Hello guys,

I have a 2012 w204 c63 with 49k miles .
Stock exhaust, stock car.

I have this annoying rattling/buzzing sound like a diesel engine coming from the right side (RHD) every-time I accelerate on low speed in higher gear (normal city drive) from 2000rpm till 4000rpm

Video:

https://youtube.com/shorts/i2qSP8rairk?si=ig3Ws-c1qxrdtaRY

Everytime i let go of the accelerator paddle and apply some gas this buzzing/ rattling sound comes, can be heard in the video.

I have taken the car to have the exhaust checked and found zero leaks, changed the header gasket just in case , didn’t fix it.
Checked the cats they were in good condition , even swiped then with my friends car but the sound is still there.

Anyone suggest what could be causing this sound inside the car, i can hear it very low when the car is in park and i give gas, but when driving it more noticeable.

 

If stepping on or off the gas is related to the problem, it could be a transmission mount going bad…

 

Were the heat shields underneath the car checked?

Buzzing (vibration) under loads, especially lighter ones, can be caused by something loose / unsecured.

 

Before i had bigger things checked we had checked all heat shields , exhaust system , cats even changed the right side header gasket nothing changed, the sound remains i even had my cams and lifters checked that maybe the cam or cam hear is lose but that were all good.

so after checking leakages ect i dont know what could be causing this buzzing sound on accelerating from
the right side of the cabin 😢 its really annoying to the
its really always there evey time I release and press the gas paddle on around 2500rpms too 4000rpms and gear when the car is on load only.

 

This sound is only present when driving and on load, i can maybe hear or replicate it on park / neutral gear but its not as bad as when in gear and driving.
But ill have all the mounts checked out and report back asap.

 

Update: took the intake off checked for leaks disnt find any, check all exhaust shields all are okay and non are vibrating, changed the engine mounts as one of them was bad but that still didn't solve the annoying buzzing sound on light RPM acceleration mostly btw 2500 rpms and 4000rpms

sounds like a exhaust leakage but there isn’t any leakage checked 3 times and 3 different shops.

its always there every time I accelerate on any gear when i let go and the apply accelerator paddle again.

video:


https://youtube.com/shorts/i2qSP8rairk?si=bvtXBJ6aQvLfWjrb

anyone could please suggest any thing to check it would be very helpful.

 

I get the same exact thing on my 2014.
I get it at 1400-1800rpm and then its smooth above 2k. It doesn't do it just reving in N either. It has to be under light load. Sounds like an exhaust leak or a heatshield rattling. Some aftermarket headers make noise like that through the metal but Im pretty sure mine are stock.
It makes me think something in the engine bay or between the firewall is just resonating/vibrating on something somewhere between those rpms because the car drives fine otherwise.

 

you sure its not from interior as in this video ->

 

i have the same or a similar problem. I get a rattle between 1400 -1900, smooth above 2k. It happens when the engine is under load when in higher gears mostly. Sounds like an exhuast or heat shield rattle but i've checked the exhuast and heat shields repeatedly and found nothing. I have ARH headers and after market engine mounts and i'm wondering if it's that. The ARH headers are also a really tight fit and it looks like they touch my motor mounts so my one guess is maybe that's the cause but i'm not sure. It also sounds like the noise is coming from the rear if the car but i know noises can travel and be deceiving. Wish i could find it as it annoys me sometimes.