Technical Strange Noise

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Technical Strange Noise

zutanoz

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Joined
Nov 7, 2005
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Devon
Hi

The noise is most noticed when going down a hill and not accelerating.

At just below 3000rpm and any gear there is a metallic rattling sound.

If you accelerate when it does it, it stops.

Can be heard in any gear, and most notable when going down hill as not accelerating, also can be heard when changing gear at around the 3000 rpm stage as also not accelerating during the change.

Any ideas what it could be?
 
Hi,
Have a look at the metal cover that covers the exhaust down pipes from the engine block (front of engine), this may have a split where the nuts hold it in place causing it to rattle at certain rpm. Replacements are available if this is the case or a temporary repair by using a large washer to cover the split or remove the cover plate. Hope it is as simple as this.
Goodluck
Steve D
 
Yep, sounds like a rattling heat shield. Presumably it doesn't rattle while you're accelerating because putting down the power makes the engine rock slightly on its mountings, and thereby moves whatever's vibrating further away from whatever it's vibrating against.
 
Last edited:
I changed the heat shield that covers the exhaust manifold recently, well the garage did. So don't think it's that as it did it with the old one.
 
I concur with the others and have had this issue myself. Even if the heat shield is fairly new, they're very thin and it may still resonate under certain conditions. Try bending it very slightly and see if this alters/stops the frequency of the rattle! Once you eliminate the heat shield try checking the catalytic converter. The ceramic fins inside can break up and leave tiny pieces like broken crockery inside. Get under the car and thump the exhaust with your hand. The rattle is almost certainly on the outside of the engine but little niggles like these can take a while to locate. The other thing is, because you know you can induce the rattle, you tend to! Have fun! Steve
 
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