A leak-down test measures the percentage of pressure loss in a cylinder over a specific time. Low pressure loss indicates a well-sealed combustion chamber, while high loss suggests problems like worn piston rings, valves, or head gasket leaks. For instance, a reading of 5% or less generally indicates a healthy engine, whereas 10% or higher suggests further investigation is necessary. Specific acceptable ranges can vary slightly based on engine type, age, and application.
This diagnostic procedure is crucial for assessing engine health and performance. Identifying leaks early prevents costly repairs and maintains optimal power output. Historically, mechanics relied on more rudimentary compression testing, but leak-down tests provide more precise data, pinpointing the source of compression loss. This advanced diagnostic capability has become invaluable in modern engine maintenance and performance tuning.
