During a functional test, what specific engine parameter, when exceeding a manufacturer-defined threshold, indicates potential bearing failure?

During a functional test, an elevated engine oil temperature, exceeding the manufacturer-defined threshold, is a specific engine parameter that indicates potential bearing failure. Bearing failure leads to increased friction within the engine. This increased friction generates excessive heat, causing the engine oil temperature to rise above its normal operating range. The manufacturer specifies a maximum allowable oil temperature. This threshold accounts for normal engine operation and environmental factors. When the oil temperature consistently exceeds this limit, it signals that the bearings are likely worn or damaged, creating abnormal friction. Further diagnostic tests, such as oil analysis to check for bearing material and physical inspection of the bearings, should be performed to confirm the failure. An example would be if an engine manufacturer specifies a maximum oil temperature of 230°F (110°C) during normal operation, and the engine consistently reaches 250°F (121°C) or higher, it strongly suggests bearing problems. While other factors can cause elevated oil temperatures, such as coolant system issues, a sudden and sustained increase beyond the specified limit is a key indicator of potential bearing failure.