Clattering from underneath

Nasco12

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Twickenham
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W202 C240 1999 Green; Previous: W202 C200
Here's what happens:

Start up - go to the supermarket - stop - return to car 15-20 mins later - start up - metallic clattering from underneath - move off - clattering ends.

This does not happen when starting from cold - only when the engine is warm. If I get out of the car to have a look it disappears.

Tonight as I was slowing down at the end of my journey I heard the same clattering. This is the first time it has happened when the car has been in motion.

Any ideas?
 

BlackC55

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Loose exhaust bracket?

Broken exhaust mount?

Loose CAT?
 

whitenemesis

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Parking brake cable loose? Or is that only the 203?
 

whitenemesis

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:doh: :eek:
 

A-AvantGarde

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Sounds like it could be a broken Catalyst or exhaust mountings...
 

Rorcus

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Mar 9, 2011
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2001, E320 CDI
:) yep definitely sounds like a piece of the honeycomb in the cat has broken away.. Once warm the cat expands enough to give it more room to rattle, then often when moving off it can slide/move back and wedge causing the sound to stop and can then come back as you decelerate as it moves free again.

Youtube search "Cat rattle" and you should find an example that probably sounds just like yours. :D
 

whitenemesis

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I believe some have 'cured' this by slightly crushing the casing to hold the honeycomb.
 

Rorcus

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Cat rattle? Sounds expensive.

Not too bad.. (if it is the cat.) New Downpipe with cat can be got for around £100 and then bung a friendly Exhaust Centre £30-40 to fit it (Grays Tyre & Exh Cent on Heath Road Twick are pretty good, I took my Shogun there with a complete system in the boot inc cat and D/Pipes and he fitted the lot up for £70)..
 
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pc-uk007

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Aug 13, 2009
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LONDON
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2001, W220, S320L, petrol,
I had this problem last winter, metalic rattle at times stationary and if i had window open sometimes as i pull away from stand still any other times no noise heard,(no engine light illuminated) it will get worse when it does just take it to exhaust centre for inspection. mine was the cats at 90,000 miles.
 

mirras

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Jun 23, 2006
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Ayrshire
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Range Rover TDV8
My car developed a rattle from underneath a few weeks ago... turned out to be a heat shield that 'fell off'... £1.95 worth of penny washers and it was back on as good as new.... fingers crossed that's all it is for you, wiggle a few bits when the car is cold to see if you can recreate the noise.
 
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Nasco12

Nasco12

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Location
Twickenham
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W202 C240 1999 Green; Previous: W202 C200
Turned out it was either a loose heatshield or an exhaust bracket that had become detached from the exhaust pipe.

Jack at PCS sorted out both. Many thanks.
 

mirras

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Always good when a worrying problem turns out to be an easy fix :bannana:
 

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