That is exactly right. The cat has the active chemical (usually a platinum/paladium alloy, but there are lots of variations) held in place by a ceramic matrix. When the ceramic carrier develops cracks, the vibrations present usually pound the edges away fairly quickly, reducing the size of the pieces of matrix, until there is a lump about the size of a golf ball. That is about when it can fit over the outlet, and cause major exhaust "constipation". Bad news all around. Don't wait. That much back pressure is bad for the engine, and can cause heads and head gaskets to be ruined...

Geo & Kathleen Hahn <ahwahnee@CYBERTRAILS.COM> wrote:  Florian Speier wrote:

> ...is anything
> bad gonna happen if i let it rattle for a couple hundred miore miles? or
> shall i get a straight piece welded in?

When mine failed it eventually packed up and was partially blocked.
Didn't happen immediately (broke loose on Puerto Blanco Rd in Orpy Natl
Mon but didn't clog until I was in Yuma). Easy to know when it happens
as anything above 2000 RPM is unattainable. I wouldn't wait to do
something with it even if just a temporary fix.

Geo H

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