Rep Power: 156

So I replaced my cat today. Ended up dropping most of the exhaust so I could break the cat apart from the exhaust piping. Here's what I did:

Drove the car up on ramps and also jacked up the rear of the car to give me more room to work. I would suggest going ahead and taking the rear passenger tire off as well. The bolts that connect the cat to the exhaust pipe are rusted onto the bolts so tight I couldn't break them loose. One problem is because of the rest, the other problem is when you try to apply an torque to the bolt the exhaust moves. So it's hard to get leverage without feeling like you're going to rip the exhaust off the bottom of the car.

First unplug the O2 sensors and remove them from the exhaust.

After removing the rear passenger tire you can see the junction of the resonator to the muffler. Spray some WD40 on the bolts and let it sit for a few minutes. Then you should be able to break it loose with a 12mm socket. These bolts come loose from the spring side, so make sure you're attacking it from the right side of the setup. The nut side of the setup is a fixed position.

Now climb under the car and loosen the bolts holding the cat to the header. You can spray WD40 on the bolts from the top side of the engine and then loosen them from under the car. Should look like this:


Now you have this loose you can remove the cat and resonator pipe all at one time.


Now comes the fun part. The nuts that hold the two pieces together are so rusted I had to get a little camping propane bottle with a torch on it to heat the nuts and then break them loose with a 14mm socket. I heated each nut for about 30-45 seconds and then was able to stand on the pipes and break the nuts loose and get them off.

I got a Walker #82681 which a CARB certified CAT. From much of what I've read on the site, an OEM replacement is the best thing to get but it's also the most expensive ($700). Next is a CARB certified which is still costly but not as expensive ($350-400). Then there's cheap ones ($150-200) that are likely to fail soon or not keep the computer happy so you'll get a CEL.

The new one fits well and has the O2 sensor holes in exact same location.



The bolts for the original cat were rusted together so I just bought new ones and bolted it back together. I think there should be a gasket in here. There wasn't one in factory connection and I didn't think about getting one before hand. But after looking at the diagrams on majestic honda's website it looks like there should be something in there. So I would suggest ordering one as well when you order the CAT.

Now you just reattach everything and put the car back together and you're ready to go.

 
Rep Power: 368

thanks!

 
Rep Power: 156

yeah! i know it's pretty straight forward but I'm a visual person. If I can visualize it then I know I can do it so hopefully this will help someone who doesn't have much experience but wants to work on their car

 
Rep Power: 0

Dude, thanks for this post! I have been wanting to do this myself for a bit here but my friends keep telling me I need welding tools. Im pretty sure my 2003 Civic SI hatchback should be bolt on as well.

 
Rep Power: 513

Can confirm, K20 cat is also bolt on

source:


Part #4 is the downpipe with the cat. Just buy a replacement cat/downpipe and gaskets, you should be good to go.

 
Rep Power: 0

Is the old CAT worth money? Can one sell it?

 
Rep Power: 223

Yep they're worth money any recycling facility should give you cash for it