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Chirping and squeaking mostly when the engine is warm

Tiny
JACK KCAJ
  • MEMBER
  • 2002 BMW 325I
  • 2.5L
  • 6 CYL
  • 2WD
  • MANUAL
  • 124,000 MILES
I have this strange noise when I let the gas go, from 2,000 RPMs to 1,000 RPMs, it only occures on this rpm range and mostly when the engine is warm, sometimes cold too. I cannot figure out what it could be. New DISA valve has been installed, I've sprayed belts and pulleys when the noise was present, and it didn't seem to change much. see video for sound.
https://streamable.com/8suh03
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Sunday, May 1st, 2022 AT 3:53 PM

17 Replies

Tiny
JACK KCAJ
  • MEMBER
  • 10 POSTS
Also, I forgot to add that it occurs in neutral and in gears, in deceleration phase.
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Sunday, May 1st, 2022 AT 3:56 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Thanks for the video. That sounds like a rattle.

Does it sound loudest in the engine bay or under the vehicle?

The first thing that comes to mind is a wrist pin knock/rattle. Basically, what happens is when the engine is under power the slop in the wrist pin of the piston is taken up and it doesn't rattle. Then when you are in deceleration the pin is able to move around and it causes a rattle.

So, the way that we need to check this is by starting with draining the oil and look for metal.

https://www.2carpros.com/articles/how-to-change-engine-oil-and-filter

Basically, if we have any metal at all then this is most likely from the cylinder walls and the piston is scrapping it as it moves around.

If there is no metal, then we can dig further based on all this info. So, let's start with this and go from there.

Thanks
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Monday, May 2nd, 2022 AT 4:39 PM
Tiny
JACK KCAJ
  • MEMBER
  • 10 POSTS
Thank you for the quick reply. When facing the engine bay, it comes from the top right so not really from the engine block itself (hopefully). Now that you say it I think its louder from underneath the car. I'm planning an oil change ASAP, also I try to check for exhaust leak as someone suggested it to me, what's your opinion on this? Thank you I'll update ASAP.
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Monday, May 2nd, 2022 AT 4:48 PM
Tiny
KASEKENNY
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  • 18,907 POSTS
It could be an exhaust leak but those normally don't happen just on deceleration. Normally when you get them to start leaking, they will tick when holding steady throttle. If it only happens on deceleration, then I would put my money on an engine noise.

Use a long screwdriver and touch it to different parts of the engine and get the noise to happen. Then put your ear to the end of the screwdriver and the noise will be transferred up to your ear.
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Monday, May 2nd, 2022 AT 4:57 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
Does it seem like the noise is coming from under the car? It sounds like you have a catalytic converter that has fallen apart, jack the car up this guide can help:

https://www.2carpros.com/articles/jack-up-and-lift-your-car-safely

Take a rubber mallet and gently strike the catalytic converter and mufflers to see if you can hear anything loose in there. If so, here is how to replace the catalytic converters in the diagrams below.

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Monday, May 2nd, 2022 AT 4:58 PM
Tiny
JACK KCAJ
  • MEMBER
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Yes, makes sense. I'll be able to do that this weekend as I need someone to rev it and also, I need to drive a little for the car to make the sound first. Thanks I'll update when I have news.
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Monday, May 2nd, 2022 AT 5:00 PM
Tiny
JACK KCAJ
  • MEMBER
  • 10 POSTS
Yes, Ken from under the car. I'll apply this procedure ASAP. Thanks
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Monday, May 2nd, 2022 AT 5:02 PM
Tiny
KEN L
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Sounds good. Please let us know.
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Monday, May 2nd, 2022 AT 6:21 PM
Tiny
JACK KCAJ
  • MEMBER
  • 10 POSTS
Okay, so, today I had some time to oil flush the engine, no metal shavings in the oil at all, the oil only had 4,000 kms but I was planning on changing it soon anyway because the car has been sitting a few years before becoming my property (prior to that the oil was 4 years old for 2,000 kms old).
Anyway, I tried to listen with a screwdriver mostly from the cover and the water pump, but it seemed normal to me (but I'm far from being an expert).
What I noticed better now is that the noise is coming from under the car. I made another video in my garage where the noise reverbs on the walls.

Unfortunately I could not do Ken's procedure today.
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Tuesday, May 3rd, 2022 AT 8:58 AM
Tiny
KEN L
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Thanks for he video, is there an aftermarket turbo on this car? If so, this can make the cats overheat and break apart.
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Tuesday, May 3rd, 2022 AT 11:54 AM
Tiny
JACK KCAJ
  • MEMBER
  • 10 POSTS
No turbo on this car, its stock excepted the rear muffler, I even removed the K&N air filter for an OEM.
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Tuesday, May 3rd, 2022 AT 12:10 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
It sounds like the cats have come apart and the particles are in your muffler, give the muffler a knock with a hammer to see if you can hear something inside.
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Tuesday, May 3rd, 2022 AT 4:15 PM
Tiny
JACK KCAJ
  • MEMBER
  • 10 POSTS
Okay, I will do that when I get home. I'll keep you updated. Thank you a lot.
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Tuesday, May 3rd, 2022 AT 10:15 PM
Tiny
JACK KCAJ
  • MEMBER
  • 10 POSTS
Okay, so, I cannot do that today, I'll be back Saturday to continue the inspection. I'd like to add that's its very limited to 2,000 to 1,000 RPMs, and as soon as I touch the gas, even 1% the noise goes away, also I don't have any loss of power. I don't know if that helps but it's there. Thank you, I recently discovered this website and I must say I'm amazed.
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Wednesday, May 4th, 2022 AT 10:53 PM
Tiny
KEN L
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Good to hear, we are helping whoever needs us. Please let us know what happens.
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Thursday, May 5th, 2022 AT 9:47 AM
Tiny
JACK KCAJ
  • MEMBER
  • 10 POSTS
Hello, so after some investigations it seems it could indeed be a leak around the exhaust manifold. I'll have to wait a few months to get it done because I don't have any room at home and unfortunately and I can't drive right now for reasons.
I'll come back to update this thread when the problem is fixed, that could help others hopefully.
I'd like to thank the amazing team on this website for giving me clues about the problem, I'm very thankful.
See you in a bit for the update.
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Wednesday, May 18th, 2022 AT 9:39 AM
Tiny
KEN L
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You are very welcome; we are here to help. Please let us know what happens.
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Wednesday, May 18th, 2022 AT 11:35 AM

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