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Discussion Starter · #1 ·
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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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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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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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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Discussion Starter · #5 · (Edited)
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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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?
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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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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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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Discussion Starter · #9 · (Edited)
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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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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Discussion Starter · #11 ·
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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