The aim is to analyze the surface of the product (posterior bearing housing) with using the fluorescent method and to demonstrate the effectiveness of the sequence application like the fluorescent method and instruments of the quality management to analyze the incompatible of the product. In the production enterprise, during the fluorescent penetration test, the incompatibility was identified on the product (posterior bearing housing), i.e. the porosity cluster. The effective of the used the sequence containing the fluorescent method, the Ishikawa diagram and the 5Why method in order to identify incompatibility, and next the source cause was demonstrated. The analyze, the sequence of the methods and the proposed improvement actions can be used in other companies to analyze quality problems.