High pitched noise from engine compartment

[Tony]

Hi,

The whining noise comes when driving. It is present at idle after running for a while and is also consistent with how high i’m reving the engine. Sometimes it stop when i have been driving for a while, but not always.
Where should I start to looking for the cause? Any ideas?

Here is the link to the video where you can hear the noise: LinkToVideo

Topic

[Kasra]

In my experience high pitch whine can be bad pullies, old serpentine belt, or air leak. Any particular area it is coming from within the compartment? Also look at the belt and see if it is cracking and just give the belt pullys a little wiggle. However, a lot is going on down there so try to single out the area. What is the make and model?

[Tony]

Alternator belt looks somewhat worn and craked, I cant be sure which area the noise is coming from. Have to listen more carefully. Car is Rover 420 petrol ’98 pretty much honda civic/bmw 3 based.

[Mike]

does it only happen when you start the engine, and goes away when engine is warm.

If it is then it probably belt too tight or loose, tensioner, or pulley.

[george gonzalez]

It’s probably a dry bearing in a part that is spinning quite quickly, most likely the alternator or water pump or one of the other small idler wheels on that belt. You can often narrow this down by taking a long screwdriver and putting the business end on the non-moving part of the device and putting your ear to the top of the screwdriver. Sometimes this is inconclusive and you have to take off the belt and spin the pulleys by hand and see which one (or more) of them does not spin easily and without roughness.

[EricTheCarGuy]

An easy way to help eliminate components in a case like this is to remove the belts one at a time and then recheck for the noise by running the engine. If the noise goes away after you remove a certain belt, you know where to start looking. More information on issues like this, including a video on belts and pulleys, can be found here.

http://www.ericthecarguy.com/faq/diagnosing-noises-in-your-car

[Tony]

Thanks to all you guys! I found the noise and fixed it!

It was faulty alternator and I replaced it. Now the noise is gone and car works much better now! Amazing how much cars behaving improved just changing alternator, even my problems with high revs has gone… It was really in the end of its road 🙂

[Author]

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