What should be checked when there is a concern about the oil clearance of a crankshaft and main bearing?

When evaluating the oil clearance of a crankshaft and main bearings, the measurement of oil clearance is critical for ensuring proper engine operation. One effective method for measuring this clearance is using Plastigauge, a small strip of gauge material that provides a precise reading of the clearance between the two components when compressed.

By placing the Plastigauge between the crankshaft journal and the main bearing, the technician can tighten the bearing cap, then remove it to see how much the Plastigauge has flattened. The flattened width corresponds to a specific measurement that indicates if the oil clearance falls within the manufacture's specifications. If the clearance is too tight or too loose, it can lead to inadequate oil circulation or excessive wear, potentially causing engine failure.

While other factors like the condition of the rod bearings, cylinder pressure, and engine oil type are vital for overall engine health, they do not directly assess the oil clearance of the crankshaft and main bearing, making Plastigauge measurement the most relevant and focused method for resolving concerns regarding oil clearance.