Hi folks, yesterday when starting my wife’s 2015 C300 I heard a weird single pop sound coming out of under the hood area. I was able to reproduce that sound with repetitive engine start/stops. Although the sound was gone after I drove 15 min to the nearest MB dealership. Any ideas what that might be? Attaching the video for the reference.

 

Sounds nice, the unburnt fuel exiting the engine. Kinda like my car which does it all the time.

 

I noticed my 2015 MB C300 (85,000 miles) just starting to do this too. Two to three popping sounds (same as in video above) like someone sticking their finger in their mouth and pulling it out to make a popping sound. It is coming from the central engine bay under the cover somewhere. It goes away after the car has warmed up a minute or two later. Any ideas?

 

Did you ever find out the cause? Mine is still doing it but seems to run fine afterwards. Three pops on cold start up whether it's warm or cold outside. They seem to be getting louder lately. the sound is exactly the same as in your video.

 

Do you mind posting a video of the sound?

 

Wow... I have never heard this before. If you find a solution, please post it so to help anyone else that has this problem.

 

Just noticed the video is posted in the original post, sounds like something mvoed but also sounds like fluid dropping on to a puddle or the sound of a bubble.

 

Air bubble? Coolant?