12-20-2020, 03:50 PM | #1 |
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Metallic sounding "rattle" at startup
When I start up in the morning for the first time, I get a very quick metallic rattle or vibration sound. It sounds like it's coming from the rear of the car, maybe the exhaust? I've shaken it and everything seems to be tight, nothing loose or squeaking. Any ideas? 2015 X3 35i, 67k miles
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12-20-2020, 04:50 PM | #3 |
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Probably the exhaust bracket would be my guess as well
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12-20-2020, 08:07 PM | #5 |
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Noise is still there. Checked brackets and hangers and all is tight and secure.
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12-20-2020, 08:22 PM | #6 |
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12-20-2020, 10:31 PM | #7 |
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Now that you mentioned it, I have done it but it never made that sound until recently, that's why I didn't associate it with the mod. I can reconnect things tomorrow and see if the rattle is still there or not.
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12-21-2020, 01:24 AM | #8 |
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Drives: 08 135i M Sport 6MT, 15 X3 35i
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It's probably just the exhaust flap in the tail pipe vibrating. It closes on cold start (stays open under no vacuum) and opens in certain conditions based around RPM.
It's probably rattling because the metal is cold and there's some extra tolerance because it has to operate with a fully heated up exhaust. If you only hear it on a cold startup and not an at-temp startup then it points to this as one cause.
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12-26-2023, 01:52 PM | #9 |
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Wouldn’t there be any issue if we disconnect the electrical supply to the actuator which control open/close function of the valve located inside the exhaust pipe? I believe this sub system is made for purpose and if we disturb them.. may get into other issue? Living with annoying noise is better as compared to expensive repair coming from other end if any.
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01-18-2024, 12:16 AM | #10 |
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Also dont overlook a couple things, the emergency brake cable that runs along the uderbody has has a set of cable harness/supports that can rattle against the heat shields. My 35i starts up cold and grumpy but then settles down, the added vibration from being cold and grumpy could be causing enough vibration to rattle those items mentioned. I would pay attention to the sound and then try to mimmick it by tapping the heat shields and see if there is any similarities, that will help you narrow it down. Also another rattle I discovered on my vehicle that is common is with the brake disc heat shields, they are round and bend easy, alot of people have reported pebbles, rocks getting lodged between the shield and rotors and rattling, my front left shiled was bent and rubbing aginst the back of the wheel rotor while it was spinning so I reshaped it back and it solved my problem, although you are hearing this while the car is not in motion so thats not going to be it, but I would investigate the possibility of a pebble lodged behind the shield and any other loose part tapping the various heat shields on the underbody.
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