Crankshaft Failures and Causes

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What is the primary cause of crankshaft failures?

Incorrect loading or lubrication problems (correct)
Materials used in construction
Poor maintenance of the engine
Normal wear and tear of the engine

What can excessive bending loads on a crankshaft cause?

Increased engine performance
Improved lubrication
Crankshaft breakage (correct)
Reduced engine noise

What is a common cause of bending loads on a crankshaft?

Faulty spark plugs
Misalignment of the main bearing bores (correct)
Worn-out piston rings
Clogged air filter

What type of load is most likely to cause a break in the connecting rod journal area?

Torsional load (C) Signup and view all the answers

What is a potential consequence of running with excessive clearance in the bearings?

Bending loads on the crankshaft (D) Signup and view all the answers

Why is it important to perform a close inspection after a crankshaft failure?

To determine the cause of the failure (A) Signup and view all the answers

What is the primary cause of the wiping action that wears the surface of the bearing?

Fuel dilution of the engine oil (C) Signup and view all the answers

What is the primary cause of acid formation in the lubricating oil?

Combustion by-products from the fuel (C) Signup and view all the answers

What is the primary effect of fuel dilution on the engine oil?

Reduces the viscosity of the engine oil (D) Signup and view all the answers

What is the primary cause of corrosive damage to the bearings?

Combustion by-products from the fuel (B) Signup and view all the answers

What is the primary cause of metal fatigue in the bearings?

Overloading of the engine (A) Signup and view all the answers

What is the primary effect of coolant contamination on the bearings?

Forms organic acids that attack the bearing material (B) Signup and view all the answers

What is a common cause of crankshaft failure due to machining practices?

Improper grinding of the fillet radius (A) Signup and view all the answers

What is the recommended minimum undersize for crankshaft journals?

0.030" (0.75 mm) (C) Signup and view all the answers

What is a consequence of a lack of lubrication on crankshaft journals?

Metal to metal contact and scoring (D) Signup and view all the answers

What is a common source of contamination in the lubricating oil?

All of the above (D) Signup and view all the answers

What is a characteristic of normal bearing wear?

Exposure of the copper inner layer (B) Signup and view all the answers

What is a consequence of contaminated lubricating oil?

Accelerated wear or damage to crankshaft journals (B) Signup and view all the answers

What is a cause of bearing failure?

Breakdown or loss of the oil film (A) Signup and view all the answers

What is a consequence of a lack of lubrication on bearings?

Rapid destruction of the bearings (B) Signup and view all the answers

What is a source of foreign material in the lubricating oil?

Poor maintenance practices (C) Signup and view all the answers

What is a characteristic of bearing damage due to foreign particle contamination?

Abrasive wear or deep scratches (B) Signup and view all the answers