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The noise you are all hearing is the security system arming. You can test this by sitting in your car after you have parked and removed the key from the ignition. Once parked, open and close your driver's door while remaining in the car. Using the key fob, lock all doors. At this point if you open a door from the inside prior to the buzzing, the alarm will not sound. Open the door after the buzzing, the alarm will sound. Definitely nothing to do with the turbo as I have an LS and hear this sound all the time.
 

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I have heard this on my 2012 Cruze as well and like some of you I have cycled the key and it has gone away but not always. A time or two I've had to start it to make it go away. Either way, I would buy the theory of the A/C system to be the most likely. I would say the A/C system is equalizing after being shut off which is completely normal, but some component in these systems on these cars has an inherent noise when pressure is moving "backwards" so to speak as it equalizes, as it would when the system is shut down. The two components that come to mind that might make such a noise would be the expansion valve, as mentioned in other posts, and the compressor or variable displacement control valve on the compressor, as these compressors are of that variable displacement design and could make this noise anomaly as intermittent as everyone and myself have experience since it takes just the right conditions.
 

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Don't know why this would be confusing to anybody. The auxiliary water pump is mounted right up by the head to the left of the turbo, as you look at the engine. It is the black thing that the radiator hose is connected to. It runs for whatever amoount of time to keep the turbo from coking oil in the bearings. Not a big deal unless, later on down the line we find that it is a problem. I had one on a Dodge durango for aft heating that let loose. But lets face it: It was a dodge. (Really does not matter, I am sure it was a vendor supplied part, much like this one probably is)
Pretty confident you are right on this. That's exactly where the noise was coming from the one time I heard it. Oddly, it was after my wife drove the car and I've never heard it do that when I drive it(every day).
 

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I too have heard the noise on my 13 ECO MT. I have noticed that I can hear the noise with the engine running if the AC is on low. When the AC system starts you can hear the same buzzing as in the video. When you turn off the AC with the AC control, the noise goes away. On occasion the noise does not go away when the engine is shut off with the AC on.

To my ear as an EE, it sounds like a coil being pulsed at the frequency of the noise. I suspect that something in the AC system is being modulated by the AC controller and on occasion it does not shut down with the engine as you would expect.

It does seem to be comming from the area of the compressor but I have not isolated it to anything specific.

I did notice that if I turn off the AC prior to shutting off the engine it goes away. It may or may not be an issue. I could think of scenerios either way.

I have not tried the various possible combinations very much. It may well be that other interesting things are possible. I'll probably just try to turn off the AC before I stop the engine.
 

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The noise you are all hearing is the security system arming. You can test this by sitting in your car after you have parked and removed the key from the ignition. Once parked, open and close your driver's door while remaining in the car. Using the key fob, lock all doors. At this point if you open a door from the inside prior to the buzzing, the alarm will not sound. Open the door after the buzzing, the alarm will sound. Definitely nothing to do with the turbo as I have an LS and hear this sound all the time.
so why has my security system only armed 4 times on hot days with my ac on?
 

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I too have heard the noise on my 13 ECO MT. I have noticed that I can hear the noise with the engine running if the AC is on low. When the AC system starts you can hear the same buzzing as in the video. When you turn off the AC with the AC control, the noise goes away. On occasion the noise does not go away when the engine is shut off with the AC on.

To my ear as an EE, it sounds like a coil being pulsed at the frequency of the noise. I suspect that something in the AC system is being modulated by the AC controller and on occasion it does not shut down with the engine as you would expect.

It does seem to be comming from the area of the compressor but I have not isolated it to anything specific.

I did notice that if I turn off the AC prior to shutting off the engine it goes away. It may or may not be an issue. I could think of scenerios either way.

I have not tried the various possible combinations very much. It may well be that other interesting things are possible. I'll probably just try to turn off the AC before I stop the engine.
Exactly. It's absolutely something in the AC system, and only happens when it has been running.

I'm thinking expansion valve - it's from the right area, but I could be wrong.
 

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OK so I asked my Chevy dealer today what that buzzing noise is. They told me that it is the AC compressor. The AC compressor on this car is of the variable displacement type that is electrically controlled.

When the Evaporator gets too cold, the compressor displacement is reduced electronically. This is done instead of cycling the AC clutch. The car still has an AC clutch that is disengaged if the AC is off but it is not used for control.

I find it's most notable with the AC set to cold and the fan speed at minimum. If I increase the fan speed the noise goes away after a few seconds. The noise does fade in and out as you change the fan speed. I believe that the AC control is using PWM control like a FI to adjust the compressor displacement.

As for why the sound continues after turning the car off, they had no comment and I could not get it to do it. My car does do this on occasion but so far I have not figured out any sequence of events to cause it. I would not doubt that just about anything might cause it to stop if it did continue. This might include arming the anti theft system.

Basically they claim it's normal. Bring it back if it gets louder.

I guess I'll monitor the situation
 

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My '13 LT 6spd manual has done this three times. First time I turned the car off with the A/C on. Did what others did and turned key to ON to check idiot lights, saw nothing, then turned the car OFF, and it stopped.

Second time it happened, I was at my hackerspace. Rushed in and grabbed a friend that was there who might be able to pinpoint the location. Couldn't, as the sound slowly faded away.

The third time it happened, I had driven about 45 minutes, but only had the air on about 20 minutes into the trip and turned it off about 10 minutes before arriving. (I only had the air on while driving on the expressway). When I arrived at my destination with the air turned off, the car made the noise. I did the key trick to turn it off. Not sure if that's bad or not.

