Humming in engine

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?

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

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

Is it more of a whining noise?

or you could be hearing the fuel pump at idel

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.

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.

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.

Does it go away when you rev the engine?

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

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.

Need to know more about this hum.

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

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.

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

No i dont use those, I live in az.

No i dont use those, I live in az.

Does it go away when you use the AC?

no.

any chance to get a sound clip of this?

Maybe ill see what I can do. Have any ideas on what it is?

How about a small vaccum leak in the brake booster?
Although the motor would idle rough then

Try a mechanics stethoscope. Similar to a doctors stethescope, but with a foot long metal rod to touch the engine instead of that drum thing. Costs less than $10, and can be pretty fun to hear the different sounds from various parts of the engine.

Sounds like the good 'ol alternator. Our '98 LT 4.3 Vortec made the same noises (whirring, humming) before the alternator went bad. Some symtoms where; lights dimming and flicking at idle and when first starting it up and night, and then putting it in gear, drive forward about 5 feet and if you watched you'd see the lights flick on and off very very fast (maybe a 5th of a second).

Took the alternator to Advance to be tested and sure enough "bad diode pattern"

Like suggested above use a mechanic's stethescope to check all around that area.

The light thing was happening before the humming was. I think it might be the fuel pump due to it only happens when im at idle or not pressing the gas.

The light thing was happening before the humming was. I think it might be the fuel pump due to it only happens when im at idle or not pressing the gas.

Unless your truck is an 85 or older the fuel pump is electric and in the fuel tank. Not under the hood at all

Alot of vehicles do this - they test the ABS unit when you first roll and you are doing about 5~10 MPH. My mom thought that there was something wrong with her Minivan when this would always happen, but turned out, it was just the test loop the ABC module does at first start up. I wouldn't worry too much about this. It's when you're sitting idle at a light and volts are dropping below 12v or so that I worry. Had a brand new Isuzu Rodeo that did this, and then the alternator came apart like a grenade. The bearing seized up with "dramatic results" - dramatic enough to dent the engine hood out from the inside.

Sounds like the good 'ol alternator. Our '98 LT 4.3 Vortec made the same noises (whirring, humming) before the alternator went bad. Some symtoms where; lights dimming and flicking at idle and when first starting it up and night, and then putting it in gear, drive forward about 5 feet and if you watched you'd see the lights flick on and off very very fast (maybe a 5th of a second).

Took the alternator to Advance to be tested and sure enough "bad diode pattern"

Like suggested above use a mechanic's stethescope to check all around that area.

Now its starting to get louder

Now its starting to get louder

If it is that loud , you should be able to pin-point it.

I just had an alternator problem and it had a low huming sound. the best thing to do is to go down to your local autopart's store and get them to do a load test on your batt. and that could tell you if your alternator is bad or not.