CRANKSHAFT

1. Common Crankshaft Malfunctions

Another common source of malfunction within the engine is the crankshaft and its related parts. On rare occasions, the crankshaft will actually break into two pieces. This is usually due to metal fatigue, but it may also be the result of poor lubrication that has caused a portion of the shaft to "seize" during operation.

2. Crankshaft Troubleshooting and Remedies

As mentioned before, improper lubrication is the major cause of crankshaft failure. Both the main journals and the crankpins rotate inside friction-type bearings. Without proper lubrication, the crankshaft bearings would last only a few seconds. Improper lubrication can occur with oils that are heavily diluted, contaminated, or of improper viscosity. An insufficient quantity of oil will also cause the bearings to break down long before they should. The result of bearing breakdown is an excessive amount of free play between the bearing and the crankshaft. This can be detected by a "knocking" sound inside the oil pan. If detected early enough, the condition may be remedied merely by replacing the bearings. If not, the crankshaft must be "turned" (ground to eliminate blemishes), and the bearings replaced with a standard undersize bearing. In some cases, the bearing will seize the crankshaft and cause a connecting rod and/or the crankshaft itself to break. There is no method of repair for a broken connecting rod or crankshaft; they must be replaced along with other damaged parts.