Humming in engine

[BlazerLT]

Originally Posted by Blkhrt51

No i dont use those, I live in az.

Does it go away when you use the AC?

[Blkhrt51]

no.

[BlazerLT]

any chance to get a sound clip of this?

[Blkhrt51]

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

[OverBoardProject]

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

[hcary]

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.

[riccbhard]

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.

[Blkhrt51]

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.

[OverBoardProject]

Originally Posted by Blkhrt51

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

[wolfox]

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.

Originally Posted by riccbhard

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.

[Blkhrt51]

Now its starting to get louder

[BlazerLT]

Originally Posted by Blkhrt51

Now its starting to get louder

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

[big_bell]

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.