I recently had to have the pipe that goes from the muffler to the catalytic converter replaced (it fell off) on my '98 Civic. Now it makes a knocking sound when I first start driving and when I park the car and walk away it still knocks for a few minutes.

I took it back to the mechanic that installed it and he claimed to have fixed it (not sure what he did) but he didn't.

Any ideas before I bring it back to him again of what it could be?

 

like a pinging/knocking sound? my replacment exhaust did that for a long time. I always thought it was the metal they use expanding and contracting due to the heat.

 

maybe its some kind of substance inside of the pipe thats just burning? also new cats tend to do the same.

 

Well, there is a chemical smell sometimes. The mechanic said it was from a label/sticker..the glue heating up. Maybe that's part of the knocking sound? So, it;s nothing to be concerned about? It's a bit embarrasing when you park the car and start walking away..the car's still knocking!

 

yea that might be what it is. just wait a week or so and see how the knocking and smell are.

 

he is right about the metal expanding and shrinking...new exhaust pipes arent heated and cooled like they are when they are actually on the car. i sell cars and when we get new cars in with only like 5 miles in and have to take them from one dealership to another u can hear when they heat up the pipes and when they start cooling down almost like in an old house when it cools off at night in the summer...its not a really loud knock but a noticible knock right??

 

Is it a knocking sound or more of a ticking sound?

 

It's like a ticking sound, yes. It was loud at first but now it's not so bad. It seems to be happening less too. I'll just give it some more time and see if it goes away. I was just concerned it was something gone wrong with the installation of the new pipe. You've all help me feel relieved it's probably not.

It wasn't fun having the pipe fall off while driving home in rush hour traffic. Then, waiting 2hrs, 45min. for a tow truck!

 

yeah its the heating and cooling of the new metal...its just getting nice and comfy in its braces and where its at should go away after a while