Q: How difficult would it be to replace the catalytic converter on my 1997 Chevy Blazer?

Hello. If the exhaust system is original, that is if it is about 20 years old, you will probably end up replacing the entire system, consisting of the "Y" pipe coming off the manifolds, the converter, muffler, and tail pipe. The reason for this is that the catalytic converter mates to the "Y" pipe on one end and to the muffler on the other via flanges with three bolts per flange. These flanges both rust shut and are typically weakened once bent (installed) years ago and thinned out by rust.

You can sometimes attempt to salvage existing parts by using aftermarket flanges and/or split flanges but if the rest of the system is even as little as 5 years old it is not worth it. Also, in your configuration the converter is not set up with straight pipe on either end making retrofit to the existing system less convenient.

If you do replace the whole system, the most critical task is to remove the three nuts on each manifold flange stud without breaking or damaging the thread on the stud. If you haven’t done this before, I recommend that you at least observe the procedure while someone trained completes the job, and then next time around you may have the confidence in taking on this type of job after seeing how it is done. It is a bit of work, and unless you have dealt with exhaust fasteners before, it can be tricky. If you would like a professional handle this, a certified professional from YourMechanic can come to your car’s location to inspect the rattle and replace the catalytic converter for you if necessary.