and the noise you hear happens after the boost builds?

It never happened before and now in the shop for 74 days and 13 different parts replaced, odd that if it was “normal” they would put this much time, work and money into it...no?

would love to hear a sound clip of the noise you’re hearing in your car.

i will take a sound clip for you today. I never noticed it with the stock air box, but once i put the intakes on it was immediately heard. Yes i do agree it is odd with all the part changes they have done however, the parts they changed dont seem to make sense to me. To me it is def an air/forced induction type of noise. Do you have the stock airbox?

I appreciate you doing that!!

I do have a stock intake but replaced stock filters with K&N filters back at the beginning of September.

And I agree, some of the things they replaced make absolutely ZERO sense to me. This was the message I received yesterday:

"... technician had a couple of road tests done today, removed wiper arms, inspect ABS/ESP module and the fluid lines round there and etc to see if the noise goes away, but unfortunately the noise is still here."

WIPER ARMS?!?

Like I said in the title, they seem to be clueless. 🙄

You will hear it with K&N filters, but not with the stock paper filters. At least that is my experience. I’ve also had BMS and MST intakes and those make the sound in question extremely audible and obvious. In my opinion, there’s nothing wrong with your car.

I guess what I find the most odd is that of all the places I've posted this, all the work they've done on it at MB and parts replaced, sound clips to MB Canada...no one has said "it's normal when running K&N filters"

I appreciate your thoughts though on it. I'm almost hesitate to ask them to just put in stock filters and test again...could you imagine that really was the issue? 😬

I did mention the sound being discernible with K&N in post #8, just in case you forgot. 😁

no never forgot but again it seems odd and kinda scary that 3 technicians, a service manager and MB Canada would replace so many items Over the past 74 days when you’re saying the sound is completely normal when using a K&N filter.

Sounds like they have been trying hard to resolve the issue for you by changing out all those parts. The staff at MB probably are not used to driving vehicles with k and n filters as most people would be on stock filters, so not surprising they would not recognize a nuance of the after market filter causing the audible change specifically in a FL C43. Honestly hope that’s all it is and that your car is healthy!

yes they definitely have been trying hard to resolve the issue but again I just can’t imagine of all the people working on it or at head office, not one single person would think that this abnormal “grinding” noise is being caused by K&N filters.

I don’t know, but K&N/drop-in filters where discussed in posts #8, #10 and #20 as contributing to the noise, but you’ve only now mentioned that you have K&N filters yesterday in post #28 and it also does seem like you put those filters in at or around the time you noticed the noise. Not sure why you wouldn’t put that on the table earlier. I’m sure the guys at the dealership would have benefitted from that bit of information. It’s almost as though you’re testing them, and in a way testing us too without letting us know all the background information.

Really?? Testing?? Yes this is just some big experiment where I drive base model loaner cars for the past 74 days but continue paying my monthly AMG premium payments...yes my friend you totally busted me.

Oh and on a side note...the techs and service manager already knew about the K&N Filters. You think after replacing 13 different parts (including 1 of the turbos and both diverters) they wouldn't of noticed or looked at the filters?

I’m sorry your car is broken, I hope they resolve it soon.

I appreciate that...and yes I hope so as well.

I have been looking through some old threads of yours trying to find where you talk about this same noise, but I can't seem to find anything. You remember where you mentioned it in the past? I know you sold your car are you weren't really fan since the 1st week of ownership, but I'd love to read some more on this apparent K&N filter issue. I bought some BMC filters...you think these will produce the same "grinding" noise? Are you saying the only way to get rid of this sound is going back to stick air filters?

It’s not K&N specific, in fact it is much better with the drop-in than the open cones from BMS or MST. I did all the filters systems available at the time and then quickly sold the open cones and settled with the K&N because it managed the sound the best. It had the least chugging sound of the lot. We have BMC on one of my friends C43 over here and it’s the same as the K&N. To my ear, it doesn’t happen with pre-facelift cars and I think it’s due to different turbos or different boost levels, and how the new car manages that at lower loads.

I’ve moved back to an Audi and I couldn’t be happier.

Yeah I came from the Audi world and this past 74 days of having my car at the dealership with them not knowing what is causing the noise is making me regret the move somewhat. I still cannot believe this is simply caused by the K&N filter. I think I might buy some stock filters, ask for my car back and test 😬

I know i meant to get some sound clips up but had to work over the weekend. I will try and get them ASAP. But for what its worth the sound i hear is exactly what you posted in the video just louder with BMS intakes. Its def not a grinding noise but more of air/boost flowing through piping that becomes more apparent with different filters or aftermarket intake. To me it sounds like its just modulating boost at certain loads. I am a car enthusiast and had over 20 different various makes and models of cars and in my previous profession was an auto tech. In my opinion this noise is completely normal. That being said its quite odd what MB has been changing on your car. I would not let them change random parts on my car without proper diagnosis. However i dont believe there is anything to diagnose in your car.

i am pretty sure the service dept makes money from warranty claims - therefore as long as they can prove to HQ it was reasonable, they won't hesitate to replace anything !

yes of course they do. I just wouldnt want the tech that thinks wiper arms and flywheel bolts are the cause of the noise taking my car apart lol