MG4 luxury HUMS loud when cold at 35mph+

[sava1e]

In the Netherlands it's now freezing two mornings in a row. The first 5 to 10 minutes the car makes a very loud humming noise when driving 35mph+. The tone and volume differs when increasing speed. When the car is heated after a longer drive / in the afternoon the humming noise totally disappears.
Anyone else having this problem / knows what this can be?

a recording here: (humming sounds starts from 0.07)

 

[Tuareg]

Sounds like an aerodynamic issue

 

[sava1e]

Sounds like an aerodynamic issue

Yeah it was my first though too, but why would it disappear when the car/air is heating up?

 

[Tuareg]

Yeah it was my first though too, but why would it disappear when the car/air is heating up?

Some form of expansion of material causing the aerodynamic to change?

 

[NLMGSAN]

F1 flexy wings!
Seriously, have a look underneath the car and check for the bulge.

 

[Ian Key]

Could it be that the Active Grill System is shut when the car is cold and it's the air vibrating the shutters. When the weather/car's warmed up the shutters are open allowing the air to flow freely.

Might be worth checking there isn't anything stopping one or more of the shutters closing fully.

 

[sava1e]

@NLMGSAN
@Ian Key

The bottom looks ok to me?
The shutters were closed normally when I checkled the car. Strangely enough they opened as soon as I pressed the brake pedal. After a minute or two the radiator? was full of ice because it was freezing. Not sure if it's related / can cause that strange sound?
I also did a drive by: outside the car the humming noise is not audible.
I will also let my tires checked, but I don't get why the noise would disappears when it gets warmer.

 

[siteguru]

Regarding the rear undertray ... take a photo from in front of the rear wheels looking backwards. It's the leading edge of the rear undertray that's usually the issue.

 

[OriginalBigAl]

We have an air to air A/C heat pump for the house , when its very cold and humid the air rushing through the outside unit causes the " radiator " section to ice up, it then starts running badly and makes a humming straining noise with the compressor. We have to switch it off and let it defrost then its fine.
I'm suspecting its the same for the unit in the car?

 

[NLMGSAN]

Regarding the rear undertray ... take a photo from in front of the rear wheels looking backwards. It's the leading edge of the rear undertray that's usually the issue.

True. But I can see the bulge in this picture (left side).

 

[sava1e]

True. But I can see the bulge in this picture (left side).

Ok will make another one tomorrow!
Ice on the radiator seems to be related... If there is no ice, there is no strange hum and visa versa.
I don't get why the shutters open when it's -2 outside.

 

[NLMGSAN]

Ok will make another one tomorrow!
Ice on the radiator seems to be related... If there is no ice, there is no strange hum and visa versa.
I don't get why the shutters open when it's -2 outside.

To be honoust, it was -5 this morning and I did not have a humming radiator. But I have no clue whether the shutters were open or not.

 

[sava1e]

To be honoust, it was -5 this morning and I did not have a humming radiator. But I have no clue whether the shutters were open or not.

Would be nice if you can have a look when it freezes. Mine open as soon as I press the brakes. When I lock the doors (and the car shuts off) they close again

 

[NLMGSAN]

Would be nice if you can have a look when it freezes. Mine open as soon as I press the brakes. When I lock the doors (and the car shuts off) they close again

I will.

 

[NLMGSAN]

It opens. It was only 0 degrees and no ice in sight.