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My wife's MX5 (mk1) is emitting a buzzing/vibrating noise from the exhaust (we think) at certain revs. Now, it's mounted (hung) from rubber straps, so I don't think it's something wrong with the fitting. We're thinking that perhaps the baffles are loose in the silencer. I popped into Kwik-Fit to see what they think/charge for a replacement and they guy in there said that it (loose baffles) was an MOT failure. Now I've had a company car for a few years, so I'm not too sure about this. Can anyone confirm this for me?
Also, if it is loose baffles(not sure how I could confirm that), is a replacement the only way? They, Kwik-Fit, are charging £157 inc fitting and VAT. Anyone know where we could get something cheaper? I have STFW , but not seen anything yet.
Not good news I know, but I have heard exhausts rattle in the manner you describe if the catalyst is breaking up - basically the cat honeycomb structure gets slightly samller as it rattles and is no longer a tight fit in the pipe - thus vibrates at certain revs - usually on trailing throttle/overrun.
just remembered the time honoured fix for loose things in the exhaust is to make then tight again by reshaping the exhaust to make the loose bit tight again.
What i'm trying to say is....whack it with the biggest hammer you can find and see if it stops or changes it - you may not have anything to lose if you're having to change it anyway - it may save you the cost & bother.
The silencer thing on my Blitz NURspec rattles at low revs & i've just got sum bandage type stuff which can take temps 2 650c so i'm hoping i will b able to wrap that around the silencer b4 screwing it in & it will prevent the silencer rattling against the backbox. Dunno if that's similar 2 wot yer askin but i'm only doing it since it sounds cheap & if i dont have silencer then neighbours r guna lynch me
it should pass providing it is not blowing excessivly it is in it's mountings of which none are broken and it passes the emissions test and it's not hitting the bodywork then loose baffles will not matter, you would have to be a really mean tester to fail it on that. i wouldn't
Had some more replies from mx5mods.com and they are saying it's most likely a loose heatshield :
The noise will be from a loose heatshield! Almost every '5 has had this problem if its over a few years old.
I would tend to agree with Glynn on this one... It's most liekly to be a heatshield and I reckon it is probably the one that goes above the small centre expansion box. Two large jubilee clips and a bit of scrawming under the car should fix it. Mine's done the same, mostly around the 2000-2500 rpm mark.
Fingers crossed!! Will have a look at the weekend.