US Patent 7367220 Engine oil leak test method with EGR valve leak offset

A method for pressure testing an engine to detect possible oil seal leaks. The engine is charged with a predetermined pressure while air pressure is also applied to an exhaust gas recirculation (EGR) valve intake port to offset leakage inherent in the EGR valve. Thereafter, a pressure drop in the engine pressure is used to determine whether an oil seal leak may be present. Applying pressurized air to the EGR valve intake port compensates for EGR valve leakage and prevents the EGR valve leakage from masking possible oil seal leaks, thereby making the system more sensitive to such potential oil seal leaks.