Final answer:
Crankshaft noise is often more noticeable when the engine is cold due to insufficient lubrication and the components not yet reaching their operating clearances. The noise may also be prominent at low idle if there are issues with the engine's rotating assembly or bearing clearances.
Step-by-step explanation:
When asking about when crankshaft noise is more noticeable, it is generally observed that the noise can be more prominent under certain conditions. However, to provide a specific answer, additional diagnostic information would usually be needed as crankshaft noises can vary depending on different factors. Generally, abnormal noises from the crankshaft or engine bearings could be more noticeable when the engine is cold because the oil has not yet fully circulated or the engine components have not expanded to their operating clearances. Conversely, as the engine warms up (engine is hot), metal expansion and regular oil circulation can dampen the noise.
Engine noise could also be noticeable at low idle if there are issues with the engine's rotating assembly or bearing clearances. However, it is worth mentioning that some noises may persist regardless of temperature or RPM, pointing to potential engine issues that require immediate attention. Therefore, to accurately diagnose such issues, a professional mechanic should examine the vehicle.