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MG MGF Technical - Rattling catalyst

The rattling sound in my exhaust system appeared to be coming from the core being loose inside the catalytic converter. As it is still working (MOT passed) I’d rather not replace it. If I do not fix it, the core will wear out from rattling about in the housing. Splitting and re-welding the body is one solution but if anybody else have experiences to share about how to fix it I’d be very grateful.
Jon

Jon, if the core is shot, then the cat will need replacing. However a rattle could also be due to a corrosion damaged outer heat shield: it corrodes along its lower edge, allowing it to 'flap'. Is this possibly the cause of the noise in your case?
Rob Bell

A cheap option would be to get a cat bypass pipe, and keep it in storage for MOT's.
Richard
Richard

2nd hand CAT from the MGF centre for £40!
Bob Millar

What ever you do, make sure you get a set of nuts from MGF Centre or Mike Satur.
Richard

On my recent journey to the underside of my car, I found that the heatshielding had corroded away as Rob suggests, but thanks to a cleverly placed jubilee clamp round the body of the unit, it's fine. I have not done this myself it was like it when we got under there but it seems pretty solid and sailed through the MOT (phew!!)
Phil

The core is definitely loose. I know, because I took the catalyst out this morning. Had to heat the nuts bright red to shift them.
The core is sliding back and forth nearly one inch inside the shell.
Think I'll just heat the shell and give a few blows with a hammer at both ends of the core. When it cools it will probably shrink sufficiently to keep the core from moving.
Thanks for the tip, Bob, but a secondhand cat from a breaker will double its price before it reaches me i Norway (non-EU).
Anybody's experience with power gain after fitting a bigger high performance cat in a stock 1.8mpi?
Jon

>>Anybody's experience with power gain after fitting a bigger high performance cat in a stock 1.8mpi? <<

One, maybe two bhp Jon [see http://www.mgf.ultimatemg.com/catalysts.htm ]. Only worth fitting if:
a) you're replacing the cat anyway (sports cats aren't all that much more expensive than an OEM MG Rover catalyst)
b) you're considering other engine mods in the future, where the better through-flow characteristics will benefit you more.
Rob Bell

Jon, a loose and broken internal core of the cat will cause damage to the engine, the particles will find their way into the combustion chambers and wreck havoc with the engine, the ceramics are extremly hard particles. I have recently had to strip and replace 4 pistons and liners and rework the valves/seats for a customer that had this problem and left it.Much more expensive than a new cat.
Mike.
mike

Mike, my catalyst core is not broken. The shell was just too roomy, allowing the core to slide inside it. Some kind of ceramic bond was what I was looking for to make an easy fix. A welding torch and a little blacsmith work has cured the problem now. It remains to see how long it will last, though...
I appreciate any temting offers on a new cat. And I wonder how particles from a broken catalyst can travel against the exhaust flow?
Jon

john, had the exact same problem very recently. same symptoms, what i did, actually did this 2 days ago,was took the down pipe and cat off, seperated them and blew an airline through them both, just watch the crap come out. like yours, my cat is ok aswell as it passed ats mot recently, so i left it off and stuck on a cat replacement pipe and will out the cat back on for next MOT.( as a few have already said) CAt pipe was 50 odd quid all in, i now have the car running very sweet... no annoying metallic rattling anymore.

GC.
G.C

This thread was discussed between 18/11/2003 and 20/11/2003

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