How to remove left catalyst?
Unfortunately I can't find an access to release the T10 screws that are attached to the engine exhaust. I have already removed the deflector plate located at the subframe, but I had no success to have enough room to remove those screws.
Any help are welcome.
I also tried to remove the oxygen sensor in order to make room for my wrench, but is is also stucked, but also, ifs I can remove the oxygen sensor I don't know how to remove one of the two bolts that are keeping the catalyst attached to the exhaust.
Thank you.
From the bottom after moving the aluminium deflector
another from the botton
the catalyst after the core was removed
another from the botton
From the engine bay after removing the air filter. I have already sprayed WD40
From the engine bay after removing the air filter
Some tips:
- A wobble socket adapter comes in handy.
- Make sure you have the correct E-Torx socket size. I forget the size, but I believe E12 appears to fit but you actually need to use E14 to get full contact.
- If the bolts are very rusted hit them with penetrating oil and let them sit for many hours or days.
- The other side of the E-Torx bolt is the square nut shown in your next to last picture - it is pressed into the exhaust manifold flange and can come loose especially if you hit the torx bolt with power tool (which may be the only way to break them loose). If using power tool go easy. If it nut comes loose from the flange, the corners will round over and will start to spin freely with your bolt. Try to avoid this at all cost because it will turn the one minute bolt-removal into many hours of trying to get access to cut the bolt. Don't ask me how I know

- Removing the O2 sensor helps but I fond it more necessary when I was re-installing. If you want to remove it use O2 sensor socket (not open-end wrench). It takes a lot of leverage to break it lose so get your biggest breaker bar and make sure you don't crush a finger when it breaks loose.
Consider removing the entire exhaust system and work on it outside the car to minimize cutting, sawing and pounding if the catalytic converter joints/flanges are all rusted and seize (I hope you know it's not a good idea to arc well on the car if it comes to that). It may sound like a lot of work but if you have cordless impact or air tool it goes pretty easily. If it seems too overwhelming by all means don't do it. I shared some general pix to show you what to expect after removal.
Good luck.
Whole exhaust out of car as one unit. A dolly helps maneuver because it's very heavy
Cat converters separated from exhaust flange
Tack welded flange nut
I will have to buy some more extensions and a u-joint to reach the bolts that are keeping the catalyser stucked, the left bolt of the left catalyser is very difficult to reach.
I have already managed to remove the right and the rear pipe exauhst, my problem is just this left catalyser and the oxygen sensors of the left side, they are all stucked.
Since the past month I have been applying WD40 penetrating oil to the bolts and oxygen sensors with no success in removing then, but someday it will be out.
Once again, thank you!
For extension find ones with ball end like the first picture so that they can wobble. I think I used the wobble extension without the swivel joint and that allowed the socket to swivel enough to catch the bolt. Once it's on the bolt you can lock it like depicted in the "inserted fully regular use" and then apply maximum leverage.
For penetrating oil get PB B'laster or Liquid Wrench. WD40 may not be enough for seriously rusted bolts. You do need MAXIMUM leverage to break loose the O2 sensor. Use a 1/2-inch breaker bar and proper O2 socket. I have yet to see one that came out easily the first time without a fight on any car.
Wobble extension
Get this type of universal joint from your favorite tool line...
Trending Topics
I didn't know about this "swivel joint", as I have not bought the u-joint yet, I am going to start looking for it. Also, I will try to import the PB blaster air liquid wrench as I have never seem them here in Brazil.
The Best of Mercedes & AMG



