Remanufacturing within the automotive industry has become an important part of environmental and reusability efforts. A primary function of remanufacturing is the correct identification and classification of defects on the product. This paper will look specifically at cylinder heads within remanufacturing applications to validate and summarize the defects most commonly found on the respective components. A thorough ontology was developed based on a literature review to define, distinguish, and prioritize various defects for remanufacturing. Furthermore, expert opinions within the industry and text-mining were sought to confirm and extend the ontology for defect classification in remanufacturing. The results show that these methods provide sufficient supplemental knowledge to validate critical or underdeveloped areas of the ontology. Expert opinions were extremely valuable in communicating information that is not discussed in scholarly articles and validating information found in scholarly articles.