When to replace cats?

[Ger42]

How do you know when to change cats? Truck has 81,00 miles on it.
Gerry

 

[fastpakr]

Never under normal circumstances. It's not a maintenance item at all. Occasionally something else in the system breaks down causing them to fail, e.g. running rich for long periods of time, etc... However, that's an exception rather than the rule.

 

[Ger42]

What would indicate a change?

 

[fastpakr]

They get changed if something causes them to clog, and there is a vacuum test you can run to determine if that is the case. Is there some reason you suspect a problem?

 

[doorgunner]

I had little charcoal looking pieces flying out of the tailpipe when I would rev up the engine, the truck started losing power gradually and running hotter (the muffler got plugged up) bad cat bad-bad cat

 

[85_Ranger4x4]

What would indicate a change?

If they plug up or break apart... they can do neither on their own. Plugging up like previously mentioned a tuning problem, and I have heard of wrecked/rebuilt cars having cat problems because of the impact.

 

[Ger42]

They get changed if something causes them to clog, and there is a vacuum test you can run to determine if that is the case. Is there some reason you suspect a problem?

I just purchased the truck with 81,000 miles. I've never owned a Ranger so I don't know what normal would be.

 

[doorgunner]

Well, if you absolutely positively gotts to know for sure, remove the cat (but it'll be a fight&you'll get scratched) & shine a bright light thru it to see if the honey-comb is stopped up But, you may as well shine a light thru a 4-legged cat first--if you can handle that, you'll be prepared to remove the truck cat

 

[fastpakr]

?
There is no need to remove the cat. You can run a basic intake vacuum test to confirm the condition of the cat.

 

[MAKG]

And you can test for a BROKEN cat (as opposed to a plugged one) with an IR thermometer. If the cat is doing anything at all, exhaust will be warmer at the cat outlet than the inlet.

Cats generally don't break on their own (though they can with the aforementioned mixture problems). But idiot previous owners have been known to stick broom handles in there in the crack-induced assumption that the vehicle might get better power that way (in reality, it's almost always an obstruction).

 

[doorgunner]

There. Now he can do it the easy way, or the hard way