Start Searching the Answers
The Internet has many places to ask questions about anything imaginable and find past answers on almost everything.
Crankshaft failures may be resulted from by several causes which are oil absence, defective lubrication on journals, high operating oil temperature, misalignments, improper journal bearings or improper clearance between journals and bearings, vibration, high stress concentrations, improper grinding, high surface …
Some types of mechanical failure mechanisms are: excessive deflection, buckling, ductile fracture, brittle fracture, impact, creep, relaxation, thermal shock, wear, corrosion, stress corrosion cracking, and various types of fatigue.
Most of engine bearing failures are caused by one of the two factors: – Mixed lubrication with direct metal-to-metal contact between the bearing and crankshaft surfaces; – Fatigue of the bearing material. Mixed lubrication is one of the main causes of engine bearing failures.
In many cases, a bad rod bearing will lead to a “check engine oil” light being displayed on the dash. However, depending upon the severity of the problem with the bearing, the light may or may not go out after the engine runs for a few minutes.
While it may seem like common sense, standard wear and tear is one of the leading causes of bearing failure. Eventually all bearings fail due to wear, however, excessive load, vibration or force can cause a bearing to wear out long before it should. Most of this excess force is caused by improper installation.
Consider these six actions you can take now to prevent a bearing — and process — failure.
The causes of a thrust bearing failure can be traced to a single problem or a combination of problems. In general, though, one or more associated problems are usually to blame, including poor crankshaft surface finish, bearing overloading or bearing surface misalignment.
The throw-out bearing, sometimes called a “clutch release bearing”, is a simple yet important component that’s only in use when the clutch pedal is depressed. When you have a bad throw-out bearing, it will affect shifting and can lead to failure of other clutch and transmission components.
Thrust bearings are used to control end play in the crankshaft. If an engine is assembled with too much end play in the crank, or if the thrust bearing fails, the forward movement of the crankshaft in the block can chew up the main bearing caps and block.
Generally speaking, keeping the thrust clearance at 0.004 to 0.005-inch is appropriate but it is best to check the recommended clearance. For example, late model engines prefer a slightly tighter clearance to minimize travel of the crank sensor reluctor wheel.
Crank run out is checked on either end of a crankshaft with a dial indicator in v blocks to determine how much “wobble” there is in the end of the crank to determine the integrity of trueness.
A dial indicator and magnetic stand can be used to check the ‘run out’ of each main journal. Pinto engines have central thrusts and these should be in place (unoiled) when the crankshaft is turned to prevent possible damage to the crankshaft thrust surfaces through block contact.
The amount of deflection of a crankshaft may be determined by the use of a straight gauge which is simple to apply. The straight gauge is merely a dial reading inside micrometer used to measure the variation in the distance between adjacent crank webs when the engine shaft is rotated by barring the engine over.
Upon initial inspection of the crankshaft, with the use of the micrometer, the machinist will determine what bearings need grinding. Indicators that a journal needs grinding include if the surface has wear and make it rough to the touch.