[Mepsipax1]

Hi all,

I've recently purchased a 330d and got it home via a 100 odd mile drive with everything running smoothly and no unnerving noises. A few days after driving it around I've noticed that at higher speeds a buzzing sound starts to build up, I can drive it around up to about 50-60mph with no sounds but as soon as I start going above that there's a constant buzz, once it starts I can hear it at speeds as low as 25mph.

The sound itself is a constant pitch no matter what speed, however its volume is speed dependant, similar to how the audio systems "speed dependant volume" works. I've tested the system but no audio settings change it. It doesn't change when I steer left or right, isn't RPM dependant as even coasting doesn't affect it, acceleration and braking doesn't affect it other than what would normally change with speed, and it appears to be coming from the front of the car. There are very few road surfaces (I think very new flat surfaces) where the sound does actually disappear.

The noise isn't a rumble, screech, whistle or anything like that, it's just a buzzing sound. I've had wheels balanced, rotated and tracking done, I've taken off and refitted trim, pressed trim pieces whilst driving, tried different combinations of electronics (lights on/off, fogs on/off, radio on, aux, fan settings etc) however I can't seem to figure out what's actually causing it and it's driving me mad

I honestly don't believe it's a bearing and if it turns out to be that I will run myself over with the car, I've looked up videos on it and my noise is lacking the wumpwumpwump or any other recurring noise, it's literally just zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz, or ZZZZZZZZZZZZZZZZZZ if I speed up lol. Currently believe it to be an electrical issue, possibly to do with something like steering tightening at higher speeds or something of the sort.

Sorry for long first post but if anyone has any ideas or has experienced this before, please let me know as I am out of ideas. My brain currently >

[Watsey]

Have you checked the engine trim cover ? They can vibrate and cause a loud buzzing by the edges knocking against various engine components such as the inlet manifold.

I've got several felt pads inserted around nine and eventually managed to make it quiet. Definitely a piece of poor design.

Apart from that, it could be a long list of things to check. A wheel bearing would be high in my list.

What's the mileage ?

[Mepsipax1]

I've done a little drive and checked various bits, took the engine cover off for a sprint and whilst it did remove some rattling and I definitely will be sorting that soon probably with some felt like you have, the buzz is still there.

I did notice some bits of grille on the front that were broken, stuck some foam pad between the broken bits, also did the same with the front reg plate as this was quite loose at the sides, and removed a random nut from behind the bottom grille, none of this really did much to the buzz however I have a suspicion that something like that could be causing it.

I've asked my mechanic to check out the bearings on Monday, will update with what he says.

Mileage on the car is 124000ish. It's ex-CID so there's not a lot of paperwork on exact work on the car so I don't know if wheel bearings have been done before but it does have full service paperwork and the recalls and such.

[Watsey]

I've just had the rear wheel bearings replaced on my 30d - car has done just shy of 100K miles.

The noise started as a w-w-w linked to wheel rpm and the worsened to a continuous wwwwww at speed as well as a buzzing inside the rear of the car.

The noise only started at speeds above 35mph - completely silent below that.

[Mepsipax1]

If mine is the wheel bearing then it seems to have skipped the w-w-w stage, or its only very slightly worn and that bits not noticeable yet compared to the buzz.

Did your buzzing ever change pitch? mine is a constant tone, louder with speed though

[Animal7]

Originally Posted by Mepsipax1

If mine is the wheel bearing then it seems to have skipped the w-w-w stage, or its only very slightly worn and that bits not noticeable yet compared to the buzz.

Did your buzzing ever change pitch? mine is a constant tone, louder with speed though

Don't suppose you have dimpled/grooved discs on the front? My Brembo discs can be heard when windows are open making a kind of brrrrrrrrr type noise.

[HighlandPete]

A constant tone which increases in intensity, as speed increases, could be involving the structure. There have been issues with badly fitting trim under the cars.

I'd be checking out the engine under tray, wheel arch liners, etc., for proper fit. Including any road debris. Something like a trapped twig or plastic bag can sound like something is mechanically failing.

[Mepsipax1]

Animal7 - All my discs look just about perfectly flat, looks like they're all pretty new (Edit: also I can't seem to pick out the noise over the wind when the windows are slightly or even fully open)

HighlandPete - I can see some leaves and stuff about, there's two at the side of the radiator and then some under the plastic/rubber shielding just below the windscreens plastic bit at the bottom, will try cleaning them out later on today.

Unfortunately I don't have equipment to lift the car to check the trim underneath but I'll ask my mechanic to check those as checking for any structural issues as well when he comes on Monday. In the mean time I might just try slap some foam pads between trim pieces and hope for the best Lol.

[SW6Steve]

There is a thread, with pictures, on here of buzzing from the undertray, but I'm blowed if I can find it now. You may have better luck!
It was just a case of putting on full steering lock, and you could reach it from the side of the car.

[Mepsipax1]

Unfortunately I've not managed to find the thread, I've searched for at least a couple hours now. But in the morning I'm going to see if I can park one side on the kerb and try scuttle under a little to check it properly.

[SW6Steve]

This is what I was looking for, but not sure if its the same symptoms as you have.

https://f30.bimmerpost.com/forums/sh...ight=undertray

Worth a check!

[Mepsipax1]

Awesome thank you, as far as I can tell wind doesn't change the sound, only road speed but if those two pieces are jiggling together due to road vibrations then I'd imagine that could be the culprit.

I'll check it out in the morning, try some stuff and see if it changes anything.

[Mepsipax1]

So I've tried putting some foam pads between wheel arch trim, I've also put a bolt through the two pieces of undertray so they're stuck together but the noise is still there.

I have also recently noticed that there is a click when braking for the first time in a given direction but it doesn't happen again until direction is changed, might be linked although this sounds like its coming from the rear wheels somewhere. Started happening within the last few days.