Any idea what this noise this?
Thread Starter
Junior Member
Joined: May 2022
Posts: 27
Likes: 14
From: Los Angeles
'19 C63 Cabriolet
Okay, are you serious right now. I'm pretty sure that it is "facts or information relevant to this generation/spec". What I'm not sure about is the tone of your response 
. I was just trying to help even though your over-modulated video doesn't play it clearly. Do I know the exact configuration of every iteration of the W205... No. But I do own one, and it has the "performance exhaust", and it has the "third valve", and I've read numerous threads on the metallic rattling sound being caused by that third valve.
. I was just trying to help even though your over-modulated video doesn't play it clearly. Do I know the exact configuration of every iteration of the W205... No. But I do own one, and it has the "performance exhaust", and it has the "third valve", and I've read numerous threads on the metallic rattling sound being caused by that third valve.People say wrong stuff on the internet all the time. If enough people regurgitate the wrong info, it appears right. There are still people that think and pass along info that a North American spec FL w205 has an OPF, LOL.
Any way I was legit asking if that was facts because:
1. In my deep research, the people stating this 3rd valve (limited at that) are not providing sources or supporting evidence. Literally just their word.
2. a 3rd valve is mentioned and apparent on other MBZ models, but not on any variation/spec of the w205 c-class I can find.
3. Diagrams for a 2019 c63 cab with performance exhaust do not show a third valve, only two, one on each back box
4. Google AI and ChatGPT (paid version) after several back and forth has confirmed there is no 3rd valve.
So, I promise I'm asking nicely, since you have the car and are very confident, can you point me in the right or a different direction please? Maybe diagrams or links or screenshots or info you have that I don't or can't find? I just want to know if I should rule this in or out for my testing. Thank you.
Last edited by jaydp; Jul 29, 2025 at 03:40 PM.
Member
Joined: Jan 2024
Posts: 201
Likes: 60
From: Colorado
2018 C63S AMG Coupe, 2019 Jaguar F-Pace SVR
I can 100% confirm that my 2018 C63S Coupe with a performance exhaust has a 3rd valve in the center section at the H-Pipe. It's right behind the transmission pan... the wiring actually clips onto some of the under-tray brackets right there.
There is an extensive thread about exhaust rattles (including the 3rd valve in the H-Pipe) here: https://mbworld.org/forums/c63-c63s-...63s-coupe.html
There is an extensive thread about exhaust rattles (including the 3rd valve in the H-Pipe) here: https://mbworld.org/forums/c63-c63s-...63s-coupe.html
Thread Starter
Junior Member
Joined: May 2022
Posts: 27
Likes: 14
From: Los Angeles
'19 C63 Cabriolet
I can 100% confirm that my 2018 C63S Coupe with a performance exhaust has a 3rd valve in the center section at the H-Pipe. It's right behind the transmission pan... the wiring actually clips onto some of the under-tray brackets right there.
There is an extensive thread about exhaust rattles (including the 3rd valve in the H-Pipe) here: https://mbworld.org/forums/c63-c63s-...63s-coupe.html
There is an extensive thread about exhaust rattles (including the 3rd valve in the H-Pipe) here: https://mbworld.org/forums/c63-c63s-...63s-coupe.html
I checked under my car and sure enough the 3rd valve was there. Problem is I can't get to it without lifting the car. I'm suspecting this is the culprit so next time I can get the car lifted, I'll see if I can treat it.
Thank you...although mine is faint, I'm hoping it doesn't progress to how bad some of those other guys have in that thread. Good to know there are solutions.
Will report back if this was the issue when I get to it.
Senior Member
Joined: Oct 2007
Posts: 380
Likes: 97
2000 c230 kompressor special edition, 2012 E550 coupe (sold), 2017 C63 sedan (sold), 2018 C63S Coupe
That is the valve he is referring to. While I'm not an expert by any means, everything i can find (pictures, diagrams, aftermarket replacements) all have this valve for the model update cars as well. It is a known issue as others have pointed out, the spring holding the flap shut gets weak and allows the flap to rattle around. My car (2018) suffered from this issue as well, I replaced the spring in the module and it's been fine for a year now. As others have pointed out, there is a lengthy thread with many shared solutions, the 3 I remember are: weld the flap shut and awe valve simulator, copper grease on the spring/in the module (this one didn't work for me), or replacement spring.
The thread is easy to find if you just search for exhaust rattle or something similar.
