C300e strange noise at specific speed

[JORDANKOUL4]

Hello to everybody and happy to meet you!

Unfortunately I have to introduce myself with a problem I have with my C300e.
Some information about it:
2023 model
17.000km
The problem is a high tone sound that comes only around 75-77 km/h and only at that speed. Everything below that or above, it fades away.
- I already tried different tyres but the noise remains.
- Noise doesn’t seem to change when I am on D or N
- Noise is there when I turn left or right
- Noise is there on all modes, electric, sport, hybrid etc.

I am not sure but the only thing I managed to understand is maybe the sound is temperature related because certain days the noise almost disappeared and other days is unbearable.

I added a video where I think you can hear the noise clearly.
I hope for your help.
Thank you all in advance!!

---

C300e.mov

 

[Petrol Pete]

Hello and welcome .

You don't have roof bars fitted do you , or any other sort of external fitting/appendage that could be harmonising at specific speeds ?

Long shot I know.

 

[JORDANKOUL4]

Hello and welcome .

You don't have roof bars fitted do you , or any other sort of external fitting/appendage that could be harmonising at specific speeds ?

Long shot I know.

Thank you for your reply!
No I don’t have roof bars fitted!
Does it seem to you like harmonising sound?
I am trying to think about changes that might have happened from the time I bought it..
And the only thing I had is a slight hit I had on the right front low from a motorcycle which broke a plastic trim on the fender.
Maybe something broke behind it and lets the air get inside the car?

 

[SpikyMikey]

I initially thought it might be a noise generated from something in the hybrid system; it sounds a bit electric motor-ish, but it very well could be a piece of loose trim resonating in the airflow. Would be worth checking around that area where the damage was for anything loose or out of place.
Whatever, it's a really annoying noise! Let us know how you get on

 

[JORDANKOUL4]

I initially thought it might be a noise generated from something in the hybrid system; it sounds a bit electric motor-ish, but it very well could be a piece of loose trim resonating in the airflow. Would be worth checking around that area where the damage was for anything loose or out of place.
Whatever, it's a really annoying noise! Let us know how you get on

It’s really annoying yes and I hit the pedal the last few days to get away fast from that speed..
My first impression was the hybrid system because the sound was like the one that the electric motor does but in a higher tone.
But I went on a local garage and hit the exact speed while the car was up in the air, the noise disappeared and couldn’t locate it.

 

[SpikyMikey]

It’s really annoying yes and I hit the pedal the last few days to get away fast from that speed..
My first impression was the hybrid system because the sound was like the one that the electric motor does but in a higher tone.
But I went on a local garage and hit the exact speed while the car was up in the air, the noise disappeared and couldn’t locate it.

That does seem to suggest something moving in the airflow then...which would be better for your credit card than something wrong with the hybrid system

 

[JORDANKOUL4]

That does seem to suggest something moving in the airflow then...which would be better for your credit card than something wrong with the hybrid system

It will be better for my credit card for sure
I will try to check everything out of position then.
Because at first I thought it was too loud to be produced by airflow

 

[SpikyMikey]

Because at first I thought it was too loud to be produced by airflow

Have you ever heard a Clarinet?

 

[JORDANKOUL4]

Have you ever heard a Clarinet?

clarinet yes but not inside a car

 

[Petrol Pete]

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[JORDANKOUL4]

I put tapes almost everywhere but I couldn’t change anything, noise keeps coming.
Also, I checked again the history of the car ( I bought it with 10.000km on) and I saw that the dealer had replaced the PTC heater.
Is it possible the noise coming from there ?

 

[SpikyMikey]

I put tapes almost everywhere but I couldn’t change anything, noise keeps coming.
Also, I checked again the history of the car ( I bought it with 10.000km on) and I saw that the dealer had replaced the PTC heater.
Is it possible the noise coming from there ?

I wouldn't have thought so, PTC heaters are just resistive elements.

 

[JORDANKOUL4]

I wouldn't have thought so, PTC heaters are just resistive elements.

Ok so that’s not it! A local garage suggested to check the fuel filter.. is it possible for the fuel pump to produce such a noise?
Also, the outside temperature reached 17-18 C today and the noise was almost unnoticeable..
It’s going to drive me crazy