Check for Complete Trademark Markings. Genuine products feature high-quality outer packaging with clear lettering and vivid color printing on the boxes. The packaging boxes or bags should display the product name, specifications/model number, quantity, registered trademark, manufacturer's name and address, and contact information; some manufacturers even stamp their own specific markings directly onto the parts themselves. Certain critical components-such as alternators, distributors, and fuel injection pumps-are also accompanied by instruction manuals, quality certificates, and inspector's stamps to guide users on proper usage and maintenance. When making a purchase, examine these details carefully to avoid acquiring counterfeit or substandard products.
Check for Geometric Distortion. Some parts are prone to deformation due to improper manufacturing, transportation, or storage. To inspect shaft-like components, roll them across a flat glass plate; observe whether any light passes through the contact point between the part and the glass to determine if the shaft is bent. When purchasing clutch driven plates (steel plates) or friction discs, hold the plate or disc up to eye level to check for warping. For oil seals-specifically those with internal metal frames-the end face should be perfectly circular and sit flush against a flat glass surface without any distortion; for frameless oil seals, the outer edge should be uniform and true-when squeezed by hand to induce deformation, the seal should immediately spring back to its original shape upon release. When purchasing various gaskets and seals, pay close attention to verifying their geometric dimensions and overall shape.
Check the Mating Surfaces for Flatness. During handling and storage, parts and components are often subjected to vibrations or physical impacts, which can result in burrs, indentations, damage, or cracks on their mating surfaces; such defects can compromise the functionality of the part. Always inspect these surfaces carefully before making a purchase.
Check for Surface Corrosion. High-quality auto parts possess both precise dimensional accuracy and a bright, polished surface finish. The more critical the component, the higher the required precision and the more rigorous the anti-rust and anti-corrosion packaging measures typically are. Inspect parts carefully during purchase; if you discover rust spots, mold spots, or if rubber components show signs of cracking or loss of elasticity-or if a journal surface exhibits obvious machining marks-the item should be rejected and exchanged.
Check the Protective Surface Coating. Most auto parts are coated with a protective layer before leaving the factory. Ensure that this protective coating remains intact and undamaged. Components such as piston pins and bearing shells should be protected with paraffin wax; piston rings and cylinder liners should have their surfaces coated with rust-preventive oil and wrapped in packaging paper; and parts like valves and pistons should be immersed in rust-preventive oil before being sealed in plastic bags. When purchasing, if you discover that a protective seal is broken, the packaging paper is missing, or the rust-preventive oil or paraffin has leaked away, the item should be returned or exchanged.
Check for looseness in bonded components. For spare parts composed of two or more individual pieces-which are joined via press-fitting, bonding, or welding-there must be absolutely no looseness between the parts. Examples include the oil pump plunger and its adjustment arm (joined by press-fitting); the clutch driven plate and steel plates (joined by riveting); the friction plates and steel plates (joined by riveting or bonding); the paper filter element frame and filter paper (joined by bonding); and the wire terminals on electrical components (joined by welding). If any looseness is detected during purchase, the item should be exchanged.
Check for smooth rotation in moving parts. When purchasing assemblies containing rotating components-such as oil pumps-manually rotate the pump shaft; it should turn smoothly without any sticking or binding. When purchasing rolling bearings, support the inner ring with one hand and spin the outer ring with the other; the outer ring should rotate quickly and freely, then gradually come to a stop. If a rotating component does not turn smoothly, it indicates internal corrosion or deformation, and the item should not be purchased.
VIII. Check for missing parts in assemblies. Legitimate assemblies must be complete and intact to ensure smooth installation and proper operation. If even a single small part is missing from an assembly, it may render the entire assembly inoperable or even result in it being scrapped.
