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MG MGF Technical - Exhaust rattle

Hi
Can anyone help. I appear to have developed a rattle within the exhaust system. When the engine is cold there is no rattle at all, but once the car has warmed up and the exhaust is hot and the car is ticking over it rattles. I have gone under the back and the rattle in the exhaust seems to Come from around the CAT. When I rev the car the rattle seems to go. Has anyone got any ideas what it cound be.
M Carr

If it's like mine, it's the baffles in the silencer coming loose. Give the silencer box a good thump and you should be able to tell where the noise is coming from.
My nice new MGOC Supersports 'silencer' is on it's way, so it'll be bye-bye to rattles ;-)
Mike Cunningham

I have given the Silencer box a good thump but there is not rattle coming from there. Is there anything in the Cat that can rattle.

M Carr

If it's not the external heatshield, you're probably looking at internal failure. If you need a new one, look at this, it's much cheaper than your local MG-Rover spares outlet http://cgi.ebay.co.uk/MG-ROVER-MGF-1-8-91-00-Exhaust-Cat-Catalyst-Convertor-/290411410690?cmd=ViewItem&pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item439dde7502 - I just got one and it looks fine.
Mike Cunningham

Thanks for that I will get one from there.

If you dont mind me asking where didi your silencer from and how much was it.Because I was thinking if I am going to change the cat I might as well do the rest.
M Carr

MG Owners Club - http://www.mgocspares.co.uk/acatalog/MGOC_Spares_SYSTEM__MGF_TF__464.html - seems as good a price as any, and they seem to be well reviewed. You can even choose to be discreet or extrovert!
Mike Cunningham

The core of the cat can become loose causing a rattle like you have described, it happened to my son's MGF. We had to remove the cat and give it a shake to confirm, not a difficult job.
Eric Martin

Removing the cat on salt-caked UK cars can be quite, er, 'entertaining' - and often the studs will shear off. Ideally you need a blow-torch to heat the stud nuts to cherry red colour, thereafter things are easier.

Might be just as easy to take it to a friendly exhaust centre, where they'll have the necessary equipment...
Rob Bell

I'd got a set of Mike Satur's stainless nuts on the system, but having been undisturbed for a number of years they were seized onto the studs, so had to be sacrificed. You can get A2 stainless M10 nuts & bolts from Screwfix - http://www.screwfix.com/prods/48108/Bolts/Nuts/Hex-Nuts-A4-Stainless-Steel-M10-Pack-of-100 £14.63 for 100 nuts (rather a lot for one job, so I stuck with plated nuts - perhaps MGOC ought to stock them?) and http://www.screwfix.com/prods/23556/Bolts/Set-Screws/A2-Set-Screws-M10-x-40 £3.71 for 10 bolts. Add a bit of Copaslip and they might undo more easily in the future.
Mike Cunningham

you can say that again Rob.

I dont think the Exhust or cat has ever been changed the bolds on the cat are so rusted they will need to be cut out.
The rest of the exhaust is in Great nick so I only want to change the cat. I can see this being a whole system.LOL
M Carr

A word of warning - I've just fitted my new MGOC Supersports silencer to go with the new cat, and found that where the old silencer went on pretty much OK, no struggle, the new one finished up sitting 30mm offset to the nearside. I couldn't see an obvious difference between old and new boxes, but with everything done up the silencer was sitting that much offset. I was able to get the 30mm taken out of the cat by a local firm by cutting and trimming the inlet end. There was a visible slight angle between inlet and outlet, so I made sure that was preserved. Got it back and everything went together a treat, with the box sitting dead right.
Sounds OK too, albeit quieter than the old one, but then its innards were sliding about and rattling, so it was probably noisier than it was new. I'm not sure what effect the 4-2-1 manifold and its short flexi section have, but evidently with all the different parts of the system coming from different sources there is more chance of them not lining up correctly.

Mike Cunningham

Had it confirmed by British Legends in Southend last night it is the cat. Going in on monday to be replaced .

M Carr

See Mike's discovery of affordable new cats - http://cgi.ebay.co.uk/MG-ROVER-MGF-1-8-91-00-Exhaust-Cat-Catalyst-Convertor-/290411410690?cmd=ViewItem&pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item439dde7502
Rob Bell

This thread was discussed between 03/07/2010 and 09/07/2010

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