Buzzing around rear wheel well when stopped

[The_North]

Noticed this issue earlier this year as warmer weather hit, and unfortunately i can never reproduce it no matter what i try. It doesn't seem to be directly related to the air suspension (after cycling it multiple times personally and at the service center). It does happen relatively frequently, maybe more on warmer 20c + days but again it seems to have a mind of it's own. On the inside it sounds like someone is using a gas powered weed whacker nearby. It mainly happens when I'm on the brakes and i haven't heard it in park, it does still sound off as i pull away but it generally disappears as soon as i accelerate. Lastly, no faults reported in service mode.

Does anyone have any idea what it could be? Service center took a look at it even after i was unable to reproduce it on a drive and they still can't reproduce and locate the issue

Sponsored

 

[CyberGus]

Honestly, it sounds like the air compressor, which can be very noisy if the NVH mitigation is not fully intact. It should be loud inside the vault as well.

I don't think there are any other components back there to make such a noise. The drive motors are in the cooling loop, but I didn't think they had their own pumps.

 

[AlDente]

Mine will sporadically make several noises when parked but since I don't live in the garage, no issues. Did you send the video to the service dept for their opinion?

 

[The_North]

Honestly, it sounds like the air compressor, which can be very noisy if the NVH mitigation is not fully intact. It should be loud inside the vault as well.

I don't think there are any other components back there to make such a noise. The drive motors are in the cooling loop, but I didn't think they had their own pumps.

Tech thought the same thing, on a test drive we couldn't reproduce it but the guy was nice enough anyways to take it apart and take a look. Unfortunately they didn't find anything.

Side note, you're right there isn't anything else that could make that noise outside of maybe the thermal components for the rear drive unit, but apparently it's only for heat extraction. Does make you wonder seeing how this issue seemingly started this spring. I did try to push it before giving it to a tech and with the tech, no noise during the runs

 

[The_North]

Mine will sporadically make several noises when parked but since I don't live in the garage, no issues. Did you send the video to the service dept for their opinion?

I did, and i'm glad i had the video, i think they would've thought i was crazy otherwise. I get the feeling this specific noise might be rare? i'm having a hard time finding any other examples of it. Funny thing is, it doesn't do this when i'm parked, only while holding the brake (either through brake hold or manually pressing it)

 

[mongo]

There is an oil pump in the rear drive unit...
... it really shouldn't sound like that though
Nor should parking brake
Oh, if it's an AWD, there is also the locking differential

 

[The_North]

There is an oil pump in the rear drive unit...
... it really shouldn't sound like that though
Nor should parking brake
Oh, if it's an AWD, there is also the locking differential

Interesting i never thought about the locking diff. As for the oil pump, that sound does seem like it would be related to a mechanism like that. i'll keep those in mind, thanks

got word back from the service center that they couldn't find the issue even after inspecting the air compressor and then road tested. I do wonder if the oil pump was failing if it would show an error code in the service menu.

 

[mongo]

Interesting i never thought about the locking diff. As for the oil pump, that sound does seem like it would be related to a mechanism like that. i'll keep those in mind, thanks

got word back from the service center that they couldn't find the issue even after inspecting the air compressor and then road tested. I do wonder if the oil pump was failing if it would show an error code in the service menu.

The oil pumps have LIN communication, so can likely provide some feedback, but I'm not sure what it would cover.

Sponsored