Dear Horatio,

Hope you're well. When joining a new pipe (or muffler) to an old pipe - the outer surface of which has rusted and is no longer smooth - a coating of muffler cement (gray, toothpaste-like material) will create a good seal. Apply the muffler cement to the front edge of the inner surface of the pipe, into which a component is to be inserted. The entering pipe will spread the cement.

Muffler clamps - being made of ordinary steel - rust promptly. Even if stainless nuts (or a stainless bolt and nut) are used and have been loosened or removed, the clamp cannot usually be loosened. If the clamp is "U" shaped, with a bar at the bottom, the clamp usually is corrosion welded to the pipe (or muffler). If the clamp is circular, it is hard to spread the clamp. In either case, the clamps can be cut by use of hand-held rotary tool (e.g., Dremel) with an abrasive disc. Even then, the pipes may not separate.

On a cat-back replacement, I use an abrasive diskc to make two length-wise (longitudinal) cuts in the outer pipe (the pipe that slides over the outfall pipe from the catalytic converter). The cuts in the outer pipe should not touch the inner pipe (that exits the cat converter). These cuts go about 3" towards the rear of the car. When both cuts have been made, use a flat-blade screw-driver to pry up on the metal between the two cuts. Levering gently, raise the section of metal between the two cuts, for the cuts' entire 3" length.

Then, take an ordinary hammer and tap the outer pipe (which is going to be replaced). Do NOT hammer on teh catalytic converter pipe as that can damage the ceramic honeycomb and so ruin the catalytic converter.

Tapping on the cut outer pipe usually causes the outer pipe to come free of the cat converter's outflow pipe. You can then remove the rest of exhaust system. I usually use a reciprocating saw to cut the failed units into sections.

Hope this helps.

Yours faithfully,

Spook