Cat replaced now heat shield rattles?

Could be a heat shield not secured properly.
Did you get a cat shield?

 

Is it something that would record well?

 

Seems like too much coincidence

 

Nah you're in conn. I used to live over in Windsor locks right next to Western Massachusetts near the prison the federal. I can't remember what the laws were for emissions back in the 85. I would have hoped by now they might have gotten a little more lax so that is maybe as long as the catalytic converter is in place it doesn't matter whose it is but I don't know that I know a few states have gotten to the point where they're just not fooling with this.

 

The metal that the shielding is made of can easily be bent... Sounds like all your fasteners are there because the rattling is infrequent. Just got bend stuff to get it to quiet down. Meanwhile, cat shields only cost like $70 and can be installed in a 1/2 hour. You might as well get one if you have to fix the shielding noise under their any ways.

 

It sounds like the heat shield to me.

The cat heat shield is just thin pre-shaped aluminum. It's around the thickness of a disposable aluminum cooking pan for a Turkey.
If your previous cat was stolen, then any dent/etc in the heat shield, can make the shield be noisy at times.
It's not dirt cheap. So, they rarely replace it, unless it's very damaged. I think the exhaust needs to be dropped to replace the shield. So, that adds another ~1 hour, or $100-$200 to the replacement cost. There are often nuts/etc that get rusty, and need to be heated off, then replaced, and so on. So, the total time may be over an hour. Add in the cost of the parts, and it's now a $200 to $400 job.


You can see, and get an idea how the heat shield attaches to the car, in the following video - start around 11:10mins.

Code:

Start at ~11:10

https://youtu.be/fVXOOpw2PJU?t=679
This is One Toyota Corolla Model You Might Want to Avoid Unless The Engine's Been Fixed
The Car Care Nut

In the pictures below, you can get an idea how the cat heat shield is attached on a Gen4 Prius Prime:








Good Luck!

 

If you replaced the catalytic converter after a theft, I have found that its pretty easy to damage the heat shield that is just behind the cat ( and just forward of the resonator). That part may have been cut by the reciprocating saw used to quickly cut out the exhaust. It probably should have been pretty obvious during install of the replacement.

I have had issues with rust through on those thin shields, especially the one over the muffler. In most cases (assuming rust belt locations) the fasteners may be impossible to remove, but if they can, a good stainless steel fender washer might do the trick to repair rather than replace that part. They seem to rust under the fastener and just fall.

Worry about theft?

Since you mentioned worrying about theft, if you got an OEM catalytic converter from Toyota, you should be concerned. If you got an aftermarket converter, the thief should be able to see that pretty clearly and move on. Nobody wants to take a part worth $100 or less when they can get 10x that amount for the Toyota made part. FYI... I would not assume that a dealer used an OEM part. Reach out to the mechanic or check the receipt to see what was installed. A catalytic converter part under 1K is not the original Toyota OEM part.

 

Basically an oversized washer, larger outside diameter than usual for hole size. Good for spanning torn out holes.

 

FWIW, I got newly replaced OEM catalytic converter from the prior owner whose insurance company paid for it just before I bought it.

Subsequently I bought a MillerCat stainless steel Complete shield system and had my Toyota dealer install it even though I have zero deductible comprehensive insurance but don’t want the hassle of replacing it again nor did I want my policy dinged.

I noticed that after the MillerCat shield was installed the exhaust system was quieter. I didn’t really notice noise before or was not bothered by it but noticed the lack of it afterwards.

No guarantees the shield will prevent theft but it’s the best I can do and the noise reduction was a bonus.

 

You’d think they’d hear it, if they bothered to test drive.