99 Firebird with a whine

[Tom7227]

My kid has a 99 Firebird and there's a whine under the hood. I sounds like a bearing in the alternator but I'm not sure. She also got a check engine lite.

Could the alternator trigger the check engine lite?

Car has 135K on it. What happens in the the bearing goes? My guess was that she'd have a few miles before the battery died and the car stopped. Cash is tight and she'd like to push her luck but I'm not sure what the odds are.

Can you help?

[Whoaru99]

If it's a single serpentine belt, and the alternator bearing totally goes out, the belt could burn off or be thrown off.

If the belt burns off or is thrown off, the water pump stops and the power steering stops. Also, if the belt gets thrown off, there is a small chance of damage to radiator, etc.

Replacing or rebuilding the alternator is probably the cheaper alternative than a tow or worse (think panic when the power steering goes out on an inexperience driver).

[Scott K]

If it makes the noise all the time, just pull the belt off and see if the noise goes away! If it does then it is something that the belt is hooked to, if it doesnt, then it is something else! Alt bearings dont go bad very often, usually the idler pulley, or belt tensioner is what goes bad. If it goes away when the belt is off, spin all the pulleys listen for noise, and feel for roughness.

Another thing you can do is pull the wiring off the alt, sometimes the alt it self will have an electrical whine, if it goes away then, then replace the alt.

[Jeremy airjer W]

3.8 0r 5.7 liter?

This might be a long shot but turn the A/C on and see if the noise changes. Otherwise whenever I run into these types of noises I also typically remove the belt to help narrow down the possibilities.

[Tom7227]

Thanks for the info. I guess the best thing is to do was the Wanderer suggests and take off the belt and see what happens. Can I run the car for a minute or so without the belt?

There's an idler arm just under the alternator and with your help I'm starting to think that's the culprit.

Thanks again.

Tom

[Scott K]

Yes a few minutes will be ok, but I wouldnt run it much more then that.

[lotsofish]

If it's the tensioner pulley, you can get just a new pulley for it. It can be a little tight to get off, but it's a simple swap (1 bolt) once you get it off. It's fairly cheap too.

After you take the belt off, spin each one of the pulleys and if you feel any left/right movement or "grinding" that is likely your problem.

Another thing you might want to keep in mind. The power steering pump on these GMs can be noisy. If the power steering fluid gets a little low it can really get a good whine going. Check the fluid level in the power steering reservoir before you replace anything.

[Shack]

When I diagnose a hum concern, first thing I do is use a mechanics stethoscope and try to pin point what spinning device is causing the noise. Beware though, the eng. Is running and things can get caught into the belt. Some seasoned techs (I do not advocate this), apply a pry bar to the alt., water pump, power steering pump, air pump, idler pulley or tentioner and listen to the end of the pry bar. This kind of acts like a stethoscope. If you can not find the hum this way, then next step would be to remove belt and use stethoscope to pin point others area’s like the trans bell housing and such.

Good luck..

[chickeywing]

135K? Ever replaced the alternator? GM units don't usually last much past 100. As was already discussed, remove the belt. You don't need to start it. You should be able to spin all pulleys by hand. If you find one that's not silky smooth, you've found it! Start with the tensioner.

TC

[Tom7227]

Thanks. I wish I had the stethoscope setup as that would make it a cinch. Can you get those at a parts store?

[SCUMFROG]

Harbor Fieght Tools sells them cheap. There is one off Robert St. in West St. Paul.