Rattle/Grind on cold start

[icetaco]

Hi, long time lurker here. I’m also not that technical so apologies if there’s any odd descriptors.


I have a 2024 Off-Road, non-hybrid. I recently noticed a mechanical grinding noise coming from the bottom of the truck (in the video). It has less than 5k miles, and other than the noise, drives like a dream. No awkward shifts/engine hiccups/codes/etc.

The noise seems to be towards the front, coming from underneath.

Some things I’ve noticed about this grinding noise

• Only happens after a cold start (cold being relative - this video was taken in August in Texas)
• Noise starts at almost exactly 2 minutes after ignition (+/- a few seconds)
  • Never happens immediately on startup
• Goes away once the truck is fully warmed up
• Cycling AC seems to disrupt the grinding, but doesn’t remove it all-together (only goes away when the truck is full warmed up and driven)

Some explorations I did -

• Put the truck on a lift, and checked every accessible heat shield I could find all along the way. They all seemed secure.
• Checked the bolting of the cat shield (you can see in the video)
• Looked for gravel/rocks that could be rattling on top of the shield/comp plates
• Opened the hood and listened - the sound was not coming from the engine, but more from the underside of the truck)

Note: My truck also has the infamous startup AC chirp (cold start, you hear a “chirp-chirp” noise when you start the AC). I mention this because I’ve read elsewhere that this could be related to the AC clutch/pulley assembly. Unsure if the noise in the video could align with a loose belt/pulley that is failing to catch until warmed up.


Would love to hear thoughts/ideas if y’all have ‘em!




Thanks again

Sponsored

 

[Yotota]

I'm 98.6% sure that's a heat shield rattle. Check the downpipe/cat off the bottom of the turbo.

 

[icetaco]

I'm 98.6% sure that's a heat shield rattle. Check the downpipe/cat off the bottom of the turbo.

Thanks, yeah when I tapped the heat shields I could access, it had the same tone/note, but none of them were loose.

Would the location of the downpipe/cat be accessed from underneath the truck, and underneath the silver cat shield in the video?

 

[Yotota]

Thanks, yeah when I tapped the heat shields I could access, it had the same tone/note, but none of them were loose.

Would the location of the downpipe/cat be accessed from underneath the truck, and underneath the silver cat shield in the video?

I think you can reach up from underneath, and you can also see some it from the engine bay.

It might also be an issue where the rattle doesn't exist when cold, but does once the exhaust warms up and parts expand from heat. Which will suck to poke around with your hand because the downpipe and cat get HOT AF.

Honestly, I'd let the dealership fix it.

 

[icetaco]

I think you can reach up from underneath, and you can also see some it from the engine bay.

It might also be an issue where the rattle doesn't exist when cold, but does once the exhaust warms up and parts expand from heat. Which will suck to poke around with your hand because the downpipe and cat get HOT AF.

Honestly, I'd let the dealership fix it.

Awesome, appreciate the take on this! Will follow up here when I see the dealer next with the outcome for posterity. Thanks!

Sponsored