operating practices should be investigated first?
A) idle shutdown duration programming
B) road speed governing
C) type of antifreeze used and service intervals
D) type of engine oil used and service intervals

Accepted Answer

Cavitation is often related to the type of antifreeze used and its service intervals, as improper coolant or lack of maintenance can lead to cavitation damage on wet liners.

Question 7

When a piston fails due to cracks in the cavity edge of the Mexican hat recess, the usual cause would be:
A) high cylinder pressures
B) overheating
C) cold weather operation
D) injector dribble

Accepted Answer

The answer of When a piston fails due to cracks...

Question 8

When it is determined that a crankshaft has a torsional failure, all of the following should be balance-checked EXCEPT:
A) water pump
B) engine fan
C) vibration damper
D) flywheel

Accepted Answer

The water pump is not directly related to the balance of the crankshaft as it is not part of the rotating assembly that directly affects the crankshaft's balance. Components like the engine fan, vibration damper, and flywheel are directly involved in the balance and vibration control of the crankshaft.

Question 9

Which of the following must be located during failure analysis investigation if a repeat is to be avoided?
A) coincidental damage
B) warranty report
C) policy adjustment
D) root cause

Accepted Answer

The root cause of a failure must be identified and understood in a failure analysis investigation to prevent the issue from recurring. Identifying the root cause helps in addressing the fundamental issue rather than just treating symptoms.

Question 10

When performing failure analysis on engine components, the technician is required to have an understanding of which of the following?
A) wear patterns
B) basic metallurgy
C) fractures
D) all of the above

Accepted Answer

Understanding wear patterns, basic metallurgy, and fractures are all crucial for performing failure analysis on engine components, as they help in identifying the cause of failure and preventing future occurrences.

Question 11

Technician A says that a keyway cut into a shaft is a potential stress raiser. Technician B says that oil holes in crankshafts are potential stress raisers. Who is correct?
A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Accepted Answer

Both keyways and oil holes introduce changes in the material's continuity, creating points where stress can concentrate, potentially leading to failure under certain conditions.

Question 12

Technician A says that when a component fails due to a metallurgical defect, the technician is at fault. Technician B says that a casting inclusion in a cylinder head can be classified as a metallurgical defect. Who is correct?
A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Accepted Answer

Technician B is correct because a casting inclusion in a cylinder head is indeed a type of metallurgical defect, which occurs during the manufacturing process and is not the fault of the technician.

Question 13

Technician A says that visual inspection is one of the most important factors of good failure analysis practice. Technician B says that laboratory analysis is usually required to accurately pinpoint root cause. Who is correct?
A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Accepted Answer

The answer of Technician A says that visual inspection is...

Question 14

When adhesive wear occurs on crankshaft main bearing, which of the following would be the more likely cause?
A) Inappropriate lube oil
B) Prolonged high load operation
C) Prolonged low load operation
D) Irregular align bore

Accepted Answer

Inappropriate lube oil can lead to insufficient lubrication, causing metal-to-metal contact and adhesive wear on the crankshaft main bearing.

Question 15

Technician A says that most corrosion deterioration on engine metals is related to acids in degraded engine lube. Technician B says that most corrosion wear on engine components is either directly or indirectly related to oxidation. Who is correct?
A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Accepted Answer

The answer of Technician A says that most corrosion deterioration...

Question 16

When two metal components clamped by fasteners are allowed to move against each other, the result is:
A) impact damage
B) stress damage
C) fretting damage
D) fatigue damage

Accepted Answer

When two metal components clamped by fasteners are allowed to move against each other, the result is fretting damage. This occurs due to the small amplitude oscillatory motion that causes wear and sometimes corrosion at the surface, leading to material degradation.

Question 17

Which of the following is another way of saying ductile?
A) brittle
B) flexible
C) fractured
D) abrasive

Accepted Answer

Ductile refers to the ability of a material to deform under tensile stress, typically stretching into a wire, which is closely related to being flexible.

Question 18

Which type of crankshaft fracture failure would result from an excessive shock load?
A) brittle fracture
B) ductile fracture
C) fatigue fracture
D) compressional fracture

Accepted Answer

Brittle fracture is the type of crankshaft fracture failure that would result from an excessive shock load. This is because brittle fracture occurs suddenly and without significant deformation, as would be the case when a crankshaft is subjected to a sudden and extreme load.

Question 19

You are inspecting a crankshaft fracture in which the fracture faces appear relatively smooth with evidence of beach marks. What type of fracture would be the likely diagnosis?
A) brittle
B) ductile
C) fatigue
D) metallurgical defect

Accepted Answer

Fatigue fractures are characterized by the presence of beach marks, which are indicative of the progressive nature of the crack growth under cyclic loading. These marks appear as concentric ridges or patterns on the fracture surface, revealing the history of the crack propagation.

Question 20

When a head gasket coolant leak causes a hydraulic lock in one cylinder, which of the following would be the more likely result?
A) fractured piston crown
B) fractured main bearing cap
C) connecting rod tensional failure
D) connecting rod compressional failure

Accepted Answer

Connecting rod compressional failure is more likely because the hydraulic lock creates a situation where the incompressible coolant prevents the piston from moving properly. This puts excessive compressive force on the connecting rod, which can lead to its failure.

Quiz 51: Failure Analysis

An engine is disassembled because of a single torched piston: the other five appear normal. Which of the following should be investigated first?

When an engine is disassembled, all of the pistons show some evidence of lacquering. Which of the following is the more likely cause?

When piston rings stick by gumming, what is a common cause?

When evidence of lacquering is found on a set of crankshaft main bearings, which of the following operating and maintenance practices should be examined first?

If a dry sleeve designed for a 0.0015 inch (0.038 mm) loose fit is installed to the engine block with insufficient clearance, which of the following will more likely result?

When a set of wet liners has evidence of severe cavitation, which of the following maintenance and operating practices should be investigated first?

When a piston fails due to cracks in the cavity edge of the Mexican hat recess, the usual cause would be:

When it is determined that a crankshaft has a torsional failure, all of the following should be balance-checked EXCEPT:

Which of the following must be located during failure analysis investigation if a repeat is to be avoided?

When performing failure analysis on engine components, the technician is required to have an understanding of which of the following?

Technician A says that a keyway cut into a shaft is a potential stress raiser. Technician B says that oil holes in crankshafts are potential stress raisers. Who is correct?

Technician A says that when a component fails due to a metallurgical defect, the technician is at fault. Technician B says that a casting inclusion in a cylinder head can be classified as a metallurgical defect. Who is correct?

Technician A says that visual inspection is one of the most important factors of good failure analysis practice. Technician B says that laboratory analysis is usually required to accurately pinpoint root cause. Who is correct?

When adhesive wear occurs on crankshaft main bearing, which of the following would be the more likely cause?

Technician A says that most corrosion deterioration on engine metals is related to acids in degraded engine lube. Technician B says that most corrosion wear on engine components is either directly or indirectly related to oxidation. Who is correct?

When two metal components clamped by fasteners are allowed to move against each other, the result is:

Which of the following is another way of saying ductile?

Which type of crankshaft fracture failure would result from an excessive shock load?

You are inspecting a crankshaft fracture in which the fracture faces appear relatively smooth with evidence of beach marks. What type of fracture would be the likely diagnosis?

When a head gasket coolant leak causes a hydraulic lock in one cylinder, which of the following would be the more likely result?