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Discussion Starter #1
On my new Volt 2019 (december), I hear, since 1 week, a sustained whistling/roar noise while the car is slowing in low mode, from 25 to 0 km/h. It's especially loud around 12 to 10 km/h.

Not sure how to exactly explains the noise. Kind of like a tuba/trombone. Very annoying.

I first thought it was due to very cold weather, but today it's minus 10 celsius and I hear it plenty.

What is it ?

I have a meeting at the chevrolet garage next wednesday.


Thanks,

Patrick
 

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Are you sure it's not the pedestrian sound? That's about the range in speed that it activates

Sent from my XT1635-01 using Tapatalk
 

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I very occasionally have a low rumble in my 2017 as you describe. It turns out it is the vacuum pump that supplies vacuum to the brakes. But it's very rare that I feel/hear it. Maybe your brake vacuum pump is working overtime due to a vacuum leak somewhere?

Mike
 

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Discussion Starter #4
It's not the pedestrian sound.

@MikeyCVolt, interesting. Vacuum pump and vacuum leak, is it something that should be fixed ?

I only hear it on cold weather. And now it's cold, and it's less noisy that it once was.

Is it possible that it can auto-fix ?

Thanks!
 

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It's not the pedestrian sound.

@MikeyCVolt, interesting. Vacuum pump and vacuum leak, is it something that should be fixed ?

I only hear it on cold weather. And now it's cold, and it's less noisy that it once was.

Is it possible that it can auto-fix ?

Thanks!
You could check the rubber hoses around the brake fluid reservoir. I'd know where to look on a standard brake booster but I've never inspected that area of the Volt so I don't know what to tell you to look for. I guess maybe trace the vacuum hoses leading into the area under the brake fluid reservoir and see if any are loose, cracked, or cut. It might not be that. When it happens occasionally on my 2017, I can feel a slight pulsing of the brake pedal at the same time as the noise. When it is happening, if you can put your foot lightly on the brake pedal and you feel it vibrating a little, you know that's it.

Mike
 

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Could you just be hearing the (I think) inverter converting the AC power from the motors back into DC to feed into the battery? To me it almost sounds like an electronic 'whirrrrr' type sound. The volume changes in response to the amount of power it's handling. The sound also seems to be a lower frequency on decel than on accel.
 

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Could you just be hearing the (I think) inverter converting the AC power from the motors back into DC to feed into the battery? To me it almost sounds like an electronic 'whirrrrr' type sound. The volume changes in response to the amount of power it's handling. The sound also seems to be a lower frequency on decel than on accel.
That's a possibility too. I didn't think of that because I've never noticed any whir on decel: only accel. And the way Patrick described it (tuba) reminds me of that brake vacuum pump.

Mike
 

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Could be the slightly rusted brake rotors giving unusual noise. You can try slowing down with the regen pedal to see if it happens (without the pads come in contact).
 
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