This may help:
Basically the cats get really hot and anything in the exhaust air that is unburned, that can burn, will be combusted when it passes through the cats. This is mostly to catch unburned hydrocarbons I think and converts them to co2 and h20 which is better for the atmosphere If you are dumping too much crud into your exhaust stream from the engine it can build up on the inside of the cats and clog them or cause other issues. Raw oil/coolant/fuel could cause this basically. In some cases too much raw fuel can cause them to overheat I believe and then the material inside the cat can fracture and block itself up etc...
Easy things to check related to cat operating conditions in my opinion:
Basically the cats get really hot and anything in the exhaust air that is unburned, that can burn, will be combusted when it passes through the cats. This is mostly to catch unburned hydrocarbons I think and converts them to co2 and h20 which is better for the atmosphere If you are dumping too much crud into your exhaust stream from the engine it can build up on the inside of the cats and clog them or cause other issues. Raw oil/coolant/fuel could cause this basically. In some cases too much raw fuel can cause them to overheat I believe and then the material inside the cat can fracture and block itself up etc...
Easy things to check related to cat operating conditions in my opinion:
- is your fuel mileage in a normal range? if it's way low you may be dumping raw fuel into the exhaust essentially, if your mileage is too high you could be running lean and have overheating risks which is a separate topic...
- are you consuming oil between oil changes? A small amount (less than half a quart maybe?) could be acceptable between 6k oil changes but I'd want less than that. My 250k 80 needs no oil between 6k mile oil changes for instance. Of course leaks outside the engine factor in here as well.
- are you needing to add coolant to the cooling system beyond a small amount annually to cover evaporation? You don't want to be passing coolant into the exhaust for a lot of reasons. Same for leaking it externally.