Abstract: A leak detection apparatus and method for testing a sealed cavity, but most readily suitable for leakage testing of the cylinder heads of internal combustion engines. The cavity is pressurized either positively or negatively with a probe. The probe is connected to a computer system or control unit containing pressure-sensing devices that measure the inlet and outlet pressures of an orifice of known geometry and dimensions. The cavity leak rate is a function of the orifice geometry and dimensions, the orifice inlet and outlet pressures, the ambient temperature, and the ambient pressure. The computer system determines the leakage rate and documents the test results in both printed and electronic formats. The apparatus can be used on an assembled engine or on individual cylinder heads mounted to a test station.