Bush is one of machine and automobile parts like brake used in drums and hubs in particular. Such bush parts are used for bearings of heavy-duty, large cars requiring wear resistance and high load carrying capacity. High temperature diffusion bonding has been applied for holding the both materials of the bushing together, which are outer steel materials and inner composite-sintered bushings. Therefore, it is very important evaluate the bonding integrity in manufacturing process. A simulation has been performed in order to evaluate the maximum defect sizes. Also, ultrasonic C-scan tests were performed for finding the defect in the composite-sintered bushings with the size of inherent flaws.