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My trailblazer makes a loud rattling noise that sounds like a dancing gear or a dancing belt hitting something/rubbing on something. It's coming from the very front of the valve cover, the truck runs fine and doesn't have any issues, it just makes a concerning noise.

Note: I'm running it with 10w-40 atm, and I have yet to change the oil filter. Should I try going back to 5w and changing my filter to see if that stops it?
 

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2004 chevy trailblazer_lt
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The first thing I would do is remove the serpentine belt and then start the engine to see if the noise is still present. If the noise is gone, then you need to check for a bad pulley or bearing in the AC compressor, alternator, power steering pump, serpentine belt tensioner, etc.

Remember, don't let the engine run too long so it does not overheat since the serpentine belt is off and the water pump is not pumping.

If the noise is still present then you know it is likley something internal.

Good Luck!
 
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The first thing I would do is remove the serpentine belt and then start the engine to see if the noise is still present. If the noise is gone, then you need to check for a bad pulley or bearing in the AC compressor, alternator, power steering pump, serpentine belt tensioner, etc.

Remember, don't let the engine run too long so it does not overheat since the serpentine belt is off and the water pump is not pumping.

If the noise is still present then you know it is likley something internal.

Good Luck!
That helped!
It’s the alternator. Loudest one I’ve ever heard.
I’m so happy I don’t have to replace my engine.
Thanks a bunch.
 

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You are quite welcome! My alternator made a racket too when the bearings went bad.
 
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