Repair-It

All the other crap is in case you need to remove the tensioner, it looks like. Notice the part number call out for the tensioner tool.

I got the exhaust pulled apart and welded back together and the cat up in place. Still need to fix the driveshaft, decide if I'm doing the transmission service while I have the radiator fan and part of the air intake ducting out, and reinstall everything.

Made a "fixture" to hold the exhaust system in place while I cut out the sections needed. Wound up pulling out the rear resonator and replacing pipes on both sides. The front resonator was already directly welded to the stainless "adapter" to the cat with no steel other than the weld filler. Looked ok so I left it. 3" stainless from Advance was a very close match to the stock diameter - likely only the heavier aftermarket wall thickness was the difference. Only burned through in like 2 places.

I'm not proud of the weld workmanship, but I think it's plenty strong and hopefully very few or almost no pinholes. All stainless other than the front weld filler now I think.

Hopefully the fit up is good since I tried to restrain it and I marked out all of the support locations/brackets on the concrete floor to make sure they didn't slide around while fitting the new one.

I had forgotten how ornery the stainless wire was to feed through the gun and getting stuck in the gun tip.

Is there a preferred break in process for a new cat?

I got everything back together except the belt - I may have to make the tool if I want to use the car in the next couple days. Apparently it's a T60 torx - I could weld the socket to a piece of flat stock

I might be able to set vice grips on the T60 socket and wiggle that in there. We'll see.

rpaoness wrote: Wed Sep 10, 2025 12:44 pm Is there a preferred break in process for a new cat?

No

All back together. Had to make a temporary tool to move the tensioner to get the belt back on. I guess it’s t55? I’m going to order the tool.

Had a pretty bad hit of the exhaust on the transmission rear pto casing that I didn’t see. Made some bad vibration noises. Fixed that but still have some minor hit in the back mostly on decel.

Reset codes and the cel was off.

Drove to MA today - “permanent” codes cleared after the 2nd key cycle. No cel still.

How does it sound now?

A little quieter but not a ton. I think the aftermarket resonators likely killed the original sweet AMG exhaust note. The rattle from some contact I created is also annoying enough that it isn't really any fun whaling on it until I get that sorted.

Since I'm also much more comfortable beating on it as I drive it more, I suspect the rear diff is noisy. I've read those are a vulnerability and I haven't even checked the fluid level yet. I wonder if it's on its way out.