# Brake Assist Pump whirrs when ignition on



## Do_Will (Jul 15, 2016)

2012 Cruze Eco 60k miles.

I started hearing a new whirring noise from under the hood.

With the help of a friend, I tracked the noise down to the Brake Assist Pump. It seems to start running when I turn ignition to ON. It stops after engine starts. When I pump on the brake, I can hear it starting and running briefly (which is normal and expected). Brakes are fine.

I can swear that noise was not there for the previous 60k miles. Why is it whirring like that with the ignition on? Anyone else has the same issue?


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## jblackburn (Apr 14, 2012)

Might be a bad switch or check valve that holds in vacuum pressure. The switch on the line to the pump was a subject of a recall for automatic Cruzens at one point, and has been known to fail in the past.

It should not run simply when the key is turned on; it should only run when the brake booster needs a vacuum source (e.g. brake pedal pumped).


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## ChevyGuy (Dec 13, 2014)

I'm wondering if the pump has gotten noisy. If I listen for it, I can hear it, but it's really hard to hear when you're in the car and everything is closed up.


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## carbon02 (Feb 25, 2011)

With the brake booster fully depleted of vacuum, and a rock hard peddle with the engine off.. Engine turned to on, but not running.. The service manual states between 10-13 seconds to fill the brake booster with vacuum. If it's running longer than this you have a leak.

I researched this detail when I did my own 2012 Brake Switch recall. If the brake switch recall was done by pulling the switch out of the plastic hose assembly, there's a good chance that maybe the plastic hose is cracked and leaking. 

It took me over 30 minutes to carefully get the replacement switch to clip into the plastic housing port that is part of the brake booster line. With this only paying a technician 15 minutes, I'm guessing some switches were installed and hoses potentially cracked, or stressed enough that they will crack latter.

GM now no longer replaces just the switch, if this is now done under recall the entire line is replaced. I'm not sure if this was done because of a parts sourcing issue, or if it was done because technicians in a hurry were cracking the vacuum line causing future problems. 

There's a youtube video of someone replacing the cruze vacuum pump. He replaced the pump only to find his line was leaking vacuum. The pump will burn out if it's continuously running. That is a $100 part. The hose assembly is another $60-$70. Both are ACDelco only parts, but I believe they were available at rockauto. Do a search based on part numbers, which you can find from GMPartsdirect or your favorite GM online parts catalog.


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## Do_Will (Jul 15, 2016)

Sorry, I didn't respond to this chain earlier. I just got lazy and learned to live with it. Not sure if it is related or started with the same symptom that is the reason for this thread - I have been experiencing occasional brake pedal stiffening. It happens sometimes when I have to accelerate and brake immediately. 

Anyway, finally I am getting myself around to take this seriously. 

Looks like the pump actually stops once the engine starts. After that, I can see that it switches on when I pump the brake pedal a couple of times, which seems to be the normal operation.

I looked around the pipes and don't see any damage to the pipe itself. With key on and engine off when the pump is running continuously, I felt around the connections and didn't feel any leak. Don't know if it is a sensible way to test for leak.

If I disconnect the wires going to the micro-switch on the pipe assembly, with key on and engine off, the pump runs for about 10 seconds and stops. Is this normal behavior? what is happening in this scenario? How does it know to switch the pump off if I have disconnected the switch? Is there another sensor/switch for this purpose? Or, am I off ?

I am assuming that the switch remains closed when key is on and engine is off. Could the switch itself be bad ? It was replaced as part of the recall. I am tempted replace the switch again and see if that fixes the issue. 

Can I get some expert opinions, please?


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## jblackburn (Apr 14, 2012)

Do_Will said:


> Sorry, I didn't respond to this chain earlier. I just got lazy and learned to live with it. Not sure if it is related or started with the same symptom that is the reason for this thread - I have been experiencing occasional brake pedal stiffening. It happens sometimes when I have to accelerate and brake immediately.
> 
> Anyway, finally I am getting myself around to take this seriously.
> 
> ...


I would try replacing the switch. It's been known to fail, even after the recalls have been done on some of them.

I believe the 10-second run time is probably a default operation because the switch is disconnected. The brake pedal changing when you accelerate and then brake is an indicator that the booster doesn't have a source of vacuum.


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## ChevyGuy (Dec 13, 2014)

Do_Will said:


> Looks like the pump actually stops once the engine starts.


Somewhere in the system must be a check valve so the engine can supply vacuum, but not "consume" it. If the switch doesn't fix it, I'd be checking that check valve.


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## Robby (Mar 1, 2013)

There is a vacuum leak somewhere leading to or at the booster, or the one way check valve......even the booster itself.
A system operating normally will hold vacuum for several days, sometimes even longer.

The brake vacuum system on the 1.4 uses a electric pump to augment intake manifold vacuum since a turbocharged engine will pressurize the manifold when on boost.

Since your pump runs constantly unless the engine is running, it is showing you that it cannot keep up with the vacuum loss unless the engine is running to provide additional vacuum.
Continued operation will burn the pump out because it is running far more than designed during normal driving.....you just can't hear it (yet).

Real diagnosis for a vacuum loss is required......it won't get well and continued operation will end up as a 'No Assist' at all situation.

Rob


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## Do_Will (Jul 15, 2016)

It was indeed the micro switch !! Replaced it this weekend and it resolved both the issues - (1) pump running with key on and engine off and (2) the braking loss.

