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01-11-2017, 01:06 AM | #1 |
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Can anyone identify this sound?
I have 08 e93 m3 at 69000 miles and I have been hearing weird metal rattling/chirping noise at around 2000~3000 rpms at acceleration.
Below is a video upload from another m3 owner having same issue. You can clearly hear it from 2 seconds ~ 8 seconds. I took my car to several independent BMW shops but they were unable to nail it down. So I took my car to Southbay BMW. At first, foreman went driving with me and his opinion was engine knocking. But I wanted to make sure what it is so left it for a full diagnose. And guess what? They kept my car for 13 days and concluded it was not engine knocking and it's just a normal sound from M3 and yes...I ended up paying $195 to the stealer for nothing. This sound happens at almost every gear now and is very annoying. And it's more distinguishable during summer and uphills. Can anyone identify this noise? Truly appreciate it. [/QUOTE] |
01-11-2017, 02:19 PM | #3 |
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These engines don't have rocker arms.
I hear a slight clinking like heat expansion, which would be normal. I think I also hear some pre-ignition type knock which would not be normal, and might be a bad coil (knock sensing system), or just bad/low grade fuel. |
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01-12-2017, 02:54 AM | #4 |
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Thanks for the input but the dealer confirmed it's not knocking. And I have been using Chevron 91 octane ever since I bought the car and it is the best gas we can find near where I live in southern california...
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01-12-2017, 09:15 AM | #5 |
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Is it DCT or 6MT?
What I hear in the video is a very deep rattle/knock. Not a light 'chirping' or 'tapping'. Since you say it's more prevalent when the engine is under load, it really sounds like the ignition timing is too far advanced, regardless of what the dealer told you (wouldn't trust them anyway since they also told you the sound is normal). If the DME isn't getting proper information from sensors then it won't time the ignition correctly. It is definitely not normal. Have you had an oil analysis performed after the sound has started become more pronounced? |
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01-12-2017, 12:52 PM | #6 | |
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01-12-2017, 01:03 PM | #7 |
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I ask about an oil analysis because having one done may be able to rule out rod bearings as the noise source. It doesn't immediately strike me as RB noise on my speakers, but noises always sound different in person.
This engine doesn't have a knock sensor per se. Knock control is built into each coil through ionic sensing and relays data to the DME to control ignition timing. A bad coil or harness could cause problems here, even if the cylinder still fires. I have found that the 6MT clutch or flywheel can make strange, hard to diagnose noises. I just posted another thread where a clutch failed and burned the car up. I don't think you're at risk of that but a broken spring strap(s) could cause some noise and should be inspected along with the flywheel (which is a dual mass design). Unfortunately its a tranny-out job, but your mileage is getting high enough that it would be prudent if only as a preventative measure (I have seen them failed at 47k miles). |
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01-12-2017, 01:20 PM | #8 | |
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I had the exact same issue. Engine bed plate needed to be retorqued -- my dealer (Brian Jessel BMW) has seen it happen a few times. I'll see if I can dig up my service order and post a photo of it.. Example of the sounds mine was making: |
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01-12-2017, 02:19 PM | #9 | |
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OP, I think you have your culprit. |
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01-12-2017, 04:18 PM | #10 |
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Well bud, I think you're going to have to post a decent video of your actual car. We could spend a year of back and forth taking guesses based off of other peoples videos.
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01-12-2017, 04:18 PM | #11 | |
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01-12-2017, 04:21 PM | #12 |
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01-12-2017, 06:07 PM | #13 | ||
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01-12-2017, 06:40 PM | #14 | |
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01-12-2017, 07:02 PM | #15 | ||
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01-12-2017, 07:39 PM | #17 |
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There is never slack in the chain, regardless of wear. Slack would introduce variances in cam timing. It could wear all the way through the guide but the oil pressurized piston in each of the two tensioners will continue to extend to take up any slack.
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01-13-2017, 02:25 AM | #19 |
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01-13-2017, 02:34 AM | #20 |
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01-13-2017, 09:27 AM | #21 |
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I've done them, replacing the two tensioners isn't hard. It can be done in less than an hour and you don't even need to raise the car. The chain rails inside the engine don't really wear down. If your tensioners have somehow failed and introducing noise, it would sound different than what is depicted in the posted video. A failed tensioner will cause more start up rattle which subsides once they receive oil pressure, not usually as random noise and rattles as depicted in the video.
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01-13-2017, 12:14 PM | #22 | |
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