Mercedes-Benz Forum banner

catalytic converters

12K views 48 replies 10 participants last post by  anziani 
#1 ·
About 10 days ago I decided to take a "road trip" and headed for Old Route 66, about 130 mi9les from where I live. Well about 90 miles out, the car stsrted missing and the CE light came on. knowing I had a 100 mile AAA card, I turned around and headed back. Got another 3-4 miles and it came to a stop. Desolate desert, no cell phone range and only an occasional passing car. Luckily a guy stopped and we both drove to a higher location where I finally contacted AAA. An hour passed, a flat bed arrived and back home I went.
We determined it was catalytic converter that had blown. Instead of $1000 a piece for MB replacements, I opted for Magnaflows at about $250 each. We also talked to the muffler guy and he suggested that we remove or replace the middle muffler just aft of the CC's because if anything blew past it would end up in the next muffler. It was a good choice becasue now theere is a little "F-1" nosie out of the car. Can't hear anything in the cabin but it is obvious outside. Anyway here are pictures of the blown cat.
Anziani
 

Attachments

See less See more
3
#3 · (Edited)
Alter, The car is a '97 CL600 with only 62K I'll have to wait until Monday to see what Magnaflow cats were installed and don't have a picture yet but will work on it. I am a firm believer in that if one thing goes out, the rest in that series are close behind. While only one cat let loose, I wasn't about to be caught in the wilderness again so I replaced them both.
I really think I picked up horsepower as it now acts like the beast it is!
Anziani
 
#5 ·
Alter, yes we were surprised at why one of the two blew but I have a guess. The car spent it's life in Newport Beach here in Kalifornia. While it is not as humid as the East Coast beach towns it is still humid. The billionaire that owned the car had a Porsche and an Aston Martin. The lowly Mercedes got only 2300 miles per year put on the car. My guess is that the cats rarely got heated up for any length of time and eventually moisture found it's way into one of them. And no the car has never had cheap gas.
I'll know a little more tomorrow when I get my bill and find out why the CE light came on.
Anziani
 
#7 ·
Alter, I can't add much more to this. My mechanic says it is rare for a Benz to lose a cat but fairly common in other cars. Since I live in Kalifornia and everything thing is "special" out here. The cats I used wouldn't necessarily be the best one for you because mine have to pass all sorts of BS to be accepted. Just go to the Magnaflow website and start poking around.
We eliminated the middle muffler and ran straight pipes to the rear muffler. I'm convinced that I've picked up 20-30 HP.
Anziani
 
#12 ·
Alter, I'll post pictures later. I'm having hand problems that are more demanding.
As to the noise, one can't hear it in the car but it is obvious outside or behind. It is exactly what I'd hoped for. Just a hint of a Petronas F-1 car at speed. Not obnoxious but one does look at where the sound is coming from.
Anziani
 
#9 · (Edited)
I can't add much more to this. My mechanic says it is rare for a Benz to lose a cat but fairly common in other cars..
Neil:
Allow me please to add something to this discussion.
Not too long ago, we discussed the following problem of yours:

One thing that DID puzzle us was the presence of "gasoline sludge" for want of a better word in the mouth of one of the throttle actuators. The other one was clean as a "whistle". Do we have a leaky injector that isn't closing on that bank?
This was part of the discussion in this thread:

http://www.benzworld.org/forums/w140-s-class/2743082-wwyd-m120-intakes-off-now-what.html

I raised the issue of the breather system being at fault, but another user brought up the EGRs.

This thread was never "closed" and in retrospect, I think Les may have been right. Let me ask you this -- was the sludge and the plugged cat on the same side?

If so, I think this may have been the early warning sign that something is amiss and if this something was not corrected, your newly installed Magnaflow's will not last very long.

Best regards,
Steve

PS For posterity, I will cross-reference this thread with the other one. I hope you don't mind
 
#11 ·
Neil:
Allow me please to add something to this discussion.
Not too long ago, we discussed the following problem of yours:



This was part of the discussion in this thread:

http://www.benzworld.org/forums/w140-s-class/2743082-wwyd-m120-intakes-off-now-what.html

I raised the issue of the breather system being at fault, but another user brought up the EGRs.

This thread was never "closed" and in retrospect, I think Les may have been right. Let me ask you this -- was the sludge and the plugged cat on the same side?

If so, I think this may have been the early warning sign that something is amiss and if this something was not corrected, your newly installed Magnaflow's will not last very long.


Steve, good point on the "sludge" I'll know more this week on which side it was.
And "sludge" is way too harsh of a term. Discolored would be more like it. With all of the computer scans we've done on this car, no injector problems showed up, in fact hardly anything has ever shown up. When I took it for "smog" last time, I noticed the tech tapping on his gauges since many were reading at "zero". If I have an injector problem it isn't obvious.
Anziani
 
#10 ·
Dont be surprised its been over 10 years and its made of ceramic. A bit of misfire and they go south quick $250 a pop for magnaflow isnt too bad thats what i paid 7 years ago. But then bought some walker cats for 1/4 price. 600 has 2 cats 500/429 has 4 cats. My s65 is need of cats too.
 
