Exhaust noise help please

Archives of Posts to the NZ MX5 List back in 2004
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Ian Chapman

Exhaust noise help please

Post by Ian Chapman » Mon Nov 29, 2004 2:35 pm

Hi All

Our 1990 has a high frequency rattle/squeak which I'm confident is from
the exhaust.

This occurs at low-mid revs under load. It only last a second or so
usually in the lower revs as speed builds up. Doesn't occur when cold
but quite a bit when hot.

I suspect the exhaust hanger rubbers have gone a bit mushy and when
they get warm and therefore soft allow the exhaust to vibrate under load
and set up the resonance. I've tapped and banged the system and can't
get the noise. With my lovely assistant slowly and carefully engaging
the clutch with the brakes on so to bog the engine down close to stall
and me lying beside the car I can see the exhaust system vibrate and get
some of the noise.

I've been instructed to fix it as it's hard to be a cool in a squeaky
car.

Has anyone had an issue with exhaust rubber hangers going soft and
causing this on their MX5 or other steed?

Thoughts on whether new stiff rubber will help (I eagerly await the
Viagra suggestions)!

Other thoughts on what it might be?

Thanks

Ian

Graeme H

Exhaust noise help please

Post by Graeme H » Mon Nov 29, 2004 2:49 pm

Could be that the muffler is on the way out. try sitting stationary and gently ease your foot on the gas up through the revs. I had a similar problem recently, but it appears to have cured itself...I think most of the packing got blown out at yesterday's tarmac gymkhana (which was very good fun, I can tell you :0D )

Graeme H

[...]
Ian

http://miata.cardomain.com/id/britracinggreen

Ross Bryon

Exhaust noise help please

Post by Ross Bryon » Mon Nov 29, 2004 2:53 pm

Just fixed a similar buzz-like rattle which I was sure came from a
silencer baffle -- until I changed the silencer and it was still there!

It still sounded like it came from the rear end of the car, but I found
that that was just the effect of forward movement and the sound
"bouncing" off the tarmac.
The culprit was the small heat shield just below the main header heat
shield. A metal "fin" of this heat shield was hitting against either
another part of the shield itself or the exhaust pipe at a certain
engine resonance -- most audible upon deceleration.
In any case a small bend with the screwdriver "fixed" this annoying
sound which it has taken me months to "trace".

Hope yours turns out to be as simple.


Ross Bryon
1991 BRG V-Spec Roadster
Auckland

On 29 Nov 2004, at 2:35 PM, Ian Chapman wrote:

[...]

From akjellberg@kpmg.co.nz Fri Apr 27 18:34:26 2007
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Subject: Front brake noise
Date: Mon, 29 Nov 2004 15:21:32 +1300
Thread-Topic: Front brake noise
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Hi all
I have that annoying rattle in the front brakes. (Does not stop when I
apply the hand brake but does when I apply the foot brake.)

Is there supposed to be an auto adjuster to keep the pads against the
disk, like the back, if so and it has seised, is there and easy fix?

Adrian

David & Judy Kerr

Exhaust noise help please

Post by David & Judy Kerr » Mon Nov 29, 2004 9:12 pm

Hello Ian,

It may be a lot cheaper to have your wife's ears retrained not to hear the
noise...
I still have that muffler for you just waiting for a reply to my email on
when you will be home for me to drop it off.

Dave.

Greg

Exhaust noise help please

Post by Greg » Mon Nov 29, 2004 9:28 pm

Hi, Ian

I've got a very similar buzz / rattle on my 1990 ... only when warm & at a
couple of specific engine speeds going up through the rev range to about
2,700 rpm.

As it happens the car was in for a service with Glynn at City Garage today -
he & crew tried to find it & isolated it to the exhaust. Heat shields are
fine, as are hangers. He reckoned that it could be the cat converter ... in
which case it's a replacement job. Fine excuse for a system upgrade I
reckon !

Regards,
Greg
1990 V Special

Voodoo

Exhaust noise help please

Post by Voodoo » Tue Nov 30, 2004 11:33 am

Hi Ian,

You know I just may have a similar problem with my car. A couple of times
recently I've heard a high frequency shriek (sort of) as the car's revs
dropped. It sounded like a resonance in something metallic, and my guess has
been the exhaust system. I have after market extractors, cat, and muffler with
I recall all heatshields (apart from that under the boot) removed. I've
thumped the tailpipe and if done vertically I can generate some sort of
vibration sound but I haven't yet pursued it further.

I'll be very interested to know whet you find with yours.

Gary


On Mon, 29 Nov 2004 14:35:42 +1300, Ian Chapman wrote:

Hi All

Our 1990 has a high frequency rattle/squeak which I'm confident is from
the exhaust.

This occurs at low-mid revs under load. It only last a second or so
usually in the lower revs as speed builds up. Doesn't occur when cold
but quite a bit when hot.

I suspect the exhaust hanger rubbers have gone a bit mushy and when
they get warm and therefore soft allow the exhaust to vibrate under load
and set up the resonance. I've tapped and banged the system and can't
get the noise. With my lovely assistant slowly and carefully engaging
the clutch with the brakes on so to bog the engine down close to stall
and me lying beside the car I can see the exhaust system vibrate and get
some of the noise.

I've been instructed to fix it as it's hard to be a cool in a squeaky
car.

Has anyone had an issue with exhaust rubber hangers going soft and
causing this on their MX5 or other steed?

Thoughts on whether new stiff rubber will help (I eagerly await the
Viagra suggestions)!

Other thoughts on what it might be?

Thanks

Ian

From jifjif@gmail.com Fri Apr 27 18:34:39 2007
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Date: Tue, 30 Nov 2004 11:34:37 +1300
From: ~Jeff~ <jifjif@gmail.com>
To: MX5List <mx5list@mx5club.org.nz>
Subject: Re: identifying what you have
In-Reply-To: <20041129214813.XDSR27493.pop2-rme.xtra.co.nz@210.86.15.137>
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Anything '96 or after is OK for compliance as I understand it, so all
the NB models will be fine!

PS - get one of your "helpers" to get you a Road&Ster magazine, lotsa
goodies in there... <drool> .Option magazine is also good, but you'll
hardly see any MX5 stuff in there. Actually the OSIM (?) bookstore in
Commerce St, Auckland has Option magazine, but it's ~$35 !

Jeff


On Tue, 30 Nov 2004 10:48:13 +1300, fhinz@xtra.co.nz <fhinz@xtra.co.nz> wrote:
[...]

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