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Discussion Starter · #1 ·
My '55 is getting a rattling noise when under load, usually when accelerating with +50% throttle, above 3k RPM.

Noise seems to be coming from drivers-side of the engine bay (it's louder from the drivers seat) and the car does seem to have a slight vibration feeling through the pedals and through the seat.

Initially, after listening to it, my specialist thought it was "pinking" (ie, pre-detonation). I wasn't sure, so I swapped fuels (from 99RON, to another 99RON) but it made no difference.

It's been in again today, spent the day with it and ran it through diagnostics/STAR. He's spoken to Mercedes, and they're convinced it's not pinking, and it's actually movement/vibration, which he thinks is the exhaust, but they've checked and can't see anywhere where it could be the case.

Anyone have any ideas? I'm taking it to an exhaust place to ask them to give it a once over, but I'm not convinced it is the exhaust myself - I've had a loose exhaust heatsheild before and you can hear the noise below you, not from the engine bay (or apparently from the engine bay).

I might try another specialist, I don't particularly want to take it to the main dealer!
 

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Founding Member 2006
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is it a drone sound? is it between a certain rpm like 1200?
do you have a 3rd party exhaust like x pipe, etc
 

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2005 SLK55 AMG
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Could be one of the cats disintegrating ..
 

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Discussion Starter · #5 ·
Not a drone sound, a proper rattle, like something is loose. Car is completely standard.

Would a disintegrating cat make that sort of noise? Funnily enough, the garage did mention that removing the cats has solved this in the past, although I think he's just talking about general exhaust modifications fixing rattles when they're removed/reattached.

And pinking is still an issue (albeit rare) on modern cars with bad timing/fuel. Even the C63's had a pinking issue.
 

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Founding Member 2006
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cats would definitely produce a rattle

Catalytic Converter Rattling Noise

 

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Discussion Starter · #7 ·
Hmm. That sounds familiar, although it's more 'rapid' than that, but well worth investigating. Worry is that it's coming from the front and therefore maybe the primary cats :/

That being said, videos seem to suggest it makes the noise even when revving from idle - mine definately doesn't.
 

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tons of other 'cat' rattle videos on youtube :D
i would assume rattle would be different based on maker of cat, etc
 
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