I have a 2015 Elantra, 105k miles, living in Massachusetts.
Its a pop that sounds almost like if you took a couple empty, open two liter bottles or milk jugs and bopped them together. I only hear it when I first start driving. 3-4 times in the first few minutes then nothing after that. I have NOT tried starting the car and letting it idle yet to see if it does it too.
Once I’ve been driving for a bit, there’s no more sound for the most part (Yesterday and today I also heard once whlie I was already driving for a whlie, but just the single time). Sometimes it sounds like it’s coming from the driver side door almost, other times from the front end and then one time today it sounded like under the car, so probably the sound echoing? Sometimes it’s really quiet, sometimes loud.
The car seems to run fine, no drop in acceleration or rpms when it happens. I’m really confused what it could be.