[bnaccs]

Hi all-
Today I was driving 78 mph when all of a sudden traffic came to a halt. My abs went off and I hear my Volt skid but it performed flawlessly. Anyway,after getting off the highway I hear a rattling sound when moving 5-10 mph when the car goes into regen until I apply the brakes. It is like the weird system check sound I hear sometimes when pulling in my garage or to a stop sometimes . I put the car in park and pressed the brake peddle all the way down and the car makes that weird mecanical( I never knew it would do that)sound but louder. Any thoughts?

 

[voganni]

The sound you're describing sounds like the brake accumulator pump. Also does it right after turning the car on for 15 seconds or so? It maintains hydraulic pressure boost. As for the rattle, not sure.

 

[bnaccs]

I guess rattle is the wrong word. It's like the brake accumulator sound but much more muted.

 

[driver779]

Just curious, did you have any sub-zero freeze the night before, or left the vehicle in freezing conditions? I had something similar and it was due to large chunks of lovely north-land Minnesota temperatures resulting in considerable ice buildup from driving in snowpack.

I also had a Silverado that suffered from a similar fate after a similar situation as you described above. Fix was finding a leak that led to the hydraulic pressure drop in the system.

-Hope you findout what it is! Best of luck to ya

 

[bnaccs]

We had sub zero temps a few days before. The car is filthy and has been driven through slush and muck for days.

 

[Prohidium]

Could be ice formation or chunks that are moving around when braking. Park in an underground garage for a,bit of a thaw perhaps and see if the noises go away.

 

[canehdian]

During the beloved polar vortex and perpetual frozen death, I developed some ice chunks under the car somewhere. I'm thinking in the gap between the rockers.
It would break loose and rattle around a while until it got splashed with some slush to cement it back in place.
If you park outside it could be similar.
If you have a garage, try warming it up above freezing and let the car melt a bit and see if it goes away.