[Drew303]

can you tell that a catylitic converter is bad by looking at it? i mean my car was up on a lift and the piping was fine but my cat has rust all over it for some reason..

 

[RyanD]

i'd say it depends on the severity of the cat. If it's completely rusted through from the outside and you can see the inside, then i'd say it's time to change it.

Otherwise, you can't tell just by looking at the outside. It's the inside you need to be concerned with. If the rust is BAD and is moving to the inards, change it soon

 

[joehotrod]

look inside and see if it's starting to melt or deform