Strange noise (faint jet engine)

[echo_mike]

Hey all,

Lately I've been noticing some strange noise from what appears to be coming from the rear end. The noise sounds like a continuous faint jet engine/turbine but seem to be coming from the rear (I can still hear the turbo whistle as usual from the engine bay so that's not the cause) The noise pitch doesn't change with the speed. The noise seems to be heard on all surfaces from around 70km/h (40mph) onward and fairly prominent at 120km/h (75mph). The car drives great, excellent power and handling, no issues with the traction to the rear wheels (haldex seems to be kicking in ok).

I'm currently at 90,000km (56k miles), recently completed service with the new water pump and thermostat as well as the new ribbed ac/drive belt (all services up to date as per Audi spec.). Haldex service has been completed at 45,000km and gearbox at 60,000km. The rear brakes are still original however Audi tells me there's 18mm left and still all good. Tyres are at around 4.5mm (michelin PS4). I haven't physically checked the bearings but I can't hear any typical whirring/thumping noise as expected from the worn bearings.

The noise is really starting to get annoying so I was hoping to get some suggestions on what could be causing it? Anyone experienced anything similar? Any advice?

Many thanks

 

[J0N]

I ‘think’ mine might be doing the same, best way I can think of to describe the noise is like a flying saucer from an old UFO movie lol, it seems to change on different road surfaces too.

This is my second 8V S3, a 2019 and I’ve only had it since December. It has a year of Audi warranty so I’m not overly concerned at the moment and after all the time my previous car spent at Audi I’m not ready to be without the car just yet.


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[echo_mike]

Yeah I also get the ‘UFO’ noise on new flat roads but that’s coming from the tyres.

I wonder if a failing haldex differential would make jet/turbine noise? Diff bearings? CV joints? Driveshaft?

Any ideas? Cheers

 

[J0N]

I initially thought tyres but I get the same noise on Summer Pirelli P-Zeros and Winter Bridgestone Blizzaks, both sets 235 35 19. Unless it’s just a characteristic of these cars?

My Haldex servicing is up to date but I know Audi don’t do anything with the pump filter…..


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[northpole]

check the clearance of the dust shields behind the brake disks... a little stone can create this noise, but if something hit the shield a bit to hard, it can touch the rotating disk resulting in a weird noise that only is audible at a certain speed.

 

[J0N]

check the clearance of the dust shields behind the brake disks... a little stone can create this noise, but if something hit the shield a bit to hard, it can touch the rotating disk resulting in a weird noise that only is audible at a certain speed.

I just re read this (I’d just finished a night shift this morning) and it definitely makes sense, this could explain the differences in the noise on varying road surfaces too? Is this from experience?


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[northpole]

Yes I've had this on several cars with multi link rear suspension.. and even once on a simple mk4 gt tdi with a solid beam rear axle... once a stone gets in between the brake disk and the shield, enter weird noises you can't pin point. Thing is you can bend the shield out of the way easily and bend it back. Without any damage.

 

[J0N]

Got to be worth a look, I doubt there’s anything in there but there could certainly be a bit of contact…..


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[echo_mike]

Yeah definitely worth a look. Might jack the car up and see if I can spin the wheel and listen for any grinding noise. Cheers

 

[J0N]

Only trouble with that is the rear diff won’t let you spin the wheel freely, I reckon I’ll have the wheels off over the weekend.


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[echo_mike]

Agh crap, you're right... I'll have to have a good look from all angles than and hope to find something. Cheers