My muffler is making a noise after I turn the car off

Yes, I am certain that it is the muffler because that’s where the noise is coming from when engine is off. But glad you mention clamps, I did check rear muffler clamps and hangers and they seem to be tight and not loose. Also when you say the insides of the catalytic converter can come loose, do you mean like the outer heat shield cover that surrounds the catalytic converter? This is a new converter and it should not be making any noise.

In this video you can see what seems to be making the noise when vehicle is off. All other portions of exhaust is okay. Catalytic converter outer cover is tight and not loose. It’s the muffler that is making the noise.

In this video the hangers seem to tight but the muffler moves back and forth. Is it supposed to have some tension making the muffler have some movement back and forth When I rock it or hangers are probably getting worn?

And for the catalytic converter. It’s new and nothing seems to be loose, cover heat shield is also tight. When I smack on the catalytic converter it makes noise from the back muffler which I said in the first videos with the muffler.

Hi Joe, I wanted to reach out to let you know the status of the noise. The rattling and vibration when the vehicle is in drive, reverse or in park when started doesn’t really seem to be much of a problem anymore, it just seem to disappear. It’s just the low pitch noise, like for example if you were tapping on a can very quietly or hearing a very low pitch coming from a horn that’s what it sounds like. I think maybe it’s the metal cooling down because it’s been welded and the metal hasn’t finally got used much yet or maybe there is rust inside.

Now, I don’t know if it’s true, but when I drive, I can hear my muffler rattle in the rear like it’s loose. But I know it’s not because I checked and retighten the hanger bolts as tight as I can. So could that be maybe the muffler hangers are getting worn? I don’t know if I mention this, but when I first had the muffler replaced back in 2017 it never made any noise. Last year it started after the cat was replaced. Nothing seems out of alignment.I only am hearing that sound as soon as you turn the vehicle off after you drive it. Then after while when it sits the sound will stop.

Hi thanks for getting back to me. The catalytic converter was replaced last year. Could newly installed catalytic converters have bad insides? It's brand new and I am not hearing any noise from the front, it's just the rear. I don't hear the rattling or shaking at idle, or in gears like I used to which I mention in the beginning of this discussion. That seemed to fade. Only thing I hear now is coming from the rear. When I tap the exhaust pipe and the catalytic converter, they seem quiet and the only noise I can hear is coming from the rear of the vehicle. As soon as I tap on the exhaust pipe and catalytic converter, you can hear the muffler from the back, tapping against the bumper.

Now when I drive it, the muffler makes noises in the back, like a noise for example, if it was loose. I looked at all brackets, heat shields and hangers are tight. I did notice that the muffler hangers are starting to dry rot. I also still hear that low pitch noise I told you about that sounds like metal vibrating, that's coming from the muffler too. I listen and hear it coming from inside the muffler as soon as I shut the vehicle off after a couple of seconds it starts doing it, than after a couple of mins the sound stops like if the metal inside the muffler just stopped. I never had the problem before the cat was replaced. The shop told me that the muffler shop who installed the muffler and exhaust pipe before cut into the factory pipe that was weld to the catalytic converter. They had to weld new sections of pipe on to the new cat because half of the pipe was too short to fit the new catalytic converter. I am thinking maybe the exhaust is out of alignment. But I don't know if that could cause odd noises you can't find.