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I have 1997 Chevrolet Lumina sedan. I’m trying to diagnose a sound coming from my engine. It is a “whirring” noise that varies with the engine speed (e.g., if I accelerate, the sound becomes louder and the pitch increases a bit). The sound occurs constantly, but is best noticed during acceleration.

About 8 months ago, I heard similar noises and it turned out to be the alternator since the battery was draining and the voltage was below acceptable levels. Had that replaced and the sound went away.

I’ve opened the hood while the car is running, and the sound is definitely in the region of the alternator. However, I also know that an idler pulley with bad bearings can make a similar noise and so too can the power steering system. The power steering fluid is fine; I triple-checked that.

I haven’t noticed any faltering in the electrical system. The interior light doesn’t flicker or vary in brightness with acceleration, the air fan speed doesn’t vary in and out of acceleration, the console lights are fine, and there’s no battery or “Volts” indicator on the console. I’ve tried turning on all the accessories of the car — headlights with brights on, radio, holding the brakes, interior lights on — to see if an indicator would come on, and nothing.

The noise has only been around for a few hours and it’s only been day time so I haven’t been able to try the headlight trick effectively. Also, it is extremely cold: only about 5 degrees Fahrenheit.

Any thoughts on what it could be?

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  • Are you able to take individual component belts off to test, or is a single serpentine system?
    – Nick
    Feb 10, 2013 at 22:26
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    It could be the belt itself (the sound of it passing over the different pulleys). Could also be the water pump pulley or the A/C compressor pulley. It's not likely that it's the crank pulley (the one that drives all the others) or you'd have other problems. You can try the old trick of rubbing a bar of soap (plain old Dial or something similar) on the underside of the belt to see if that quiets anything down. If not, then it's probably a bearing in one of the pulleys. The best chance of figuring out which one is to take off the belt and check each one.
    – Cᴏʀʏ
    Mar 8, 2013 at 16:08

2 Answers 2

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First and foremost, great presentation, very descriptive. Looking at the belt diagram on the vehicle it seems that it is in dead one belt. Here is how I would handle this.

If you have the ability and tools:

  • Remove the serpentine belt and inspect all pulleys (not just the ones in question)
    • In order to remove the belt you will have to pull the spring-loaded tensioner away from the belt. Reference this photo
      • Be careful when you release the tensioner. When released it will bite you if you're not careful.
    • Spin the pulleys hand and see if you can get them to make noise.
      • The pulleys should not "spin forever". New pulleys have a slight resistance giving them a tight feel while old pulleys will make a "crackling" type sound from its center (where the bearing sits).
    • Grab the top and bottom of the pulley and see if it has any play. rocking it against it's center as if it were a see-saw.
      • The pulleys should show very little to no play in them. If they do show a decent amount of movement. It's time to replace them.

While the belt is off, be sure to check the belt and make sure that it's not getting chewed up by any of the pulleys or it's not cracking. - I only say this due to the fact that while it's off it's a good time to replace it if it's worn out.

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  • If it is in fact the alternator again, then unless you were told otherwise by the shop that installed the alternator, you have 12 months or 12k miles, whichever comes first, warranty on any repairs. Parts and Labor. If they told you otherwise it would also require your signature on the original estimate, approval, and final repair order stating that you were aware of waiving the warranty.
    – cinelli
    Mar 22, 2013 at 13:56
  • It actually turned out to be one of the pulleys (and thankfully not the alternator). The original pulleys were still on the vehicle-- had the noisy one replaced and all is quiet now.
    – kevin628
    May 24, 2013 at 16:55
  • Glad to hear it's all figured out.
    – cinelli
    May 29, 2013 at 8:44
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It can be your Alternator going bad, if you know how to use a voltmeter, while your Lumina is running, put the red lead of the voltmeter to the positive red cable on your battery. Then take the black lead on the voltmeter and place that one on the negative black cable on the battery, The voltage should be 13.8-15.0 volts, If it is 13.00 volts or if it is 15.01+ volts, your alternator is going bad. and you can try putting your blower motor on high, blasting the radio and putting your rear defroster on, if the voltage drops to like 12.00 volts, have your alternator changed.

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    What was the reason for the downvote? Sure, the answer can be improved, but is it factually incorrect? If so, elaborate.
    – theUg
    Mar 9, 2013 at 17:28

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