#15 ·
Just out of curiosity I looked up the last "smog" test. I assume that HC stands for hydrocarbons. :angel My car at idle was 5 PPM. At 2400RPM it was 8 PPM. The allowable here in Kalifornia is 100 PPM and the average is 14 PPM. If this is a measure of unburnt hydrocarbons, then mine are insignificant.
Anziani
 
#17 ·
Steve, I went back in and looked at your article on the elements that will take out a CC. Only the last two are possibilities but wouldn't a bad O2 sensor show up on code printouts? Am I'm talking Xentry not a Pep Boys under the dash device. Will have more info tomorrow.
Anziani
 
#18 ·
Here are pictures of the new CC/muffler conversion. The exhaust guy did a great welding job. As to WHY I talked to my mechanic who said the heat down here in the desert has a bearing. He replaces cats on foreign cars frequently, not so much on the Mercedes. I've eliminated all reasons for my failure. If the first one lasted 20 years, then I'm ahead of the game because I won't last 20 more years. :(
Anziani
 

Attachments

#22 ·
I looked at the pics and I am wondering if the pipes they replaced are SS or are they CS? They do not look like the SS of the original. Also to get the FI sound you eliminated the muffler between the two cats? or one of the cats?

Lastly I had similar symptoms with the S500. I was suspicious of the cats and asked the mechanic. He showed me silver metal that was in the oil pan. I had them install a used motor which I found online for $2500. Labor and new motor mounts was $2500. As soon as they started there was a problem with one of the cats. New cat installed was another $1200. I still think to this day that the problem was the cat and not the motor.
 
#19 · (Edited)
Here are pictures of the new CC/muffler conversion. The exhaust guy did a great welding job.
Neil:
Thank you for posting the pictures. Just to be clear, this picture



shows muffler delete, not replacement. Only the 3-way catalytic converters are replaced with aftermarket Magnaflow's.
Is this what the exhaust guy billed you for?

EDIT: I looked one more time at the 3 pictures and realized that the muffler shop did not leave any joints. The exhaust seems to be ONE PIECE from the exhaust manifolds down.
If this is the case, I would return and will ask them to redo the job and at least make the rear muffler attached to the straight pipes via a slip-fit joint. This won't be too difficult.
There are jobs that will require you to remove sections of the exhaust system. As is, your car will require the removal of EVERYTHING, downpipes included.



As to WHY I talked to my mechanic who said the heat down here in the desert has a bearing. He replaces cats on foreign cars frequently, not so much on the Mercedes.
I am sorry to say it, but I remain skeptical of this diagnosis.

Earlier in this thread (post #5 from 05-21-2017), you said that the humidity in Newport Beach and the fact that the car got only 2300 miles per year was the reason that "the cats rarely got heated up for any length of time and eventually moisture found it's way into one of them".

Now, too much heat is being put forth as a reason for the premature failure.

Knowing what I know about metals and catalytic processes, I cannot put 2 and 2 together....


I've eliminated all reasons for my failure. If the first one lasted 20 years, then I'm ahead of the game because I won't last 20 more years. :(
Please excuse me if this comment comes across as rude, it is not meant as such. I think we will all be better off if the problem is understood.

In March, another fellow with a 50,000 California car reported melted cats and you and I agreed that this is something abnormal. This is what you said back then:

Cats at only 50K? Sounds like you need to put it on a computer and get all of the codes. And I can't imagine even needing O2 sensors at that mileage.
I bought a '97 Cl 600 with only 46K and those components weren't even discussed. However, I did have a bad MAF.
Anziani
If I were you, I won't be asking your mechanic for the CEL codes -- there may or may not be such -- he needs to verify from live data that the A/F ratio for both banks is proper and consistent.

Best regards,
Steve
 
#20 ·
Question on this

Interesting, mine is a 97 with 178k, maybe the highway driving is what has kept mine working. I am a bit concerned with the 100 or so miles I put on it new, trying to run out what I suspected was bad fuel, and then to get it to my shop. There was a smell, so I'm sure they were taxed even if not gravely impacted.

If you picked up 20-30hp and a nice sound that isn't something that is too "F1" for this car, while I know I've got other item$ ahead in priority, I'd love to know what part numbers you used.

There are a dozen "universal" CARB and non-CARB Magnaflow cats I see online. I am not sure the difference. I don't live in CA so I'm not sure I'd have any need for the CARB-compliant version, but beyond that no clear answer online.
 
