Before beginning work on an exhaust system, make sure it is cool to the touch. Some technicians disconnect the battery’s negative cable before starting to work to avoid short-circuiting the electrical system. Soak all rusted bolts, nuts, and other removable parts with a good penetrating oil. Finally, check the system for critical clearance points so they can be maintained when new components are installed. Most exhaust work involves the replacement of parts. When replacing exhaust parts, make sure the new parts are exact replacements for the original parts. Doing this will ensure proper fit and alignment as well as ensure acceptable noise levels. Exhaust system component replacement might require the use of special tools (Figure 32–34) and welding equipment.