Rattle inside exhaust pipe

[Shel_B]

There is a metallic-sounding rattle inside the Camry's exhaust pipe. The rattle is located behind the area where the pipe runs from the engine and before the flex joint. I hope the description of the location is clear enough.

It sounds like a piece of metal may have broken from somewhere inside the system, but I cannot imagine where. The engine runs well and is in very good condition. All the usual parameters have been checked in the course of regular maintenance. Fuel mileage is good, power is smooth, and everything seems to be performing well.

Any thoughts on what this may be? The catalytic converter is right up by the exhaust manifold and I'm thinking something in the converter broke. At some point, I'll look into it, but since the car seems fine and there are no indications of this causing a problem, I'm in no rush to tear apart the exhaust system, especially considering local labor rates.

 

[Variant_S]

Could it be a heat shield around or near the convertor?

 

[Danno]

The catalytic converter is right up by the exhaust manifold and I'm thinking something in the converter broke.

Given its age, this.

 

[Shel_B]

Could it be a heat shield around or near the convertor?

No. This is definitely inside the exhaust pipe after and below the manifold.

I have been under the car and have heard exactly where the rattle is coming from. ⁷

 

[MichiganMadMan]

I've had a baffle come loose inside a muffler that I SWORE was coming from the RHS exhaust manifold on a V8 van. Took me a while to find the actual cause, a baffle that was banging around 10 feet away. I think the pipework can do "magical" things with where the sound is generated versus where you perceive it to be coming from. So, it's worth contemplating that you are hearing it in a different spot that it's being generated.

I've also had the "collars" rust out on the ends, where the stainless mesh is retained on a flexi-pipe. They'll only "dance" at certain speeds and loads.
Also, to the other comments: It certainly could be a catalytic converter brick taking a vacation. In that case, this is going to get ugly, you'll need a new one. Any chance you can pull a pre or post-catalyst O2 sensor and have a peek to see if it's there? A catalyst brick out of position will bang and rattle itself to death, so you'll have a good "junk trail" to look at.

 

[c502cid]

I've had a baffle come loose inside a muffler that I SWORE was coming from the RHS exhaust manifold on a V8 van. Took me a while to find the actual cause, a baffle that was banging around 10 feet away. I think the pipework can do "magical" things with where the sound is generated versus where you perceive it to be coming from. So, it's worth contemplating that you are hearing it in a different spot that it's being generated.

I've also had the "collars" rust out on the ends, where the stainless mesh is retained on a flexi-pipe. They'll only "dance" at certain speeds and loads.
Also, to the other comments: It certainly could be a catalytic converter brick taking a vacation. In that case, this is going to get ugly, you'll need a new one. Any chance you can pull a pre or post-catalyst O2 sensor and have a peek to see if it's there? A catalyst brick out of position will bang and rattle itself to death, so you'll have a good "junk trail" to look at.

So much this. My next door neighbor had an exhaust noise that he was sure was coming from the back. I listened to it and was sure it was coming from the front. We were both wrong, it was the cat heat shield in the middle.

 

[Shel_B]

I've had a baffle come loose inside a muffler that I SWORE was coming from the RHS exhaust manifold on a V8 van. Took me a while to find the actual cause, a baffle that was banging around 10 feet away. I think the pipework can do "magical" things with where the sound is generated versus where you perceive it to be coming from. So, it's worth contemplating that you are hearing it in a different spot that it's being generated.

I've also had the "collars" rust out on the ends, where the stainless mesh is retained on a flexi-pipe. They'll only "dance" at certain speeds and loads.
Also, to the other comments: It certainly could be a catalytic converter brick taking a vacation. In that case, this is going to get ugly, you'll need a new one. Any chance you can pull a pre or post-catalyst O2 sensor and have a peek to see if it's there? A catalyst brick out of position will bang and rattle itself to death, so you'll have a good "junk trail" to look at.

Something that might be worth mentioning is that I never heard any rattling or clanking noise when driving. Nor do I hear anything like that when the car is idling and I have a window open., and still don't. My tech found the issue while checking the motor mounts, and wewent under the car together so he could show me the issue.

As I said, I've been under the car and investigated the situation. I don't think that I mentioned moving and jiggling the pipe, and could hear this thing moving around inside the pipe. I can feel the vibration as the thing hits the inside wall of the pipe. It's located in the area about a foot or so in front of the flex pipe which is located (approximately) in the area below where the brake and gas pedals are.

The flex pipe was replaced about 2 years ago and is in perfect condition. It's been examined twice when I did the regular undercarriage inspections.

I don't know what a catalytic converter brick is.

It sounds like a good idea to take a peak through the sensor holes. I am unable to do that but I'm sure one of the techs I use could do it.

Thanks for jumping in.

 

[TheLastWord]

QUOTE: ^^

"I don't know what a catalytic converter brick is."

A failed unit. Needs replacement.

 

[Shel_B]

QUOTE: ^^

"I don't know what a catalytic converter brick is."

A failed unit. Needs replacement.

Just for clarification, it's the entire unit that has suffered a failure/damage and has been "bricked" because it no longer works properly?

 

[Trav]

Something that might be worth mentioning is that I never heard any rattling or clanking noise when driving. Nor do I hear anything like that when the car is idling and I have a window open., and still don't. My tech found the issue while checking the motor mounts, and wewent under the car together so he could show me the issue.

As I said, I've been under the car and investigated the situation. I don't think that I mentioned moving and jiggling the pipe, and could hear this thing moving around inside the pipe. I can feel the vibration as the thing hits the inside wall of the pipe. It's located in the area about a foot or so in front of the flex pipe which is located (approximately) in the area below where the brake and gas pedals are.

The flex pipe was replaced about 2 years ago and is in perfect condition. It's been examined twice when I did the regular undercarriage inspections.

I don't know what a catalytic converter brick is.

It sounds like a good idea to take a peak through the sensor holes. I am unable to do that but I'm sure one of the techs I use could do it.

Thanks for jumping in.

In this case it refers to the type of substrate used, in your car it will be a honeycomb brick, there are other types of substrate like metal and old style pellet cats. These are "bricks" of different shapes and sizes. If the honeycomb begins to come apart it will rattle like crazy in the pipe and may eventually plug the muffler if it is totally broken into pieces, this was common on late 90's - early 2000's VW MkIV and some Nissan 2.5 IIRC, the Nissan ruined the engine.

A clogged cat..

A broken cat, sometimes the whole brick is loose in the shell, it will still work but make a racket.

 

[Shel_B]

In this case it refers to the type of substrate used, in your car it will be a honeycomb brick ...

View attachment 198838
A clogged cat..

View attachment 198839
A broken cat, sometimes the whole brick is loose in the shell, it will still work but make a racket.

View attachment 198840

That was a very useful and understandable message. Great post ... thanks!

 

[LeakySeals]

Like @Trav mentioned the Nissan 2.5 is known to suck broken catalyst back into the combustion chamber as it shuts down. if your cat set up is close to the head replace it.