Seems like after the recall, they had replaced it with another one from the faulty batch. Wonder why they perform a recall if they don't really fix the issue.

Robby: I too was not convinced that it was the micro-switch, but decided to try it out because, apparently, it is known to fail even after the recall. And, that was something I could do myself without going through the pain of taking it back to the dealership and explaining the situation to them.

A follow up question - The switch kit came with the two tubes - one connecting to the manifold and other connecting to the pump. I couldn't replace the tube connecting to the pump because I couldn't figure out how to remove it from the pump. Can someone tell me how that connector works? How do I release it from the pump? And, do I just push the new one onto the pump?


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## carbon02 (Feb 25, 2011)

Do-Will-

Search Youtube for a video on "Cruze Vacuum Pump replacement" You'll find someone that replaces the switch, only to replace leaky lines, followed by a pump that burns out. 

I can't remember if the connection at the pump is a push together and pull connector, or if there's a release piece of plastic to be removed first with a pick or screwdriver, followed by a squeeze and pull action. 

The video is out there on Youtube, I remember watching it before I replaced my brake switch. Which I see you found.


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## Do_Will (Jul 15, 2016)

Just a side-note. This car had a strange squeal/whistle sound that used to originate from somewhere under the hood on hard acceleration and would last for 3-4 seconds. I had learned to live with it. Guess what ! That disappeared with this switch replacement that I did. Guess it was all related - the brake loss, pump whirring, squeal/whistle on hard acceleration. 

One micro switch so many issues. I am still kinda disappointed with Chevy for performing a recall with faulty part and are not willing to correct it.


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## guzunov1990 (Nov 18, 2021)

Sorry to bring back this topic to life, but I have a 2016 Chevy Sonic 1.4T turbo, which is having the same issues. Can someone point me to the "switch" that goes bad and needs to be replaced?

I've searched for it, but it doesn't really come up online?


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## jblackburn (Apr 14, 2012)

guzunov1990 said:


> Sorry to bring back this topic to life, but I have a 2016 Chevy Sonic 1.4T turbo, which is having the same issues. Can someone point me to the "switch" that goes bad and needs to be replaced?
> 
> I've searched for it, but it doesn't really come up online?


It's sold as part of the whole brake booster vacuum tube.






2012-2020 Chevrolet Sonic Power Brake Booster Vacuum Hose 95391441 | GMPartsDirect.com


2012-2020 Chevrolet Sonic part # 95391441 - Power Brake Booster Vacuum Hose




www.gmpartsdirect.com


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## guzunov1990 (Nov 18, 2021)

Thanks @*jblackburn you're the man!

I'll post a video of what's happening a minute but it sounds a lot like what was going on here.*


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## guzunov1990 (Nov 18, 2021)

Here's a video of the issue. Every time you press the brake pedal this sound happens...

Here's a photo of what I think is the part you mentioned above?


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## jblackburn (Apr 14, 2012)

guzunov1990 said:


> Here's a video of the issue. Every time you press the brake pedal this sound happens...
> 
> Here's a photo of what I think is the part you mentioned above?


It's normal for the vacuum pump to run at idle, and that should mean that your vacuum switch is working.

What ISNT normal is a stiff brake pedal that takes a lot of force to slow down or the sensation of no brakes on high idle/in reverse in the morning. That's where the brake assist pump should be stepping in, and the switch isn't telling it to.


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## guzunov1990 (Nov 18, 2021)

So that sound is fine? I'm quite sure it wasn't there, but maybe I'm mistaken as I was not out of the car when it was started.

So the deal is that every time I push the brake that sounds is happening...?

The pedal feels fine, the car stops fine, brake assist is definitely working, but I do not think the sound is normal?


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## jblackburn (Apr 14, 2012)

guzunov1990 said:


> So that sound is fine? I'm quite sure it wasn't there, but maybe I'm mistaken as I was not out of the car when it was started.
> 
> So the deal is that every time I push the brake that sounds is happening...?
> 
> The pedal feels fine, the car stops fine, brake assist is definitely working, but I do not think the sound is normal?


Pump sounds normal to me.

I'm not 100% sure if it is supposed to run every time you press the brake or there's a vacuum reservoir/check valve setup that should prevent it from running every time. It seemed like my old 2012 needed a few pumps of the pedal before the pump triggered.


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## guzunov1990 (Nov 18, 2021)

Well, I've booked a mechanic to take a look at this "issue" tomorrow, as I would rather fix the issue (if there's an issue) and not throw money at it.

I do appreciate the assistance *jblackburn! *I'll post updates once I know what's the full story


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## guzunov1990 (Nov 18, 2021)

Random googling for "every time you press the brakes the vacuum pump" gave me this thread... not really the same car, but maybe the same principle?









Vacuum pump runs every time I press the brake pedal?


I've had my 2018 JLU for just a few months, and I notice that the brake vacuum pump runs every time I press the brake pedal. I can start the car in the driveway, sit there with engine idling, press the brake and the pump comes on. It stays on for a few seconds after I let the brake up. If I wait...




www.jlwranglerforums.com





Maybe this is normal...


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## guzunov1990 (Nov 18, 2021)

So it turns out that sound is coming from my ABS pump. My mechanic is not overly certain that this is normal, so we will do some digging. No ABS lights, no issues braking.
The mystery continues


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