MOT tomorrow (wish me luck!)

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CitroJim
A very naughty boy
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Re: MOT tomorrow (wish me luck!)

Unread post by CitroJim »

Mandrake wrote: One thing I've always noticed about this car is the exhaust system gets REALLY hot, I'm not sure if its the exhaust header/downpipe before the cat, the cat itself or both, but even after a very short drive the moment you switch the engine off there's a loud "tick tick tick" of the exhaust cooling down that goes on for a few minutes...and it still does it. Could it be the sound of the cat getting really hot working really hard trying to clean up un-burnt HC ?
That's normal Simon. They do get very hot very quickly and stay hot for a very long time afterwards. I know from a nasty burn I got from swapping an oxygen sensor once...

As I understand it cats have to be very hot to work effectively anyway...

Mine tick like ten bob watches so no worries there at all...
Jim

A bit of a Citroen AX fan...
addo
Sara Watson's Stalker
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Unread post by addo »

I think the ticking is differential rates of cooling for the heatshield vs cat housing. The matrices themselves are banded in stainless wire, so if they make noise it's probably a sign of fragmentation.