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Unidentifiable exhaust noise

My 147 has a very annoying noise which can be triggered by certain throttle pressures.

It has a metalic rattle that sounds like a broken Cat and seems to coincide with my ECSF light coming on. The noise is only really noticable after about 10 miles and seems to get worse from then on.

This may have something to do with the exhaust elements reaching a certain temperature. I can re-create the noise by driving the car at the lowest speed range for each gear and then giving it some throttle, i.e 20mph in 3rd, 30mph in 4th and 40mph in 5th. The sound is much stronger when driving up a hill and if I hold the trottle position I can also hold the rattling noise. Once i reach higher revs the noise goes away.

I have taken but Cats off the car to look down inside. Both seem fine and don't seem to have broken up. I have recently had my ARB changed and asked the mechanic to inspect the exhaust system for anything to make this noise. Nothing seems to be out of the usual and the heat shields etc are all tight.

Does anyone have any ideas as to what the problem could be?

I still think that it is that Cat but don't know if this would trigger the ECSF light.

Cheers guys
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Re: Unidentifiable exhaust noise

Yes, I do.
I had this rattle from the exhaust drove me nuts trying to find out what it was, checked every nut & bolt, heat shields, the lot. Then I found the rattle. It was the flexible joint, I took this section of exhaust off looked down the flexy end and saw excess flexy pipe sitting against the outer pipe, it was this that was giving a metalic rattle, I distorted the excess flexy slightly inside the pipe, re-fitted and now its as quiet as a mouse! Hope this helps you.
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Re: Unidentifiable exhaust noise

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Originally Posted by Philski View Post
Yes, I do.
I had this rattle from the exhaust drove me nuts trying to find out what it was, checked every nut & bolt, heat shields, the lot. Then I found the rattle. It was the flexible joint, I took this section of exhaust off looked down the flexy end and saw excess flexy pipe sitting against the outer pipe, it was this that was giving a metalic rattle, I distorted the excess flexy slightly inside the pipe, re-fitted and now its as quiet as a mouse! Hope this helps you.
That has happened a few times now.
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Re: Unidentifiable exhaust noise

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Originally Posted by Smaky View Post
That has happened a few times now.
To you, or its a common fault?
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Re: Unidentifiable exhaust noise

Poor quality manufacturing ... especially after-market parts
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Re: Unidentifiable exhaust noise

if the cat has broken up inside it could cause the ECSF light as the reading on the rear lambda sensor could be wrong.

Get the car to a specialist and get it looked at.

The cat on my 147 had broken up after 5 years!
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Re: Unidentifiable exhaust noise

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Originally Posted by Philski View Post
To you, or its a common fault?
There seems to be a whole batch out there fitted to '01 - '53 plate cars at the factory and the rattle is just a little deeper than normal heatshield noise, it can be a lot louder on over-run too.
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Re: Unidentifiable exhaust noise

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Originally Posted by gazza82 View Post
Poor quality manufacturing ... especially after-market parts
I agree, dealer fitted another gen part, it gave the same rattle thats why I sorted it, no point getting another fitted, you think they would do something about it.

Last edited by Philski; 09-03-10 at 12:55.
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Re: Unidentifiable exhaust noise

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Originally Posted by OperationAlfa View Post
if the cat has broken up inside it could cause the ECSF light as the reading on the rear lambda sensor could be wrong.

Get the car to a specialist and get it looked at.

The cat on my 147 had broken up after 5 years!
This is an option though, as when you look inside all you see is "the grid", this being the case means that you can't see the state of the internals properly, but you can (bolts willing) remove the cat and check to see if it rattles.
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Re: Unidentifiable exhaust noise

Oh yes, those bolts seize up quite easily.
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Re: Unidentifiable exhaust noise

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Originally Posted by Smaky View Post
There seems to be a whole batch out there fitted to '01 - '53 plate cars at the factory and the rattle is just a little deeper than normal heatshield noise, it can be a lot louder on over-run too.
Blimey, mines an 07 plate.
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Re: Unidentifiable exhaust noise

Got exactly the same issue on mine, the day i got the exhaust manifold gasket replaced. I was gonna do a post and ask but didnt know where to start explaining it. So thank you for that chaps for saving me the time. I dont think i could have heard it above the panting from manifold so therefore didnt notice.

Im gonna print this bugger out and take it straight down!
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Re: Unidentifiable exhaust noise

Wow... didn't expect such a quick a helpful response.

