What is a bearing knock?

A bearing knock, or a rod knock develops when the bearings between the rod and crankshaft wear, leaving a gap, allowing the crankshaft to slap the connecting rod. The knock develops slow for a few miles but once the rod starts to knock then the gap increases because the metal in the rod and the crankshaft get destroyed and deteriorated. As the gap increases the knock gets worse, and as the gap increases the knock and the damage will rapidly get worse. Within a short while the connecting rod will break open and get stuck between the crank and the engine block, possibly cracking the block and destroying the crankshaft. The engine is now inoperable :<

To prevent the rod knock, let your engine warm for a minute or so before driving to ensure the engine oil has been pumped throughout the engine, and get regular oil changes, because a thin film of oil is all that separates these engine parts, and dirty oil will be squeezed between the metal parts, increasing the rate of erosion. .