#21 ·
California is strict and has to have carb number stamped on the casing of the cat. Secondary cat delete is okay in my books but complete cat delete burns your nostrils and gets you light headed. I had kleemann headers with 3" piping to the factory rear mufflers on my s55k and i would have to drive with my windows closed or else i would be coughing. In California exhaust fine is anywhere from modified exhaust to emissions tampering. One is a $50 ticket and the other is a felony with jail time over a year. But its hard to lock someone up for a car modification they will give a fine. Some people can get ref tickets which can lead to criminal charges but generally speaking if you are not street racing or reckless driving it would be a "fix it" ticket
 
#25 ·
With a resonator delete you will not gain any noticable power its really free flowing. You will get a bit of a rumble and nice sound on the high revs. The rear mufflers are restrictive on the w140. But the horsepower robber is the cats it was a 22hp difference if i remember correctly. The headers are complete garbage on the m119 as well i had the inside port and polished the casting is horrible.

If your cats are damaged you might not even know unless you have owned the car for while and feel its loosing power. If you live in a place were cats are not required and there is no emission testing get some 400 cell metal spun cats to keep the check engine light off and keep the smell to a minimum. I dont know what the minium cell count is for the m120 and m119 but on the m113k and m275 its 200 cells or you can disable the monitoring through star
 
#27 ·
So now I guess it's my turn.

Back in Uganda to continue with my restoration on the S600.

Before I left for the summer, I noticed my exhaust overheat warning light was lighting up. Mine is a Japanese market model.

This car has never been quite as powerful as I expected. I've also never been able to get a proper Lamda reading from the left hand bank. The right hand reads within expected limits.

As I spent about a month driving this beast with one bank dead (combination coil, wires and an improperly seating LH computer), I'm sure at least one of my cats is melted.

So tomorrow, we are pulling the exhaust system (for the 3rd time), and I'll be cutting open the cats (both of them) to see what I find.

I'll post pics of what I find.

Cheers
 
#28 ·
I wonder if replacing my cats with Magnaflows instead of OEM cats would give me a CE light. This happened right after the exchange although the O2 sensors were replaced with OEM units at the time. If the O2 sensors look at a voltage differential between intake and out let and the MB computer is programmed for a certain range, could the Magnaflows change that voltage reading enough to trigger the CE light? That is one of the first tests we are going to do when we get to it. I went to Magnaflow but they didn't have an answer.
Anziani
 
#29 · (Edited)
I wonder if replacing my cats with Magnaflows instead of OEM cats would give me a CE light.
What code do you have?

This happened right after the exchange although the O2 sensors were replaced with OEM units at the time.
You have 2 upstream and 2 downstream. All 4 new?

If the O2 sensors look at a voltage differential between intake and out let and the MB computer is programmed for a certain range, could the Magnaflows change that voltage reading enough to trigger the CE light? That is one of the first tests we are going to do when we get to it. I went to Magnaflow but they didn't have an answer.
Magnaflow did not know? The upstream o2 sensors look at the raw exhaust gases and their voltage signal (typically in the range 0.1-0.9V) is used by the engine ECU, together with other inputs to determine the air-fuel mixture.

The downstreams o2 sensors (only on OBD-II cars) are emissions control.
They make sure your cats work.

Best regards,
Steve

PS BTW, O2-sensors use zirconia or titania (oxides of Zr and Ti metals) which transport oxygen ions at elevated temperatures. They generate their own signal (voltage) based on the O2-levels in the ambient atmosphere and in the exhaust stream. No MB magic....
 
#31 ·
Glepore, no I think it is a false code since there is NO change in performance. My mechanic closed his shop so I don't have access to a Star system at the moment. We got the "timing" code on a "short Test" but did not have time to pursue it. I want to go back in and do a component test (if possible) on the cam position sensors, the crank position sensors, the automatic cam adjusters and (my suspicion) the O2 sensors. At first we thought there might be a problem in replacing the new engine harness but 6 months went by after the replacement until the CE light lit off. And it lit off a week or two after the CC/O2 replacement.
Since there has been no drivability problems I can't believe it is a "timing" issue. My first chore is to find another mechanic.
Anziani
 
#32 ·
So, today I pulled the exhaust system off to inspect the cats.

What I found (not surprisingly) was that someone had been in the cats before. The drivers side (LHD) had been cut open, and the honeycomb was removed. The right side was untouched.

So after cutting it open, I found no honeycomb in it. But, there were several steel pieces that look like they would be the housing/holders for the matrix. They were blocking the inlet pipe.

So I suspect that the unopened side blockage was responsible for the out-of-range lambda readings I was getting on the passenger bank.

I'll be putting the system back together and reporting on how it runs tomorrow.

But this explains why the car is louder (esp from outside) that I expected. It had that ratelly tin can sound.

I think I'll be bringing back a new set from the states in November.
 
#34 · (Edited)
Searching for cat replacements, I find 4 types on eBay:

Does anyone have an experience with any of these?
Don't waste time/money on these aftermarket parts. If your only problem is the melted cat, buy just the converter, like Neil did, and have your guys weld it in place.
The OE MB pipes will outlive the aftermarket ones 10 times.

A discussion on melted cats also happened recently in Joe's thread:



Start at post #44
http://www.benzworld.org/forums/w140-s-class/2792362-joes-600sel.html#post16395210

Good luck,
Steve
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top