It would be great to know if it is the flexi causing this noise.
I just have three questions.

1. If it is the flexi joint could it only make a noise once the car has covered 10 miles or so? I fine mine quite when I start my journey in the morning and on some short trips. After a while of driving the noise then becomes noticeable and seems to get progressively worse.

2. Can it be inconsistent? I have had the car for about 7 months now and experienced this noise about 5 months ago. It then when away and has only come back in about the last month or so. Although it is much worse now and more regular.

3. Is it in any way connected to the MCSF light coming on? I know it shouldn't effect this but it doe's seem to coincide with the light being triggered. My mechanic has told me that I have a slightly faulty air flow meter which would cause this so it could just be a coincidence.
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Quote:
Originally Posted by Iorma20 View Post
Wow... didn't expect such a quick a helpful response.

It would be great to know if it is the flexi causing this noise.
I just have three questions.

1. If it is the flexi joint could it only make a noise once the car has covered 10 miles or so? I fine mine quite when I start my journey in the morning and on some short trips. After a while of driving the noise then becomes noticeable and seems to get progressively worse.

2. Can it be inconsistent? I have had the car for about 7 months now and experienced this noise about 5 months ago. It then when away and has only come back in about the last month or so. Although it is much worse now and more regular.

3. Is it in any way connected to the MCSF light coming on? I know it shouldn't effect this but it doe's seem to coincide with the light being triggered. My mechanic has told me that I have a slightly faulty air flow meter which would cause this so it could just be a coincidence.
I cant comment on 3.
The rattle was not evident until the exhaust would get hot and then it would only do it a certain revs, so if I was pottering around it would be very evident, sounded awful with the window down. Definately heat sensative. Its not the flexible joint that rattles, its the excess mesh inside touching the inside of the outer pipe, if you take this short piece of exhaust off (its real easy) and look down the flexy end you will see what looks like another ring, this is the end of the mesh, waggle the exhaust and you will see it move side to side and you will see it touching the walls of the outer pipe, this is whats causing the metalic rattle. Hope you can grasp my explanation. Its a quick job to fix.
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Re: Unidentifiable exhaust noise

As a quick fix to see if this is what is causing the noise I have thought about fastening two jubilee around the flexi-pipe and tightening them up to hopefully stop the excess flexi rumbing against the sides.

Do you think this would work?
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Re: Unidentifiable exhaust noise

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Originally Posted by Iorma20 View Post
As a quick fix to see if this is what is causing the noise I have thought about fastening two jubilee around the flexi-pipe and tightening them up to hopefully stop the excess flexi rumbing against the sides.

Do you think this would work?
I dont think so, if you are going to get under the car to put the clips on you might as well drop this section of exhaust off, it only takes 2 mins.
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Re: Unidentifiable exhaust noise

Hi all

I have finally found out that the noise I am experiencing is actually the engine pinking which is not what I really wanted.

I'm fitting a new knock sensor next weekend to see if this cures the problem...

Any thoughts?
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Re: Unidentifiable exhaust noise

New Knock sensor on and the noise is still there.
Does anyone think it could be the MAF?
Or what about the exhaust manifold bracket (is this different to the heat shield)
My mechanic thinks that it could be carbon build up in the cyclinders but there is no way I'm paying to get that sorted.

Does a broken variator only create a sound on start up. If so I can rule this out as mind runs normal when it idles.
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Re: Unidentifiable exhaust noise

Just an update.

I disconnected the MAF yesterday and the pinking stopped.
Today I refitted a new MAF and my ECSF light has instantly gone and the car is no longer pinking.

Love it when things work out like that!
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Quote:
Originally Posted by Philski View Post
Yes, I do.
I had this rattle from the exhaust drove me nuts trying to find out what it was, checked every nut & bolt, heat shields, the lot. Then I found the rattle. It was the flexible joint, I took this section of exhaust off looked down the flexy end and saw excess flexy pipe sitting against the outer pipe, it was this that was giving a metalic rattle, I distorted the excess flexy slightly inside the pipe, re-fitted and now its as quiet as a mouse! Hope this helps you.


I have the same problem with a metalic rattle, it sounds to be that its coming from the backbox though, saying that. I've fitted 3 different backboxes - all different factors too! I think I'm going to take the flexi off and take a look. I'm completly fed up of taking this exhaust apart!!! But more fed up of the noise!! :S
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