Catalytic converter?

[Sloan]

What is the best way to tell if one is bad or in need of replacement? What am I looking for during a visual inspection? Thanks!

 

[ntsqd]

What is the best way to tell if one is bad or in need of replacement? What am I looking for during a visual inspection? Thanks!

Is it off the vehicle? If so, you can look thru most modern cats. Can actually be partly plugged and still be able to see through it, so don't take light visable as total confirmation that it's good.

Engine running warmer than it used to? Plugged exhaust can do that.

Hear a rattle on bumps that you can't ID? A loose converter core isn't uncommon in O-R driven vehicles. I had one get loose enough to turn sideways in it's housing.

Best test that I've found is to ask my friendly test-only station to check the emissions. That will point to one if it's not working right.

 

[R_Lefebvre]

It's really difficult to tell, even if it is off the car and you're looking right at it. I have tried to analyze the one from my Focus, and I can't see light through it whether it's new or old. I could only judge the basic condition of the matrix I could directly see.

 

[njtaco]

In my limited experience...using an IR thermometer...

Take its temperature...hot going in , hotter going out, probably OK

Hotter going in than going out, not so good. Cat not operating, may be clogged.

Same temp going in as out, cat not working, may have been..."clearanced"

No hard and fast rules here, the air injection plays a role, too. This is just where I start out, after a failed emmissions test or running problem.

Hope this helps...

 

[DaveInDenver]

Are you failing emissions? Other than mechanical failure, you know rusting out, baffles breaking, plugged up, etc., the only other thing that requires a cat replacement is the catalyst being exhausted and that'll show up in high HC, CO or maybe NOx readings. Other than njtaco's temp readings, not really much you can tell until you have the tailpipe sniffer in there.