shang12

I asked this on other post but never got an answer from anyone..

so on cold days when I start the car I hear this clunk sound, its just a one clunk sound and that's it.

I took it in MB said this is normal for a c400 as the AC compressor starts up when you start the car to make that sound..

well it doesn't make that sound when its warm out..has anyone else had this issue on there c400?

I had a 2018 c300 loaner and this didn't make the sound and the MB rep said that c400s do make this sound so I want to check with someone that has a 2015 c400

thanks,

j0hn galt

I have a c400 and live in NH where its been very cold. I have never heard that noise.

shang12

that's what I told them I keep saying that sound its like a "bang" sound soon as you start the car in -5 celcuis and colder..

they said they tested with another c400..which I call BS on..

Igotsoul4u

I'm near NYC. I don't know about any clunks but it definitely idles very roughly around freezing or less. A rumble/bump here and there is a little rougher then others. I don't know what to think of it. I am going to test drive a C43 to see if the same issues are present.

Giants54

I have a C400 purchased new which now has 58,000 miles and I have never heard the sound you describe.

shang12

its more of a "bang" sound than a clunk sound now that I hear it more, I took a video of it and not sure how good the sound quality is when I import it on to this site...but if you pay close attention even seeing the hood rattle a bit when that sound is heard soon as I start the car...