Joellyr23

I have a 2015 C400 - it was sitting for about 3 years, it was my brothers and he lost his license. Eventually he gave it to me and I got it up and running and i've ran into some issues such as cv joints having to be replaced (I got rebuilt ones), and transmission output shaft seal replaced, and the inner and outer seals of the front diff having to be replaced (the mechanic said they found some metal shavings in the oil but no major damage).

After all that I figured that car should be good to go for the summer but recently i started hearing a knocking/clicking/rattling noise when i was idling at with all my music and climate control turned off. Asking around with a few friends i've heard worst case scenario it could be rod knock, thought that doesn't seem to be an issue with the 400's. My car is tuned with a Morendi Stage 1 tune, it had burbles but i had them taken off. It's also worth noting that when i first got the tune i did fall into an issue where the car went into limp mode when I did an aggressive pull and the tuner said my fuel pump couldn't handle the numbers and they had to make the tune a little less aggressive.

I wanted to make a post hear to see if anyone has ever heard any similar noises from their car (I am really hoping its not rod knock).

Attaching some video's below... The first 2 are sounds from inside the cabin where you can hear the knocking/clicking/rattling sound. The 3rd video is of the engine bay, don't seem to hear the sound there and the engine doesn't seem to be shaking (i was told to check for shaking in case it was the engine mounts). The 4th is from the same day where it seems like the noise had suddenly gone away (I did hear it come back the next day).

Thanks in advance!

Video's are posted below with g-drive links... the first 2 sounded louder on my phone but on a computer it seems a little quiet so you may need to listen closely!

https://drive.google.com/file/d/19Xf...ew?usp=sharing

https://drive.google.com/file/d/1wzD...ew?usp=sharing

https://drive.google.com/file/d/17Ob...ew?usp=sharing

https://drive.google.com/file/d/1S5M...ew?usp=sharing

irondad

The C400 has the M276.42 V6 engine. The wrist-pin issues were in the M284 I4 engine. Having said that...the extra boost could have exceeded tolerances and bent the rods...which it sort of sounds like.

Yegbenz

this is a common noise for c400 and e400 engines, i bought my e400 a year ago sometimes can hear this on idle in the cabin. Got the car inspected by dealer they said its normal as the fuel injectors are quite noisy. There is another thread on this you can find in the e class forums.