Those rubber hangers break; that's just the way it is. Order some over the internet with a couple to spare and keep an eye on your muffler and pipe.

I actually could not get them back on. Luckily, I save all the o-rings that come with my oil filters so, in place of each hanger, I doubled-over four o-rings (to make the diameter smaller) and used them to hang the muffler. Around each set I also tightened a hose clamp for good measure. Should hold just fine for the day.

The PC-7 seems to be the easiest, definitely the strongest, and will go on smoothest. I also considered putting a ring of PC Fahrenheit around it, or would that be unnecessary?

Curiously, the day after I began hearing the exhaust noise I had the car inspected and is passed with no problem. It's possible the crack was much smaller, or simply not visible from the angle the inspector was viewing the exhaust system from.

I will be having it looked at by the welder shortly. If he cannot do anything, I will go this route. Now that the muffler is secured again, I am not worried about further breakage, but will inspect everything between the resonator and the cat in case something else was damaged.

OK, what is in the photo can now best be described as a hole. An actual narrow crack runs around the other side of the pipe about 2/3 of the way down. Can't be welded because of the rust, but can be sealed. There is also a sleeve within the pipe which can serve as a convenient substrate for the sealing material. From the resonator to the engine, the exhaust is solid.

I looked for PC-7 but was told at Home Depot the company no longer manufactures it. (They nonetheless still have some on their web site.) He said they are moving towards the more universal putty-type products, like PC Fahrenheit, which they did stock and which I purchased.

I also stopped at Autozone for a patch kit so I could scavenge some wire and refractory fabric from it. The plan is to scrub down the pipe, wrap a narrow strip of fabric into the crack, then some wire, and then ring that with the PC Fahrenheit at approx. the width of the gap at the top. As long as the rear muffler does not bounce, it should hold. But if there is flexing, all bets are off and I'm looking at a replacement.

I also picked up new hangers from the dealer. According to them (HBL in McLean, VA), MB is now using the round donut rings for my car. Since the oval/crossmember units are available in AllPartsExpress, I doubt that assertion, but since they were only $2, I won't complain. Also, because I intend to keep those hose clamps around each hanger to make sure they do not flex, the round ones are actually preferable.

EDIT:
Seems the patch kit also contains some foil. So that will go on first, then the fabric, the wire, and the PC.

I'd go find another welder. A gennie MB muffler is worth saving, and the right way is to get it mig welded. If the metal is not too thin, the rust can be removed with a wire wheel on a minigrinder and the hole/crack filled in several passes using low heat setting. Or, simply cut out the bad part and weld in a replacement piece of pipe. This kind of work should be duck soup for any competent muffler shop IMO. I've done this kind of repair many many times, and on parts way worse than the piece you pictured. PC7 or JB Weld or whatever will not last because of the flexing, so I wouldn't waste my time. This kind of repair is best done at the bench with the piping off the car, but it can be done on the car with some patience.

Based on what you said, I called another shop who said they could replace the "D Pipe" and clamp it (they don't weld). Does that make sense?

There isn't anything to clamp onto... I think you will get a different answer when they see it. I agree the epoxy stuff will have issues with thermal expansion cycles. You would want the biggest gob possible. And if you have state inspection where they look at the muffler it won't pass.

donbryce gave the kind of answer you will get on the welding site. These guys are scientists. They have to learn all kinds of metal chemistry stuff. They don't explain it that way but that is what it is about. Yes a good weldor (person) can fix it. A bad weldor can screw it up.

I used to live in Fairfax BTW.

Yep, they had a deer in the headlights reaction when I arrived at the shop and described to them what I needed.

Somewhere in Manassas, there is a guy (or gal) able to weld a replacement pipe and I'll take my search there since I won't get any satisfaction from the corporate shops around here. :) In the meantime, I'll form a temporary fix with the PC Fahrenheit.

Heat and mechanical flexing is a big concern, and part of my motivation for doing the foil-fabric-wire layer was so the PC-Fahrenheit would kind of float on top of that, with just a portion of it adhering directly to the metal. I conjectured that a ring of this type would not need to seal the leak entirely, but just block enough exhaust gas to eliminate, or significantly reduce, the noise. (The pipe has been cracked for a long time, but I only began to hear it last week, so some escaping gas is not a noise problem.) Also this should make it easier for the welder to clear the epoxy away.

What part of Fairfax where you in?

You are wasting your time and money, doing a patch job. A good muffler shop - a good welder - can take out the section of nasty pipe you have there and replace it by welding it directly to the good muffler and to the existing pipe before the rusty part.

Replacing MB muffler hangars is much easier if you support the muffler in place with a small jack.

I realize that, and that is my intent. But first I need to find the shop/welder able & willing to do it. So far, I've been striking out, so in the meantime I will do the patch to keep things quiet. I d not expect it to be permanent.

My knee works pretty well also. :D

Greenbriar. If you know where that is.

I sure do. I used to date a flight attendant and passed Greenbriar a lot on my way to and from Dulles. I still get out that way quite frequently.

Aahhh... Delightful silence. :)

I have a ring of PC Fahrenheit over the crack. (Installation: Thin layer of PC Fahrenheit; foil strip; then successive rings of PC.) Smoothed and shaped, it looks like a slight extension of the neck of the muffler. If painted gray, you would likely not know it was there. Should last long enough for me to find a welder.

An old Bean can and two muffler clamps.

Cut the can lengthwise (after removeing both top and bottom) then wrap around the damaged area and muffler clamp away.