Is there a remote control airplane under my hood?!?!

I have a 2008 Kia Rondo. Recently we took a trip from Illinois to North Carolina. Halfway there, we started to hear a humming/buzzing sound (similar to that of a remote control airplane). It was the loudest when we would stop at a stop light/sign, but would stop when the car was put into park. The noise grew louder and louder as the drive went on. The noise was coming from the front region of the car, but couldn’t decipher exactly where. We were able to hear it from the inside of the car as well as the outside. The noise stopped once we reached our destination, but then started back up again on the way back home. Once home, it stopped again and our auto shop couldn’t find anything wrong with it. They didn’t even have an idea of what it could be. Hasn’t done it since we’ve been home. Wondering if driving through the mountains put stress on it. Any thoughts as to what could be making that noise? It’s still under warranty, and if something is wrong i’d like to get it taken care of before that runs out.

‘round these parts, a good ol’ tumble weed trapped near the radiator fan will give a nice buzz.

Inside or under the dash, the heater blower fan will buzz on debris that has fallen down the defroster duct.

The proverbial plastic shopping bag would be the most common road debris to get trapped in vehicles these days.

How many miles are on the car? When and how - if at all - has the transmission fluid been serviced? Has anyone checked the transmission fluid? I would take the description to the dealer. It should get a full scan for error codes.

You should pursue it & keep records of your inquiries at the dealer. This could be a lot of things including very simple and benign things (e.g. a bit of vibrating heat or splash shield). But the fact that putting it in park matters makes me wonder about the transmission pump. Its not the kind of thing that would normally sound like an RC airplane. But a pump cranking out maximum transmission line pressures will make a lot of noise, and if it is doing that, something is wrong.

If a Kia dealer picks up nothing with a scanner then you’re going to have to do what it takes to reproduce it.

The problem could be a weak motor mount, that allows the engine to shift, moving a pulley to make contact with a fender well, etc.

I’ve traced such a noise to the radiator fan.