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New converter or repair?

I just brought my car into the shop for a loud muffler. The guy told me I need a new converter and two flanges I believe they were called.

So is this the,part I need. Just want to make sure before I purchase it.

We can’t see your exhaust system

Are they saying you need a catalytic converter because it’s plugged up, or because it’s rusted out?

Is your check engine light on, by the way?

I’ve never seen a rusted out catalytic converter. That’s because catalytic converter bodies are made of stainless steel.

If the Check Engine light isn’t on, get a second opinion for your exhaust repair.


Actually I had a cat rust at the flange. Came apart and really made a racket. I was only a mile from home though. The relative in the muffler shop welded the thing together again and it held for a couple years. Then I had to replace it. I got mine from Rockauto and it was fine. If you are going to be ordering parts for a shop to put on, you had better be talking to the shop with specific part numbers etc. to make sure.

I use to make prototype catalytic converters for testing.

And according to the EPA, the body, pipes, and flanges must be made of stainless steel.


on my 2006 Pathfinder both upstream and downstream converters were made from rusting steel, one failed at the pipe/flange connection and I had to replace it with a stainless one

IMHO that “stainless” requirement might have happened past 2006

I’ve had both cat converters rust out on my 03 Passat. the first under warrantee (barely) and the second not. Actually it was the connecting pipe that rusted through, but it could not be replaced without replacing the cat.

I live in southern California, and I’ve seen several rusted out catalytic converters

And btw, these were California-spec vehicles which spent their entire lives in southern California

And I tend to agree with Andriy . . . but I’m not sure about the dates

I clearly remember catalytic converters from the 1980s . . . and maybe even the early 1990s . . . were made of material which was far inferior to stainless steel

And when I say rusted out, I mean the catalytic converter itself, not just the pipes or the flange

Surf over to, plug in your vehicle description. Best way to uniquely id the vehicle for part compatibility is to use rockauto’s vin number method. Once you’ve got it id’d, then search for catalytic converter and it should show you all the ones they have which are compatible. If you live in a state that requires emissions testing, Calif for example, look carefully in the listing what it says about each cat, so the part number you buy is allowed in your state.

Stainless steel comes in a lot of different grades, and if you heat stainless steel enough times, the cheaper grade will rust especially in the presence of the salt bath that is our roads in the winter. Our muffler shops replace rusted out cats all the time. Even the stainless steel exhaust systems most cars come with now only last about 10 years here on a daily driver.

My latest gas grill which has a Stainless hood had an owners manual that says the grill must be stored inside or covered to prevent “staining” in the presence of salt. The staining they are referring to is rust. My last grill was 5 years old and the stainless was mostly reddish brown.

It really is a topical rust stain. 300 series stainless, the kind we are most familiar with, often has areas of the surface without the chromium-nickel alloy that is rust resistant. These areas of iron on the surface will rust. It’s the same thing that occurs in your stainless kitchen sink if you leave a steel pan or pot on it too long. This rust can be avoided if the metal is treated with nitric acid, but this is impractical on a finished part like a catalytic converter.

We discussed a related topic in another thread a while ago about whether or not a magnet will stick to stainless steel. Turns out the answer is “yes” for some versions of stainless, like the kind used for knives, & “no” for others, like the kind used for pots.

I had a split catalytic converter noted during exhaust repairs, the bender center welded it together for $10, rest of the exhaust new with lifetime warranty on the muffler $125. 6 years later muffler went, $2.18 because I needed a new muffler clamp. Explore your options!