2021 Chevy 1500 -problem ! popping sound under hood
 

Hi everyone, really hoping someone can share some knowledge on a problem I have just started to encounter with my truck. I have a 2021 Chevrolet 1500 Ltz z71 with the 5.3 v8 with only 3k miles. Recently upon start up I have been hearing a loud popping sound (almost like metal hitting a heat shield or better reference to as a popcorn sound ) under the hood. It only has been happening after the truck sits parked for a few hours then starts but goes away shortly after driving . Took It to the dealership today and they claimed they could not replicate the problem but if It happens again bring It in. Now I get into It after picking It up and the sound happens again. Any clue on what to do or what may be causing this sound ? I will try and get a video the next time I start It . Anything will help .

I have the same problem and am trying to figure out what it is as well.

Leave it with the dealer and use their loaner until they figure it out,

Update : got a video of the sound today. Dealership is going to take another look at It Monday but they honestly have no clue what It might be coming from and are confused why It only happens when the engine is cold.

Bet it's something to do with rapidly heating exhaust components; I would be pretty adamant that I want a loaner and they need to keep it till they figure it out!

I will be leaving It with them till they figure It out but hopefully they can figure It out since the sound only lasts for about 20 seconds upon start up after It sits for a few hours . The exhaust options really sounds like a possibility .

That sounds like the collapsed lifter concern a lot of the 2019 and newer 5.3L engines are having . GM is even building some Silverado's without the AFM and DFM lifters as of march with RPO code YK9. I've had 2 with that same issue. both being collapsed lifters and bent intake pushrods, with one of them also needing a camshaft. Parts are even starting to get backordered with as many as were seeing come through the dealer

My 2020 RST with only 3600 miles is in the shop for the same problem

My 5.3 RST had a bad lifter, dealership replaced all the left side bank…head gaskets were on back order causing a delay…after two weeks I got truck back. Drove it for one day before engine again was making noise. Returned it and they thought it was a bad water pump. They replaced and noise was still evident. Replaced again, still didn’t correct. Now they claim it was a defective head gasket “per a TSB” which led to the noise in the cooling system…I opened a claim with GM for “buyback”

2021 GMC 1500 Denali 5.3 Engine Clacking
 

Mine is making a clacking sound after sitting 10-15 minutes on a warm restart.
Video with sound.