Low pitch hum

[jasonharrison]

I am completely stumped as to what this noise is or the whereabouts of its location. I will try my absolute best to describe it and am planning on getting a recording of it tomorrow.

I have an Auto TD5.

It's a low pitch hum made of 2 notes with the first note in a much higher pitch than the second lasting about 4-6 seconds and presents itself quite frequently. The sound appears to be coming from the drivers side of the car possibly in the dash or behind the firewall. It's only present with the engine on and can be heard both stopped in gear and moving at low speeds (both low and high gear). The noise is not affected by speed either.

Weirdly enough I can stop the noise by moving the gear selector into Park.

I've tried disconnecting the battery hoping that would reset something but that didn't work.

I'm hoping someone out there can help explain this noise.

[northiam]

Could be this

http://www.aulro.com/afvb/discovery-2/126616-disco-2-getting-rid-whirring-noise-alongside-steering-column.html

[rob tilbury]

I would be putting money on that little fan in the link above ,,,
I believe its to do with the air temp in the cabin ??
mine squeaks so i just wd40`d until i get time to rip it out and clean it

[jasonharrison]

Definitely more of a hum than a whirring sound. I've just cleaned the little fan and the hum is still present.

It's like seeing a ghost, you'll believe it when you see/hear it. Will be trying to record it today.

[discorevy]

Does it have ACE.?

[jasonharrison]

It does have ACE

[discorevy]

Check you don't have any rocks / stones between the pipes / chassis , they can give a low frequency hum usually noticeable at lower revs but if it has just recently become more noticeable then rocks / bent pipes etc are what to look for.

[jasonharrison]

I've had a thorough crawl underneath checking every nook and cranny but couldn't find anything where it shouldn't be (other than the standard oil leak)

It seems to be more frequent once traction control has been triggered from some off-roading.

[bob10]

Could it possibly be a gear noise from the transfer case ? If you go to low range, does the sound change?Try it and see.

[bob10]

I've had a thorough crawl underneath checking every nook and cranny but couldn't find anything where it shouldn't be (other than the standard oil leak)

It seems to be more frequent once traction control has been triggered from some off-roading.

Traction control makes a humming sound, when it kicks in. With my D2, it can kick in even on the tar, if I go over uneven ground, and lift a wheel. I don't know if that is supposed to happen or not. Worth thinking about when it happens for you.

[jasonharrison]

Could it possibly be a gear noise from the transfer case ? If you go to low range, does the sound change?Try it and see.
I don't think it's the gears as I can be stationary and still have the noise. Although the noise can only be heard if it's in gear. If I can hear it and I put it into Park it seems to stop the noise.