But is a total waste of time and money IF you have a stainless steel exhaust system. I don't know if the Prius models have that or not.
Weld seams are the most important as they are the first thing to rust on Toyotas rust resistant or even on some "stainless steel" exhaust systems. But unfortunately paint just doesn't stay on forward facing seams do to sand blasting effect while driving. And a lot of rusting happens from inside out only thing that you can do to slow that a bit is to drill a drain hole to let the water run out.
There should be at least ONE drain hole in the pipes/muffler somewhere........and that often is the first place to show signs of rust.
I just replaced my cat with an aftermarket setup. I get a whiff of exhaust, so I will be replacing the donut and see if that helps.
There are many mufflers without drain hole from factory. Drain hole is (sometimes) first place to show rust because of inside out rusting. But drain hole is still slowing the inside out rusting.
The actual muffler may not be the lowest point in the exhaust system. The lowest point is where the drain hole is usually located and that might not be the muffler. Some vehicles might not have one at all .......but I don't remember seeing one.
I didn't see one when I was under the car a week ago. I was tapping on the Cat for the sounds of loose catalyst, didn't hear any rattling.
If muffler is not the lower point of the system it still normally has local lowest point. So water collects to the bottom of it.
I have never heard of a car having a drain hole in the exhaust. They get dried out from the heat of the exhaust gasses. Have you ever owned a car that had a hole in the exhaust from the factory?
Yes. ALL of them somewhere or another. At least all of them that I looked at. It often looks more like a defective seal at a joint than an actual hole. But some of those observations go back 30 years or more. And how much "drying out" that occurs depends mostly on the length of the pipes. Since the addition of the cat converter, there is a lot of heat dissipated there so the muffler and tail pipe should be cooler.
Since my state has been in a drought for about 9 years, and it is a TX car, I'm not inclined to think water has created a point of failure. That said, this is the first time exhaust has been suspected in the 18 months I've owned it. More likely I'd believe the underside has been subjected to many scrapes with the roadway. Everyone in this forum says the Gen 2 has weak suspension.
