Leak Down Tester

The Longacre Leak Down Tester (SKU LON52-73010) is an essential diagnostic tool for engine builders, performance mechanics, and serious automotive enthusiasts who need to assess cylinder seal integrity without complete engine teardown. This precision instrument detects compression leakage through worn rings, valve seats, head gaskets, and piston damage—critical information for tuning decisions, rebuild validation, and performance troubleshooting.

The leak down test operates by introducing regulated shop air into each cylinder at top dead center, then measuring the percentage of air that escapes past sealing surfaces. Unlike a compression gauge that only shows overall pressure, this tester isolates leakage to specific failure modes: escaping exhaust indicates worn rings or piston damage, leakage into the cooling system signals head gasket failure, and air exiting the intake manifold points to faulty intake valves. The Longacre design delivers precise, repeatable measurements across all four-cycle engine types.

Its compact 8.4 x 4.6 x 10.3 inch footprint and 2.5 lb weight make it equally at home in a race shop, dyno facility, or mobile service setup, while the robust gauge fittings withstand the rigors of professional use. With a pressure requirement of 90–100 PSI shop air, this tester is indispensable for anyone committed to understanding their engine's true condition.