gabemcclintock

I have loved my Mercedes (owned a 2016 CLA45, 2018 C43 and now a 2019 C43.

Mysterious Grinding noise:

You Tube

Timeline since November 10th with local MB dealership here in Calgary trying to fix it:

- Replaced drive shaft centre bearing and rubber mount
- Replaced the left turbo charger assembly, diverter and right side diverter
- Replaced the front axle propeller shaft assembly
- Replace intake and exhaust cam solenoids
- Replaced transmission assembly without the torque converter
- Replaced transmission torque converter
- Replaced flywheel bolts
- Replaced front propeller shaft bolts

Noise is still present and is getting worse which has been acknowledged and confirmed by technician on January 5th 2021.

Not sure what to think anymore and they still have no idea what is causing the noise.

mau108

Is the noise only there when you lift off on the throttle or at a certain speed?

ABC43

Which dealership do u go to? Country Hills?

gabemcclintock

No just when the boost recedes as the car shifts. Doesn't seem to happen past 3rd gear...I really notice it when accelerating slowly, not so much on WOT.

gabemcclintock

LoneStar

user33

A thought ... my C63 S had some strange buzzing-like noises under certain types of acceleration in lower gears. I suspected vibrating under panels and/or heat shields. After talking to the (excellent) shop foreman at my dealership, he indicated that that type of problem does occur.

Since it was faster/easier for me to look/adjust/test, the next time I did an oil change, I carefully examined the under panels and heat shields, tapping them at various points to see whether they'd vibrate against adjacent pieces. Wherever I found suspect places -- primarily multiple heat shield locations -- I adjusted the clearance and/or made sure the fastener was properly holding. One of the "center expanding plastic insert thingie fasteners" was loose so I replaced it with a larger one. For my case, that session completely eliminated the buzzing-like noise.

gabemcclintock

Would that noice be directly related to the turbos?

TModelle

I got that sound all the time on my 2019.
More obvious when you switch the stock air box to an aftermarket intake. If I used a K&N drop in, it was also audible, but just barely.

gabemcclintock

Are you referring to the blow off?

The "grinding" noise which starts around the 4 second mark and happens 3 times consecutively has never happened before. I've had a 2016 CLA45 and a 2018 C43 and never had this noise before. And this noise wasn't present until about 3-4 month ago.

stockbmw

Just a thought when tmodels car is louder with the kn filter, there is vortex generator just below the air filter, inside the piping to the turbo, maybe it broke off and is hitting the turbo fan

TModelle

Yes, that exact sound. I could replicate it if I had the right load and right pedal pressure.

Do you have an aftermarket air intake installed. It makes it very much more obvious.

gabemcclintock

It’s not the blow off sound you hear...it’s the “grinding” noise that is the thing in question. And no I don’t have an after market intake installed.

TModelle

Yup, I tend to describe it as groaning and it is repetitive when it occurs. Bad toilet plumbing as I would say on other threads in this forum.

gabemcclintock

I would hope the MB techs wouldn’t replace 13 different parts over 2 months on the car due to normal blow off 😬

superswiss

I could be wrong, but this sounds like turbo flutter, which is caused by a compressor surge. It's like a choo-choo sound, which is also the slang term for it. Should only occur in an unvented turbocharged engine, or if the diverter valve is not releasing the pressure, but I see they replaced your diverter valves already. Maybe the replacements aren't working correctly, either.

gabemcclintock

Could be why they replaced both diverter valves thinking the same thing. But what would the odds be that even the replacements were defective? I’d imagine convincing them to try and replace them again would be next to impossible.

superswiss

You'd be surprised how often replacement parts arrive defective. They are often carelessly stored in warehouses w/o much packaging or any packaging at all and the shippers are not particularly careful, either. I went through three transmission oil pans on my previous car for example, because the first two were bent when they arrived and leaked. They didn't even install the second one, because they measured it before installing. Third one was finally good. This was with Audi at the time, but it's the same everywhere. They should test it to make sure the valves are actually doing their job.

gabemcclintock

yeah I have no doubt this happens but trying to request MB techs to order and install parts they have already ordered and replaced seems like it would be next to I possible...especially since they seem to have no idea in what is causing the noise

superswiss

Well, by now they should have brought in a field engineer, but I understand that's a bit difficult with the current COVID situation. As far as I know MB and others are currently not sending out field engineers. Not sure how your dealership is equipped, but I thought MB corporate was putting video conferencing in place so they can help diagnose and fix issues virtually. In my case above, Audi immediately flew out a field engineer when I brought the car back for the second time and he stayed until the issue was fixed. You should ask for the issue to be escalated. There's a process for that, but I can't remember at the moment what it's called, but if invoked AMG engineers get involved.

TModelle

It’s likely a 2019 model thing. Among my C43 group locally, the 2019 models exhibit that behaviour and that’s why none of them run BMS or MST intakes as it makes the awful sound louder. They sound okay on pre-facelift models though.

If you remove the baffles inside or use a drop-in panel filter, it also makes it louder.

gabemcclintock

I don't think what you're hearing or referring to is the noise in question.

I've had a 2018 C43 and now this 2019 and the noise was non-existent on the 2018. It's not the blow off sound I'm referring to. It's the choo-choo-choo sound at around the 4 second mark.

TModelle

Yup, that’s the sound. “Cuh, cuh, cuh, cuh”. Exactly that. Happens all the time. I’ve made many posts in the past saying that my car sounds like bad plumbing. One of the reasons I didn’t like the 2019 C43. Doesn’t seem to happen on pre-facelift cars.

gabemcclintock

Didn't happen on my 2019 either till about 5 months ago.

gabemcclintock

Do you happen to have sound clips of that noise happening on your car you could share?

David Hudak

i have a 2020 c43 with BMS intakes. I have the exact same sound that you have in your video that starts around 4 seconds. It only happens when I accelerate very lightly and am only partially under load. I thought it was normal and to me it sounds like its the diverter valves opening and closing because you are basically in between building boost(load) and no load releasing pressure.