Help diagnosing rattle on start up- Video

[mi1rmac]

Hey All,

Trying to chase down a rattle that only occurs on star up sometimes sounds like it coming from the middle of the vehicle not the engine. Car is completely stock.

Any suggestions what it is?

https://www.flickr.com/gp/44704288@N06/3M377A

[Sukks2bu]

Maybe downpipe or baby redonators

- - - Updated - - -

Maybe downpipe or baby resonators

[Teamnct4]

Has been happening on my 2015 since I bought it new. Doesn’t seem to be anything harmful from what I’ve read. Happened with my stock exhaust and with my AWE.

[doughboy17]

It is common and I've heard several speculations re: what it is, but there seems to be no consensus.

[ABanT]

Bumping this old thread as I have the same noise. Anyone else have this or knows what it’s coming from?

Thanks


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[BEight SFour]

You guys check your cats? Flex pipe?

On the E36 forums i use to go on the main cause of that rattle on start ups would have been those. Even if you think it's still good theres probably a crack some where.

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[mi1rmac]

FWIW I have now replaced my exhaust with AWE resonated downpipes and a touring catback. Noise still persists.

Even watching exhaust videos online numerous car have this same vibration. Crazy to think no one has figured out what it is.

[gfro1234]

Does it sound like this: https://www.audizine.com/forum/showthread.php/660249-15-Engine-rattling-noises-at-cold-start-V6-3-0-TFSI?

If so could be your cam chain tensioner

[ABanT]

Not the chain tensioner. I have that as well and this is different. It’s more from the middle to rear of the car.


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[ABanT]

You know what, maybe it is the chain tensioner. I don’t hear that secondary rattle if I don’t get the chain rattle.


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[mi1rmac]

You know what, maybe it is the chain tensioner. I don’t hear that secondary rattle if I don’t get the chain rattle.


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The noise begins roughly 1-2 seconds after the car starts and isn’t coming from the engine bay, additionally it happens regardless of cold start vs warm engine.

My understanding is chain tensioner noises are immediate upon startup and mainly happen during cold starts. Given this I think this rattle is different, but honestly who knows.

[ABanT]

I also didn't think it was related to the chain tensioner at first.

I started my car a total of 10 times today in two sessions, 2 cold in succession and then 3 warm. I got the secondary rattle on the cold starts and none on the warm.
Did it again later in the day and it was the same thing. No chain rattle, no secondary rattle from the mid/rear of the car.

Maybe the chain rattle is echoing so that it sounds like its coming from the rear? When the oil pressure builds something rattles. Sounds like a robot having a spasm.

[Bartlett]

It might be related to your OEM flex pipe. Is it worn?