Humming in engine

[Blkhrt51]

When I come to stop I hear a humming or something comeing from my engine, but when I start to accelerate it goes away. Any one know what might cause this?

[rlith]

Have you popped your hood to listen? One guess could be the clutch fan... (A guess)

[blazes9395]

....or a bad tensioner pully, idler pully, bad alternator bearings, you have to look and listen under the hood....

[BlazerLT]

Is it more of a whining noise?

[dmbrisket 51]

or you could be hearing the fuel pump at idel

[DonSor]

Without knowing what car it is it might be that when you accelerate you just don't hear the humming noise over the engine. As everyone else suggested pop the hood and see where the noise is coming from. Certainly not in the drive train if you're not moving. Try squirting water arount pulleys and see if there is any change. At this point I would venture to guess that one of your rotating accessories has bearings going bad. Ex: Alternator, A/C, Power Steering, fan clutch of course unless you have electric radiator fan, and maybe the water pump.

[Blkhrt51]

its a 97 lt. and when I pop the hood i cant really pin point to exact source of the sound, but it does go away when i accelerate.

[DonSor]

I presume you meant accelerate in speed while driving as opposed to just gunning the engine. As I suggested before try squirting water with a spray bottle at the pulleys. Borrow an engine stethoscope and start probing. Have someone change engine rpm while you listen. S-10 are rea wheel drives and they are not as bad to inspect as front wheel drive vehicles.

[BlazerLT]

Does it go away when you rev the engine?

[Blkhrt51]

yes it stops when i rev the engine. but when it starts to fall back to idle it starts again.

[DonSor]

The only things that I know of whereby something changes from rev up to idle are: A/C, water pump, fan clutch if equipped, power steering, and the alternator. I presume you had the A/C off. water pump problems don't hum, it'll be more like a squeal. Power steering noise will be noticeable when you turn your wheels, and alas! the alternator whick could be producing the AC hum called magnetostriction. Anyway you can take the alternator out of the circuit. Hard to do if you have serpentine belt. Might be worth the try.

[BlazerLT]

Need to know more about this hum.

Is it a high pitched whine or what exactly is it?

[Blkhrt51]

it is a low hum. I think it might be the alternator due to some electrical stuff that also is going on. The lights sometime dim and go back to normal, but this happnes only sometimes and not when the noise is made. Its really weird to try and describe a hum. It sounds like it has intervals in it ( if that makes any sence ) and is not that loud in the cab, but you can still hear it. When i pop the hood its a low cracking hum i guess.

[BlazerLT]

does it seen to happen more when you have the climate controls set to defrost?

[Blkhrt51]

No i dont use those, I live in az.