I have replaced cats on 3 vehicles in my life. Each time, I spent the time and chose a reputable brand, with good feedback. Each time, the cat went bad again within a year or two, and the code would come back. The cheaper cats are cheaper for a reason, and are almost worthless at a scrap yard compared to OEM for a reason. The Honda odyssey I removed the cat from fetched me over $200 at the scrap yard. The replacement that I replaced on it a year or two later, $20. This time I just cut it off and placed a pipe in it’s place. It’s an 03 model, and I hate to do that. However, The emissions even with the reputable replacement wasn’t even close to what it should have been and this van is going to the heap soon anyway.
Every time, I check and make sure it’s not burning oil, coolant, or any other type of thing that will damage the new cat before putting it in.
Anytime I did this, it was always a 10+ year old car, I always needed a grinder, the bolts always snapped or were rusted to pieces.
Usually, I just ended up
A: Cutting out the bad one, and welding in the new one
B: Cut out the bad one, and clamp the new one
Just depends on the location, and the value of the car to me.
If you have to remove the manifold, or do anything like that, if it were me, I’m either not doing it, or taking it to a shop. Every attempt at that has resulted in having to replace much more than just the CAT/exhaust. Usually the header is all rusted, and bolts need drilled and tapped when the break off, etc.
It’s a fun project, but don’t do it unless you have another ride is all I’m saying 🙂
I know in the future, I’m just going to deal with the code unless it’s giving me performance issues, Especially if it’s an older car unless it’s worth replacing it with an OEM cat.