Deck 54: Engine Diagnosis and Service: Piston, Piston Rings, Connecting Rod, Engine Balancing

Question 1

Excessive heat can cause ____________________, which occurs when the cylinder wall and piston momentarily weld to each other when the piston stops at TDC.

Answer 1

scuffing

Question 2

Damaging a metal surface raises stress, weakening the part. This is called a(n) "____________________."

Answer 2

stress raiser

Question 3

All of the following statements are true EXCEPT:

A)machinists use a pin press to separate pressed-fit pins and pistons from their connecting rods.
B)pistons have a notch on the side of the piston head that faces the front of the engine.
C)always soak a piston and rod assembly in a chemical cleaner.
D)reinstallation is done using a rod heater to heat the eye of the rod.

Answer 3

C

Question 4

Pistons should be chemically cleaned while assembled to the piston pin and connecting rod.

Question 5

All of the following statements are true EXCEPT:

A)correcting dynamic imbalance can result in the correction of force imbalance at the same time.
B)primary vibrations are only about one-fourth of the strength of secondary vibrations but can become quite severe at the higher rpm at which four-cylinder engines quite often operate.
C)computer balancers compute the combined amount of dynamic and force imbalance and tell where to remove metal to correct them.
D)balance shafts are used to cancel out secondary vibration.

Question 6

Whenever an engine is disassembled, the piston rings are replaced.

Question 7

Which of the following statements is LEAST-Likely true?

A)Scuffing on only one skirt is rarely caused by excessive idling.
B)Four-corner scuffing occurs when both skirts are scuffed on the edges next to the piston pin.
C)A piston that overheats because of cooling system problems or abnormal combustion will expand excessively near the piston pin.
D)Scuffing on both skirts is usually caused by insufficient clearance between new pistons and remachined cylinder walls.

Question 8

Which of the following statements is LEAST-Likely true?

A)As the engine operates, rings will rotate from the position where they were first installed.
B)End gap position is one of the causes of oil consumption.
C)If an engine has operated for 100,000 miles or more without an unusual wear problem, the rod can safely be reused with new bearing inserts.
D)A bent rod will show wear on opposite sides of the rod bearings.

Question 9

Compression rings are removed using a(n) ____________________.

Question 10

While having a discussion, Technician A says that balance is not as important with V-type engines, but it is critical with in-line engines. Technician B says that balance is not as important with in-line engines, but it is critical in V-type engines. Who is correct?

A)A only
B)B only
C)Both A and B
D)Neither A nor B

Question 11

Modern aluminum pistons have high silicon content that causes them to wear out the piston ring.

Question 12

Internal balancing of forged cranks is MOST-Likely achieved by drilling holes on the:

A)connecting rods
B)bob weights
C)ring groove
D)counterweights

Question 13

To maintain engine balance, a new replacement piston's weight should match that of the original piston.

Question 14

When a replacement piston is heavier than the others, it can be lightened at the ____________________.

Question 15

When the piston slows down as it approaches TDC, its force pulls the engine up. When it approaches BDC, it pulls the engine down. This is known as ____.

A)primary vibration
B)end gap
C)rocking couple
D)stress raising

Question 16

While having a discussion, Technician A says that replacement pistons for passenger cars and light trucks are destroked 0.15" to compensate for block and head resurfacing. Technician B says that they are destroked at 0.25". Who is correct?

A)A only
B)B only
C)Both A and B
D)Neither A nor B

Question 17

An increase of 0.002" in the bore size will increase the gap by about 0.016".

Question 18

The parts that are MOST-Likely used when spinning the crankshaft to simulate the correct weight are:

A)bob weights
B)counterweights
C)ring grooves
D)plugs

Question 19

____, also called static or kinetic imbalance, can be compared to the type of imbalance that is corrected when balancing tires with a bubble (level) balancer.

A)End gap
B)Vibration imbalance
C)Scuffing
D)Force

Question 20

____________________ is done when a rod bearing has burned or if the big end has stretched.

Question 21

When inspecting piston rings for wear, what should you look for?

Question 22

What causes piston ring wear?

Question 23

Why is it a bad idea to overtighten rod bolts?

Question 24

How would you resize a rod?

Question 25

If a customer complains about engine vibration, where would you begin your investigation and why?