So some background info, I bought a used 2009 RX350 AWD at 142k and now I've driven it to about 173k in 3 years without any major issues, primarily worn out bushings on OEM parts from 2009. I change my oil myself every 3k miles (Valvoline high mileage extended life) with a new Toyota filter every time. I did get rear ended last year which got fixed at a local body shop so there is some rattling noises from the exhaust system time to time because of that.

Previously it only made noise when I first bought the car on cold start and would go away, but now it's extremely loud, link to album here. I did end up adding a bit more oil after taking the picture since it was a smidge low. It has the metal oil cooler line (checked visually myself), new KYB struts were installed two years ago, the sway bar link bushings do need to be changed, might need new spark plugs- unsure if those were changed, and some other minor things.

No CEL or anything showing up that would indicate what this issue is.

Anyone know what this sound might be and what the fix would be?

 

Also when pressing on the gas to accelerate there's a heavy spooling up sound and questionable power. Sounds like something is having trouble keeping up and turning as the engine accelerates. Also some metal squealing as I drive that gets louder and faster as I speed up.

 

It could possibly be the a/c compressor doing a death rattle. You could take the fan belt off and start the car and see if the noise goes away.

You don't want to run the engine for more than a minute or two as the water pump won't be turning either.

 

Turns out it was the alternator pulley.

 

Thanks fpr posting about this, and, while glad you found the issue, sorry you have to fix this.