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Sound from rear of car

2565 Views 17 Replies 8 Participants Last post by  Dara
I 've had my 2011 for nearly 3 years and I know this sound is normal, but never really cared what it was until now. Usually within the first few minutes of my morning drive, there is a sound, sometimes two or three times which sounds as if you ran over a piece of rubber and it hits the wheel well. I always figured it may be something to do with the gas tank pressurization. Kind of like a low pitched thump or thud type noise. Pretty distinct noise, I'm sure any gen 1 owner will know the sound.
Anyway, what is it for sure???
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Common reoccurring noise for many in the Gen1 Volt. Most likely what you are experiencing is from the rear spoiler. The plastic of the spoiler is extremely close to the body of the car where it is attached.

With the thermal expansion coefficient for the plastic being different than the metal hatch, there is a point at which the contact between the two materials causes a slip, which generates the loud thud/pop noise.

I remember the first time I heard it, I thought my rear window had cracked! There is an older thread that mentioned a fix, I believe it involved the dealer removing the plastic panel on the hatch and tightening the mounting screw on the spoiler. Never taken the time to try to remove the cover to find out.
Yep, always on the right rear of mine too. Sometimes if the temperature is right, I can get it to pop with a little pressure, maybe you can test yours that way. I've also had it happen in a car wash on a hot day... guess the water cooled it down enough.
The spoiler expanse sound is a "pop" sound like an acorn hit the back of the car. The gas tank pressurization system (in the right rear) is a more rhythmic sound, like a small buzzing/banging sound.
I would have concern for any compressor making a banging sound. I've heard the Volt's fuel tank compressor many times and would never describe it as a 'bang', always a hum/buz (like a small tire compressor but muffled). I've also only ever heard it from the outside of the vehicle, but I suppose that varies with volume inside the cabin.
Did you leave you mother-in-law in the back?
No that would crested a constant noise "yak, yak, yak, nag, nag, nag, yak, yak..."
Or awkward silence, lol!
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