Hum coasting from 30 to 20 - ABS?

[DesertDenizen]

My new 2012 Leaf makes a humming noise first thing in the morning if I get to around 30 mph and then remove my foot from the accelerator. The dealer said the ABS system does a little diagnostic test when first used in the morning and this may be what I am hearing. I never heard it on my 2011 Leaf. I do not hear it for the rest of the day. It has been getting into the 20s at night here, which is unusual. Any thoughts? It does not seem to be a serious concern, more of an enigma.

 

[Computerizer]

I have noticed when I'm just leaving work lately (temps in the mid 30s) that I hear a bit of a noise that might be described as humming, though it sounds more to me like a light mechanical rubbing. My immediate thought when I hear the sound is "cold brakes". Could be what you're talking about.

 

[essaunders]

I'll jump into this 'strange sounds' thread. My 12 leaf made a strange sound for the first time.

I left work and it was about 14F. My car showed 3 temp bars. Everything seemed to run fine, just I noticed a "warble" below about 30mph. It was loudest on deceleration (coast down or braking) and the tone was directly tied to speed.

As I slowed from 40mph (for example), this what I heard;
I started hearing the sound over the wind and other background in the mid to low thirties. It was really noticeable at the mid to high twenties. At 22mph the tone abruptly changed up. It did that again at 20, 17 and 12 (or 13). The sound cut out at single digit speeds (3 or 4 maybe?)

It sounded kind of like an automatic transmission downshifting.


I think I heard the sounds on acceleration, but deceleration was where it was pronounced.

Eco or D seemed to make little difference - it was all speed based



My best guess was I was somehow hearing the inverter changing switching rates.

I didn't think to try a coast down in neutral.


Any ideas? Anyone else hear strange thing in the cold?


(I can start my own thread if appropriate. )

 

[Computerizer]

I'm still noticing this in my car, again when leaving work when it's cold out (under 40). After thinking about it more I wonder if it's a sound coming from the fixed-gear "transmission" -- presumably there is some lubricant in there, and if it's cold outside and the car has been sitting, it may not be distributed very well and could lead to some mechanical sounds.

 

[DesertDenizen]

Thanks essaunders, your experience closely mirrors mine. Same conditions, same speeds, same sound. It has gotten milder here and I have not noticed it lately. Since it seems to correlate to temperatures, the Leaf tech's theory of ABS doing a diagnostic seems like flummery. The innate human tendency to feel compelled to come up with a theory, however farfetched, to explain an observation. I live by a motto I developed some time ago, Allow the Why to Die. We can ascertain the what, when, who and where, but the why is often an enigma.

 

[essaunders]

It happened again on the way home yesterday. Three battery temp bars, about 17f out. The sounds didn't seem quite as loud and the speed points seemed slightly different. But I did try a N coast - the sound is the same. Halfway home the battery temp went to 4 bars. I think the sound got fainter on the drive home too.

I did also note the sound seemed to stop at about 7mph.

The car seems to work just fine. I've got to go on for my 1 year battery check very soon. I might ask (but don't have high hope)

 

[garygid]

Are you hearing the Pedestrian Warning Sound, along with
the other sounds, when under 18 mph?

 

[essaunders]

Are you hearing the Pedestrian Warning Sound, along with
the other sounds, when under 18 mph?

No. I'm not mistaking the pedestrian sound or the high pitch normal leaf sound. This is a warble that is 'new'

 

[kubel]

I have a very eerie noise coming out of my car in eco mode when lifting off the accelerator from around 25 to 15MPH (not the pedestrian warning system) when it was in the single digits (3F). I grabbed my camcorder and recorded it (it was loud enough to cause concern), but I left my SD card at my desk at work, so I won't have a chance to upload them here until next week.

It's amazing how many noises this car makes in extreme cold conditions. The cabin rattles from the dash, the instrument cluster, the center stack, both front doors, etc... Going over bumps, the shocks squeek. And the high pitched whine that we hear around 40MPH? It's amplified. I was really worried the motor or gearbox would catastrophically fail with the noise it was making.

Yesterday I was unable to close the front charge port door, even though all the ice was cleared from it. And during our first snow, the charging handle froze to the car (took me a few minutes working at it to break it free).

 

[Rauv]

Yes, I, too get a grinding/whining sound at low speeds (not VSP) in the really cold weather. More when decelerating but not when braking. NOt sure what it is, but I'm assuming it is cold-related and part of ther regen system.

 

[09Bamb00]

Hi, here in Tampa the temps are in the low-mid 40's in the mornings. When I'm backing out of the garage I hearing a new humming. I have 5 battery temp bars. The humming stops after about 1 mile. I don't hear this humming in the evening when I'm leaving work even though I'm still at 5 battery temp bars. However the temp is usually in the high 50's and since I back into the parking space, I'm pulling out forward.
I also have discovered that annoying rattling of the dashboard in the morning and evening.