Just noticed it today while at a drive through...
Doesn't seem to change with RPM (but engine sound may drown it out).
Also seems intermittent, but is there more often than not.

It also seems to be coming from the rear 50% of the car as I can't really hear it under the hood, but then again not sure. Is it the exhaust?
Will have to get under the car tomorrow when it is bright out to check again, but what do you guys think?

The metallic sound is what just started happening and I'm more concerned about, but I'm also open to what may be causing the sewing machine sound to (been there since I bought the car).

30 second video: https://streamable.com/ctea4

 

I'm no good at determining defects by sound clips. Valves on mechanical lifter engines like ours are "clicky" so are noticeable compared to other cars. The timing chain starts making noise when the tensioner wears out (which is often). If you've not personally adjusted the valves and replaced the TCT I'd start there. Maybe check the exhaust as well. Pending advice, of course, from someone who knows what they're talking about.

-- Chuck

 

Thanks, that's all good advice. Can the sewing machine sound be caused by a worn tct? The valves were done about 30k miles ago.
As for the metallic rattle sound, I think I've narrowed it down to the catalytic converter, or the exhaust pipe behind it. (does the muffler have any parts that can rattle?)
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Ideally you can get the car on a lift and shake things underneath or listen as the engine is running. Catalytic convertor heatshield can rattle as can the heatshields over the exhaust header and next to the battery. If the TCT has never been replaced it's a prime suspect for this type of engine noise as the OE version is notorious for wearing out early. The experts here have heard these sounds in other posts and will, no doubt, advise. I replaced my TCT with our very own Billman unit 2 or 3 years ago at ~40K miles as preventive maintenance. Too simple to not do it. (10 minutes of which finding the 10mm wrench if 5 minutes.)

-- Chuck

 

The mufflers have baffles yes. Could be that, or cat heat shield. That is the most apparent in vid over the sewing machine sound.

 

You guys were right, it was the cat heat shield.

Couldn't get it to stop rattling even after new 10mm bolts, washers, and nuts... also tried stainless steel clamps but that only helped a little during idle.
Not sure what caused it to start to rattle anyways, none of the bolt holes seemed to be corroded or rusted.

Any downsides on removing the heat shield entirely? If I do, not looking forward to removing those exhaust nuts though, unless I can get the top part of the shield off while everything else is still attached to the car.

Or should I just wrap the cat in header/exhaust wraps so it's not metal to metal contact to mitigate the rattling?

 

I've been running heatshieldless for the past there summers. A chunk of concrete ended up under the car at speed, smashed into the headshield, and broke the mounting tabs on my high flow cat that held the shield in place. OE heatshield. Horrible rattle. Took the shield off intending to reweld the tabs back on the cat but...

This is what the high cat and heatshield looks liked before the concrete chunk ended up under the car. Half the shield removed to show the mounting tabs.



The cat is below the right footwell and there should be insulation on the bottom of the body. I've measured the temperature under the carpet and it's not excessive despite lacking the upper heatshield on the cat itself.

Not sure I'd want to park in a field of dead grass without the heatshields though.

-- Chuck

 

Good you found the noise. Id wrap it if you plan to go without a heat shield. Wrap doesn't last for ever so you ill need to stay on top of it. Good thing is it pretty easy to do and you could double wrap it with the typical amount you get in a spool.

 

Does the car have the original timing chain tensioner? Maybe, could use a new one? Along with exhaust fix?

Good luck!