To the person in post #68 (too lazy to find it and quote it), the reason why it doesn't stay on due to the key turning to position ON then OFF, I'm guessing based on my BS in computer engineering, is that the way they designed the system (if this is normal), is that the ECU looks for a value that is greater (or less than) another, and then turns this solenoid, motor, etc ON for X amount of time (perhaps based on the initial read value). When you turn your key ON then OFF (interrupting the current operation), the ECU reads again, but at this point, the data value it's checking is within the safe threshold, so the solenoid, motor, etc. does not kick back on or stay on. Just my two cents.
The way to prove me wrong is to be able to never get it to come back on after you go back ON to back OFF once you turn your car off, immediately after hearing the sound.

The turbo lube idea was pretty good. But since people with LS Cruzes are saying they hear it to (granted they're hearing the same issue), then it leads me to also believe it is the A/C unit. I have never heard it through the winter, even with defrost on. Only on hot days (I rarely use A/C).
 

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OK so I asked my Chevy dealer today what that buzzing noise is. They told me that it is the AC compressor. The AC compressor on this car is of the variable displacement type that is electrically controlled.

When the Evaporator gets too cold, the compressor displacement is reduced electronically. This is done instead of cycling the AC clutch. The car still has an AC clutch that is disengaged if the AC is off but it is not used for control.

I find it's most notable with the AC set to cold and the fan speed at minimum. If I increase the fan speed the noise goes away after a few seconds. The noise does fade in and out as you change the fan speed. I believe that the AC control is using PWM control like a FI to adjust the compressor displacement.

As for why the sound continues after turning the car off, they had no comment and I could not get it to do it. My car does do this on occasion but so far I have not figured out any sequence of events to cause it. I would not doubt that just about anything might cause it to stop if it did continue. This might include arming the anti theft system.

Basically they claim it's normal. Bring it back if it gets louder.

I guess I'll monitor the situation
Yeah, I was definitely incorrect in my assumption. I never use the AC and the one day I did I heard the noise too.
 

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If you have the 1.4 the sound is most likely, in English, the car cooling the turbo down. It has an internal system that keeps it from overheating and it makes a high pitched buzz.
 

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Hello all,

I am sorry to hear you guys are experiencing this concern. You can always private message us your name, VIN, mileage, phone number, and address, so we can look further into your concerns. Look forward to hearing from you.

Erica Tiffany
Chevrolet Customer Service
 

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It's not even a concern. From what we've seen in this thread alone, it happens to every Cruze, so there isn't really anything to look into. Nothing is wrong with the car, it's some sort of pump that runs after the car turns off. I've even heard mine with the car running.
 

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The fix for the buzz after turning the vehicle off will be a re-program and it will be out soon. I will post when it comes out and give the PI or bulletin number so you can give to your dealer.
 

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Gfxdave99, you're correct, but in this case, i'm not so sure that he was wrong. I've heard mine do it too, and it definately doesn't sound like the fan!!! what i'm hearing sounds like a hgher pitch noise than the hummm of the fan. but what is it????? - Dan
Video of my cruze doing this, seems like the thermostat to me Cruze noise - YouTube



Sent from my iPhone
 

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It is the A/C compressor. Only happens under the right conditions at engine shut off. Stay tuned.
do we know what exactly what with the a/c we are hearing or what the perfect conditions are. mine has only done it about 4 times and the one time i made an appointment of course it didnt make the noise. thanks for your help on this matter!!
 

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do we know what exactly what with the a/c we are hearing or what the perfect conditions are. mine has only done it about 4 times and the one time i made an appointment of course it didnt make the noise. thanks for your help on this matter!!
I was told that if the blower is turned off and the key is turned off within 10 seconds and the pulse width of the solenoid inside of the a/c compressor is between 45-58%, it can cause a buzz like a reed for 10 seconds to 10 minutes. Ponder that one. :wacko:
 

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No. You can hear that pump running after shutting the car off too and it's definitely a different noise than we are talking about here.

Link to (that) noise: http://www.youtube.com/watch?v=pJZNwTpipuU
Hi all,

Since yesterday morning my 2013 ECO 6MT with 4500miles has been making a buzzing noise as well. I knew I had read something about this on the forum here and so checked it out this morning.

For background, I have never heard any buzzing noises before. I only started hearing this since yesterday. It is certainly not the same as the metallic buzz most people report on here and seen in the videos. However, mine matches exactly what jblackburn shows in the video in this post.

I hear it first thing in the morning (cool car in the garage) when I turn the key to ACC. I popped the hood and I could hear it from somewhere near the passenger side engine bay (near the turbo). I don't hear it after turning on the car (possibly because engine is louder). I do hear it though after a drive and switching the car off. I need to go and check again now after the car has cooled down from the drive.

jblackburn or anybody else have any idea about this particular sound that you show in this video?

I am concerned as I have only just started hearing this sound.

Thanks.
 

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That noise is a booster pump that builds up vacuum pressure for the brake booster assist when the engine is off or not providing enough vacuum (e.g. turbo under boost or at idle on a cold morning when the valve overlap allows for very little vacuum).

It's normal for me to hear it when coasting to a stop in a parking lot with the engine idling, or putting my foot on the brake sometimes before starting the engine.

If you hear it pretty often, perhaps you have a bad check valve near the brake booster leaking vacuum pressure and/or a vacuum leak in a hose somewhere. If you ever experience problems with braking in the morning with a cold engine or in reverse, take your car in immediately. Otherwise, I wouldn't worry about hearing the noise too much.
 
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