Q: Why is it essential to retain old main and connecting rod bearings during engine overhaul on Acura Legend?
A: During engine overhaul, it is essential to retain old main and connecting rod bearings for examination, as they can provide insights into the engine's condition. Bearing failure can result from inadequate lubrication, dirt or foreign particles, engine overloading, and corrosion, all of which must be addressed before reassembly to prevent recurrence. When inspecting bearings, remove them from their respective locations and arrange them on a clean surface to facilitate matching issues with the crankshaft journal. Foreign particles can enter the engine during assembly, through filters, or from machining operations, and can become embedded in bearing material, leading to damage. To prevent this, thorough cleaning of all parts and regular oil and filter changes are crucial. Lubrication breakdown can occur due to excessive heat, overloading, oil leakage, or blocked passages, which can lead to severe bearing damage. Driving habits, such as full throttle at low speeds or short trips, can also negatively impact bearing life by causing oil starvation and corrosion. Incorrect installation of bearings can further contribute to failure, emphasizing the importance of proper assembly practices. If original bearings are worn or if oil clearances are incorrect, new bearings must be selected carefully, especially if the crankshaft has been reground, in which case under-size bearings are necessary. For main bearings, use those with the same color code as the originals, or refer to the codes stamped on the block and crankshaft for guidance. Similarly, for connecting rod bearings, match the color code or refer to the stamped numbers on the connecting rod caps and crankshaft. Ultimately, oil clearance is the definitive factor in selecting new bearing sizes, and assistance from a dealer may be necessary if there are uncertainties.