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Low moaning sound coming from my C-max

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9 replies to this topic

#1 OFFLINE   Aztoothman


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Posted 31 January 2018 - 09:18 PM

My 2013 C-max has 82000 miles and in the last 3 months has started to display a intermittent low moaning sound from what sounds like the underside of the vehicle. It comes and goes as the speeds change. It will go away temporarily if i let up on the throttle and then come back as I accelerate again. The noise is louder when accelerating in the lower speeds. Has anyone else had this problem ? And if so, is it an issue that needs attention ?


John in Arizona

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#2 OFFLINE   Redshift


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Posted 01 February 2018 - 12:53 PM

I have a 2015 and it's always done that. Unless it does it constantly, the dealer can't do anything.

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#3 OFFLINE   obob


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Posted 01 February 2018 - 02:18 PM

Welcome Aztoothman.


I don't know if this is your noise but it seems synergistic with your description.  I have what I would call a drone sound when the internal combustion engine is running (ICE) and it is regeneration mode.    When I first bought the car it did not have it, but after one of the early software updates it started.  It may be they changed things to be more aggressive with recharging the battery.  I am used to it but if it did that when I tested the car I would think the car was noisy.  I am not sure if the later models have it but it is my understanding is that it is common on the 2013s. My drone/moan has slowly changed louder. Regeneration of the HVB(high voltage battery) mode can be identified with an up arrow thingy on the empower screen.  This condition probably is mentioned in one or more message threads on this forum but it not a situation that is worrisome to me.  


What is of concern is the 2013 transmission problems which there are also message threads discussing that.

Edited by obob, 01 February 2018 - 02:21 PM.

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#4 OFFLINE   fbov


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Posted 01 February 2018 - 04:29 PM

Welcome as well!


I'm not sure what obob is describing, but I do know what you're hearing. I first heard it visiting my daughter in Vermont, Thanksgiving 2014. Occurs rarely enough to ignore; I need a hill and just the right speed... and it might happen. 


Some owners have it worse and have tracked it to the cabin noise suppression system. Some of them have disabled the microphone, others pulled a fuse... problematic as I believe it uses the car's audio system. I treat is as a rare event and ignore it when it happens. 


HAve fun,


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#5 OFFLINE   Aztoothman


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Posted 13 February 2018 - 09:40 PM

Thanks for the input. At least others have been experiencing this unusual noise. I'll just keep driving it and see what happens. I have to say that I don't understand why the C-max isn't more popular. Of all the cars I have owned over the years, my C-max is more fun to drive, and more of a car then any of the others.



John in Arizona

#6 OFFLINE   Ed Venture

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Posted 09 March 2018 - 07:16 PM



I had what I believe the be the EXACT same sound as you describe it.  Mine also came and went and was never identifiable enough to get it to the point where the dealer would be able to reproduce it. 


I say "had" the problem because yesterday the transmission gave out.   It erupted into an extremely loud grinding noise and warned my wife to pull over and have it towed (which she did).   It was dropped off at the dealer last night with the failure coming at 62,432 miles.  Unfortunately I am now getting the official run-around from them.  They agree the CVT is broken to some extent, but they are claiming that depending on WHAT broke and HOW it broke that it MAY not be covered by warranty.  Of course, there is a lot of data on this forum (and in the warranty manual) to support otherwise, but it looks like I will have to dig in for the impending battle.  I digress.


I did FINALLY mange to get a recording of the sound in question and have posted it in the link below.  NOTE:  YOU MUST LISTEN TO THE CLIP WITH HEADPHONES OR EARBUDS!!!  You will NOT be able to really hear just how bad it is with a standard PC speaker.  The moan/drone is a low frequency and is not well represented on something like a PC notebook speaker.  When you put the headphones on, the moan is deafening - trust me.


Anyway - the only time I could reliably reproduce it was when it was in near freezing conditions which were VERY hard to replicate here in Texas (I imagine the same for you in AZ) so I know just how difficult it was to pinpoint this issue.


As a side note, my father is a retired Ford Powertrain Engineer.  I spent a good part of my youth "assisting" him with identifying Noise, Vibration and Harshness (NVH).  He would shout out commands to me and my brother in the back seat, "Where is that coming from?! Which side?!  Lets see if how it changes with speed... Can you still hear it?!"  It would make my mom nuts and I am now permanently cursed with "hearing" all sorts of things in cars that most consumers wouldn't even notice which, in turn, now drives MY wife insane.  Thanks dad!


Link to Video/Audio File:



EDIT: Link to Video/Audio of transmission sound just after it happened (again - use headphones or a good speaker - phone or notebook speaker won't do it justice):







Edited by Ed Venture, 09 March 2018 - 08:38 PM.

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#7 ONLINE   djc


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Posted 11 March 2018 - 12:33 PM

I had this in my 2013, only under certain conditions: cold weather, lower speeds (under 50), ICE running with partial engine load (such as going uphill).

I am sure it was two things: a small powertrain noise,  made much worse by the noise reduction system intended to mask it.  it was almost completely fixed by a firmware update the dealer did over a year ago when I had it in for something else. 

You may be able to diagnose by pulling the audio system fuse.  See other threads on this. 

#8 OFFLINE   ptjones


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Posted 11 March 2018 - 01:05 PM

What kind of gas mileage are you getting? When I had the trans issue it made a more grinding higher pitched sound, interesting the noise goes away when letting off the gas. :headscratch: 



#9 OFFLINE   jestevens


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Posted 12 March 2018 - 06:27 AM

The first time I ever drove a C-MAX I actually hated the car because someone had let it sit and the battery was very low - the engine was so whiney running at high RPM trying to charge up the HVB.  I'm sure it's not the issue you describe but I thought I would mention it.  I'll give a listen to the audio anyway since I own a 2013.  I know there are definitely some harmonics from the powertrain but I sort of like them now.  I am driving mostly around town with occasional highway trips. I've got a little over 80K mi so I might just trade the car in if the transmission ever goes out..so far so good though.

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#10 OFFLINE   adria0425


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Posted 17 April 2018 - 02:26 PM

Hi I have a 2013 c max and it is making a very loud noise once I go past about 35-40 mph and there is a slight vibration that i feel on the bottom of my feet as I am driving. I am not sure what it could be But different mechanics tell me different things so I am not sure what to do. The noise on the video that is posted on here sounds similar so I am thinking it could be the transmission based off of that post with the videos. 

Thank you!

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