# Robotic brake noise...part 2?



## titan2782 (Nov 4, 2011)

There is another thread on this, but no one posted an audio file. I've been noticing this noise in the last 2 weeks and it's happening all the time now. when the brakes are applied while the engine is at low speeds or idle (may occur all the time, but can't tell due to road noise) there comes a robotic servo noise that will continue for 2-3 seconds even if I take my foot off the brake. It happens EVERY time i put pressure on the brake pedal and if I pump the pedal, I can get the noise to continue on forever.

I'm at just under 45k and i've only heard this noise in the last few weeks so it isn't "something these cars do". It's very noticeable inside the cabin with windows rolled up and even when music is playing (low volume).

Ideas? Maybe vacuum issue or low fluid? I haven't investigated as of yet.

Audio 1: https://www.dropbox.com/s/31ws6avmbjgnsgn/Voice 002.mp4
In a drive thru (kind of noisy outside)

Audio 2: https://www.dropbox.com/s/e80ksay5p1cynup/Voice 003.mp4
In my garage with car running 

Have to turn the volume up.


----------



## kobowm (Jan 22, 2013)

They are called electric pumps...... They pump brake fluid to the brakes.... Its 100% completely normal.

Sent from my Galaxy Nexus


----------



## titan2782 (Nov 4, 2011)

No, it isn't normal. During initial start up from 1 mile until ~44k miles the robotic noise happens during and only during the initial key switch. Now it happens both when I press the pedal AND release and does not matter if the engine is running or not.

I topped off my fluid, it was about 1/2 way but that didn't help. If I remove the plug from the valve on the brake booster, there is no more noise and brakes work ok...at low speed. Since I only have manuals for the engine, I can't tell you if that means anything or not (probably doesn't). 

Taking it in to have it looked at. Will report back.


----------



## phantomknight321 (Jan 29, 2013)

I hear this quite often as well, but i only have almost 16k miles. Let me know if you find anything out about it


----------



## bryanakron40 (Nov 8, 2012)

It almost sounds like the a valve fluttering in a vacuum hose, too. Kind of like a pcv valve or an evap solenoid.


----------



## titan2782 (Nov 4, 2011)

*kobowm *is correct in saying it's "normal" however, it's only been normal during first start when I flick the key to the on position all this time. I always thought it was the fuel pump (since all my other cars did this as well). Didn't realize it was the brakes. 

I'll report what they tell me.


----------



## titan2782 (Nov 4, 2011)

Alright so the 1.4's have an extra vacuum pump to compensate. The service tech said I should bring it in. Have to wait for my PCV pipe to come in before I do it so it will be next week sometime.


----------



## jblackburn (Apr 14, 2012)

I heard this noise once when I turned off the car and turned it back on. 

Yeah, shouldn't be doing that all the time. 

A lot of turbo VVT motors have these pumps to compensate for there being a total lack of vacuum at a cold, high idle with the timing off "normal" settings. 


Sent from AutoGuide.com App


----------



## jblackburn (Apr 14, 2012)

HOWEVER I wonder if the pump is running just because you have a vacuum leak to make up for the lost vacuum to the brake booster? You said youre waiting on a PCV hose? Perhaps that's all it is and it will stop as soon as you fix that problem. 

Sent from AutoGuide.com App


----------



## titan2782 (Nov 4, 2011)

jblackburn said:


> HOWEVER I wonder if the pump is running just because you have a vacuum leak to make up for the lost vacuum to the brake booster? You said youre waiting on a PCV hose? Perhaps that's all it is and it will stop as soon as you fix that problem.
> 
> Sent from AutoGuide.com App


I'll check if that's the issue, but I doubt it. I've sealed it all up (maybe) and the pump is running even when the car is off which i know for a fact didn't happen because I regularly push my car out of the garage when cleaning it (I don't like to start it just to move it 15ft then turn it off).


----------



## jblackburn (Apr 14, 2012)

I would still suspect the leak. I turned my car off as I coasted into a space with my foot on the brake. When I flipped the ignition back on to eject a CD, that's when I heard the vacuum pump. 

In any case, guess you'll know soon!


Sent from AutoGuide.com App


----------



## 20131pz69 (Oct 22, 2012)

titan2782 said:


> Alright so the 1.4's have an extra vacuum pump to compensate. The service tech said I should bring it in. Have to wait for my PCV pipe to come in before I do it so it will be next week sometime.


might I suggest a catch can delete prior to the service? Don't want the techs to think u did something that caused it & make the service difficult ...


----------



## Chevy Customer Care (Oct 29, 2011)

titan2782 said:


> Alright so the 1.4's have an extra vacuum pump to compensate. The service tech said I should bring it in. Have to wait for my PCV pipe to come in before I do it so it will be next week sometime.




titan2782,
I would like you to keep me posted on the progress with your dealer. If you have any questions please feel free to contact me. 
Thank you,
Stacy Chevrolet Customer Service


----------



## jblackburn (Apr 14, 2012)

Titan,

This is what you're hearing, right?

I coasted to a stop after shutting the engine off. After stopping, then hitting the brake pedal one more time, the pump started running, and will every time I hit the brake pedal after the car loses vacuum.


----------



## titan2782 (Nov 4, 2011)

jblackburn said:


> Titan,
> 
> This is what you're hearing, right?
> 
> I coasted to a stop after shutting the engine off. After stopping, then hitting the brake pedal one more time, the pump started running, and will every time I hit the brake pedal after the car loses vacuum.


Yep. I just encountered a big vacuum issue so I'm still taking it in for a look. Does yours do it when you release the pedal also?


----------



## jblackburn (Apr 14, 2012)

Only after the 2nd-3rd time after the engine is shut off. Otherwise, I imagine it only turns on if the turbo is boosting or at a COLD idle when there is no vacuum. 

I don't hear it when normally idling and hitting the brakes. May be that the engine is louder than it, or that, like I believe, it's just not running when the engine is idling and providing enough vacuum for the booster.


----------



## jblackburn (Apr 14, 2012)

Interesting note: the power steering still works for a brief few seconds as the car is coasting and the engine shuts off/is turned off. Perhaps until you actually get to a stop. 

I thought that was cool. 


Sent from AutoGuide.com App


----------



## titan2782 (Nov 4, 2011)

Documentation says they checked it out and found it to be normal operation. But, I haven't heard it since I got the car back.


----------

