Miata Mailing List: November 1998, Message #108

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For the last few weeks my cars had an annoying buzz right on 3.5k revs...   
especially when cold...

Heatsheilds loose or broken I hear you say?

Slight problem, my car has Jackson Header and cat-back... very few   
heatsheilds left on it...

Any way, by gently tapping different parts of the exhaust with a block of   
wood, I narrowed it down to the cat. Oh no, couple of hundred bucks..   
here we go....

Anyway, I took the cat off last night, expecting to find lots of loose   
catalyst inside...

Well the insides were fine, but a whole lot of dirt and small stones fell   
out from between the cat body proper and the little heatsheild it has   
around it... Bang it about a few more times to dislodge any other bits   
and pieces, put it back on and no more buzzing...  Yippeee.

Come to think of it, I do seem to remember grounding out in some gravel a   
couple of weeks back....  ;-)

I was sorely tempted to ram a broom-handle right through the thing   
anyway.. but in the end I decided to be green ...even though cats arent   
actually required here in NZ.

So if your cats a buzzin, it might just be because it got a little gravel   
rash....

Fletch.

P.S. anyone know for sure whether the Ceramic coated JR header is   
stainless or mild inside the coating? I think it may be rusting slightly   
where the gravel rash got through the coating...