What leak-down percentage is generally accepted as allowable in most engines?

The generally accepted leak-down percentage for most engines falls within the range of 10-15%. This percentage indicates the maximum amount of air that can escape from the cylinders during a leak-down test, which is a critical diagnostic procedure used to assess the health of an engine’s internal components.

When an engine demonstrates a leak-down rate within this range, it suggests that the engine's piston rings, valves, and cylinder walls are in relatively good condition, meaning that excessive wear or damage is likely not present. Higher leak-down percentages may indicate issues such as worn rings, bad valve seats, or other significant internal problems that could affect engine performance and efficiency.

Understanding these acceptable limits is crucial for technicians, as it helps them gauge the overall condition of the engine and make informed decisions regarding repairs or maintenance. Proper diagnostics ensure that the engine operates effectively, meeting emission standards and running smoothly.