What is a key advantage of a leakdown test compared to a compression test?

A leakdown test provides the significant advantage of identifying the specific source of cylinder leakage. During this test, compressed air is introduced into the cylinder at top dead center (TDC) of the compression stroke, allowing technicians to listen for escaping air. This escaping air can indicate various issues such as worn piston rings, valve leaks, or head gasket failures. By identifying where the air is escaping, this test helps in diagnosing the precise location and nature of the problem within the engine.

In contrast, a compression test measures the overall pressure within each cylinder during cranking but does not reveal the specific source of any leaks or problems. It primarily provides a snapshot of the cylinder's health rather than detailed diagnostics, which is why a leakdown test is favored for its ability to provide more diagnostic information.