Car making rough noise from engine, why?

2002 AUDI TT
120,000 MILES • 1.8L • 4 CYL • TURBO • 2WD • MANUAL
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WYLEYBUG
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My vehicle listed above started this morning with a red battery sign on the display and started making noise from the engine. Could a low/dead battery cause an engine mechanism to make noise even if the engine turned over and idled fine?
Mar 25, 2024 at 12:59 PM
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WYLEYBUG
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I should add the noise seems to subside when I revved it in neutral.
Mar 25, 2024 at 1:21 PM
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JACOBANDNICKOLAS
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Hi,

If the battery light was on, there could be an issue with a bearing in the alternator. Is it loud enough for you to record and upload for me to hear?

I attached a pic below showing the location of the alternator. See if that seems to be where the noise is coming from and let me know.

Joe
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Mar 25, 2024 at 8:50 PM
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WYLEYBUG
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Sorry, thought I did! And thanks, that’s the consensus me and my family have come to currently is that it is the alternator, as I tried to start the car later and it just doesn’t want to turn over, but the lights and electronics are working, making me think it’s the alternator. Good to know that isn’t a completely random guess!
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Mar 25, 2024 at 11:55 PM
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JACOBANDNICKOLAS
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Hi,

What I suggest is to remove the serpentine belt and inspect each of the belt driven pulleys. Check if any are difficult to turn or have excessive play in them.

Keep in mind, it could also be a belt tensioner or idler pulley that is causing tension to be lost on the belt.

Let me know what you find or if I can help in any way.

Take care,

Joe

See pic.
Mar 26, 2024 at 6:41 PM