Bosal Catalytic Converter Pipe install on a Mercedes 2002 E320

My wife came home with one of the catalytic converters rattling like Chinese New Year.  Having lived in California for a few years, I figured I was out a shit ton of money.  This ends up not being a big deal at all... since I live outside of CA...

Mercedes rear catalytic converters go out right about 80K miles.  My right rear one went out at 79.5K after 11 1/2 years on the road.  I decided to do both sides with mail order parts since I'm sure the left side is not long for this world.

As always, I'm just a dude with some wrenches and a camera and internet access.  I have no idea what I'm doing and following my advice might just get you killed.

Lots of Options

There are lots of manufacturers making bolt up exhaust systems including Magna-Flo, DEC, Walker, and Bosal.  Magna-Flo also makes a cut-in, weld up parts that if you aren't a welder will take a trip to the muffler shop.

The orginal part numbers are 2104908020 and 2104907920 which are NLA.  Mercedes sells remanufactured pipes under part numbers 210490964788 and 210490954788 which will get you smog legal in NYC and California with a core charge of $150 per pipe.  I was told if the cat is rattling, the core charge will not be honored and these pipes aren't affordable unless you go with one of the whole sale mail order Mercedes parts outlets.  Shipping exhaust pipes is expensive!

Bosal was the most affordable option.  There is an excellent write-up of a Bosal install on a 4-matic E-Class where the right side pipe did not fit.  I couldn't find any feedback on rear wheel drive E-Class cars positive or negative.  I found two things that made me go with Bosal.  First, their video of how they manufacture these parts shows there is an obvious large investment in their facility.

Secondly there were $50 off coupons coming my way from Advanced Auto Parts around Thanksgiving.  While the part drop ships direct from Bosal, I can return the part locally at Advanced without having to ship!  Nice!  Advanced got my biz easily on this one.

Parts

• Bosal 099-1530 - Right side pipe
• Bosal 099-1533 - Left side pipe
• Mercedes 126-997-00-41 - Right side front muffler seal ring (crush collar)
• Mercedes 202-492-02-81 - Left side front muffler seal ring (hard collar)

The Mercedes seals are cheap online or you can use the Walker versions which are more expensive but can generally get free shipping.  I was able to reuse all bolts and nuts as I had almost no corrosion on the system.  I did shorten the exhaust manifold connection bolts by 7 to 8 mm (see below).

Removal

BenzWorld.org has a great write up this job.  Unhook the 4 O2 sensor connections and cables first.  The outside exhaust manifold connection bolts are easier to get at if you drop the sway bar out of the way.  No need to remove the end links, just the frame bolts so the bar can be moved down a few inches.  Be careful as the sway bar torx bolts have a boat load of Loctite on them out of the factory.  I loosened the bolts manually and then put an impact wrench on the bolts to remove them and one of them got stuck 1/2 way and stripped the torx head badly.  Pretty weird.  A U-Jointed 13mm socket was needed on the right outside exhaust manifold flange bolt.  All other bolts came off easily with some Kroil oil soaked in for a few hours.

Bosal compared to Mercedes

Here is how the parts arrived from UPS.  I think I found one ding on both pipes.  Pretty amazing.  Both UPS drivers were into cars so that probably helped...

The label on the rear cats takes a while to peal off.  I found pulling with the grain of the steal, front to back vs. side to side works best.  If you don't peal the label off you end up with a stinky Mercedes for a few hundred miles.

 Side by side you can see they match up well.

The front cats are tiny compared to the original Benz.  Notice how the Benz part takes 5 welds while the spun diameter reduction on the Bosal only takes two welds.  That is really cool manufacturing right in the USA.

 

The bolt up flange plate for the Bosal is made from 1/2 steal plate while the Mercedes part is 20mm thick.  I cut 7mm off the exhaust manifold pipe bolts so that the bolts wouldn't make contact with the exhaust manifold and leave more bolt showing to catch the rust monster.  Also notice the entrance flange is welded on for the Bosal while it is press formed on a continuous pipe for the Mercedes.  +1 for the Germans...

 

This is the orginal left cat sitting low to the ground while the Bosal cat is nicely tucked up behind the motor.  No air cooling for the Bosal.

   

The mid section bracket on the Bosal was huge compared to the original but only on the left side.   The right side was just a bit bigger.

Here are the rear cats.  While the Bosal has a longer catalyst insert, it is certainly skinnier.  My left side had a crease rolled into the ends of it close to the catalyst while right side did not.  The left side's off center rolled cone section is also an interesting manufacturing feature.  The right side is straight pipe and has a mark which looks like a Quick Response QR Code etched into it while the left side did not.  The left side had a more aggressive flat section in the pipe that goes under a frame element than the original Mercedes part.

 I Smell Lean

Obviously I'm geeking out on this job more than usual.  The parts shipped directly from Bosal even though ordered through Advanced Auto Parts.  I received the parts in early December and they didn't exist 3 months ago.  Both were built in small lot sizes (40 or 50 in this case) reducing inventory.  Bosal sounds like a Lean Manufacturing shop.   Considering the crease in the left rear cat and the lack of a QR code, my guess is an older robot made the left rear cat and the robot featured in the video made the right rear cat.

Fun with boroscopes

I stuck one of those cheap $20 USB endoscopes  down the pipes through the O2 sensor hole in the middle of the original Mercedes right pipe expecting to see carnage in they catalyst considering the noise.  I ended up finding clean honeycomb. 

Old Mercedes Front right catalyst entrance

Old Mercedes Front right catalyst exit

Old Mercedes Rear right catalyst exit

I couldn't figure out how to get the boroscope past the flex collar in the middle of the right pipe of the Benz part.  The Bosal right catalyst appeared more yellow.  That might change with a few thousand miles.

New Bosal front right catalyst entrance

New Bosal front right catalyst exit

New Bosal rear right catalyst entrance

New Bosal rear right catalyst exit

Installation

Its really hard to see if the front of the pipe is mated correctly with the exhaust manifold.  You pretty much have to rotate and roll up and down the pipe until you feel its centered, slowly tighten the flange and repeat.  Cut the bolts shorter for sure.  I usually run a tap on backwards, cut the bolt with a dremmel, grind a bevel in with a bench grinder and straighten the threads with the tap by spinning it off.  I used lots of Versa-Chem 13 thread lubricant on the 02 sensors and the exhaust manifold bolts. I cleaned the rear muffler flanges with steal wool.  The crush collar is pretty cool.  Install the left side first (I did the right side, drove a few weeks and then did the left side and the right pipe had to be loosened and pushed in about 1/2 inch.  I didn't reinstall the bracket which clamps the left and right side pipes together in front of the muffler.  The Boral pipes are 2" outer diameter while the Mercedes pipes are about 55mm.  The bracket would need to be modified to use on the Bosal.  Don't think its needed as the pipes are very secure.  Clean the old thread loctite out of the sway bar mounts/bolts and loctite them back in.  I think everything was torqued to 20Nm.

Conclusion

I saved a ton of beer money with the Bosal parts.  I'll update this blog with driving impressions and costs once I sell the old cats to a recycler.  I probably would have gone with the Magna-Flo part if I had the 4.2 liter V8.  The Bosal seems fine with the 3.2L V6.  Probably fine with the V8 too, not sure.  The fit of the part was superb.  I would think the 4-matic part fitting issue was addressed by Bosal since the parts shown by the Benz-World poster had the older multi-weld cats, not spun like the new parts and Bosal's use of small batches.  I have no affiliation with any of the vendors, just a customer...