Cat keeps braeking up! - PeachParts Mercedes-Benz Forum

standard125r · #1 08-10-2003, 03:10 PM

Here the question: What would cause a Cat converter to break up inside? This is my 3rd one in three weeks.... The original was replaced last summer after my MSD ignition shorted causing a terminal meltdown it lasted until July when I got a banging sound inside. I drove it for awhile then I started losing power and engine temp started going through the roof. When the cat was removed it was replaced under warrenty, because it was al broken up and many of the pieces were gone. This was while using a stainless muffler from Aerospeed. One of the baffles in said "muffler" was loose and there was concern that possibly reversion was occuring causing the catalist to break up. That cat lasted 4 days in which I drove under 200 miles. So, in frustration a pipe was welded in while I waited for a new muffler. I got a nice ANSA muffler AMG style then ran all new pipe w/ a high flow
Catco cat. I have traveled 1560 miles since last Thursday(the day I picked it up), and it is already banging away. Is there a solution? Is it somthing simple? The catilist has not been melted on any of the removals.

P.S. this is on a 190E 2.3 16v if it makes a difference.

psfred · #2 08-10-2003, 03:35 PM

There is something seriously wrong with either the ignition system, fuel system, or installation. Cat should last MUCH longer than 200 miles!

I'd figure the shop would have fixed this by now, they are going broke on warrenty work!

Check ignition system -- it may still be bad after the repair. You need to check the fuel mixture at idle and under load, too -- going intermittantly rich will fry the converter, causing either meltdown or thermally induced cracking.

And check the hangers and basic exhaust intallation -- if the pipes are banging because they are improperly installed or the hangers are bad, the cat will evenually break up from impact damage.

My money would be on the ignition.

Peter

stevebfl · #3 08-10-2003, 05:16 PM

The car is obviously not running in closed loop.

JimSmith · #4 08-10-2003, 06:22 PM

standard125r,

I just bought a second 190E 2.3-16, Euro model, that has had a cat failure. On my first one, I owned the car until I gave it to my son recently. The cat failed on that car because the pipes coming to it rusted and the casing itself corroded away in 15 years of daily use in the Northeast. I replaced it with an aftermarket unit that fit just fine, and has worked for another 3 or so years. The car has 216,000 miles now.

The second car has 120,000 miles and is on its third cat now. The first replacement occured in 1992, so I don't feel too much like I am heading in the direction of your experience. Yet. But your tale makes me nervous. In the second car when the cat went my wife was driving it and she drove it until the car would not move. It would start and idle but not rev past 2,000 rpm. The car runs fine now with the new cat installed, and it has been running fine for about 1,000 miles.

I can't really offer a solution but am very interested in the way your problem works out. Please keep us informed on how this saga pans out for you, if you don't mind. Good luck, Jim

standard125r · #5 08-11-2003, 07:55 AM

Thanks for the advice. I was under the impression that ignition or fuel problems might cause the cat to melt, but there is no sign of that. I have inspected it on both occasions and found the catilist nearly gone from the inside. The piece that was left had fatigue cracks, but no sign of heat damage.

#6 08-11-2003, 08:31 AM

Catalytic converters come in varying degrees of quality, and can be manufactured for specific vehicles mode of function.

My GUESS is non MB cat= cheepo

psfred · #7 08-11-2003, 09:56 PM

Steve Brotherton is entirely correct (as usual) -- your mixture control system isn't functioning properly, the catalyst is overheating, and cracking from rapid cycles of overheating/cooling.

Get the mixture control system fixed before you fry another one.

Bad ignition will do the same thing, only faster, since you have both extra fuel AND extra oxygen from missfires. Will destroy the catalyst pronto.

Peter

tecqboy · #8 08-11-2003, 10:20 PM

How does the exhaust smell? Raw gas smell? Rotten eggs? Is the exhaust pipe black with soot? Extremely rich mixture will kill a cat, but is usually accompanied by other symptons. Long shot. Check for a partially blocked exhaust pipe after the cat. You know, crimped or bent. Tod

Vronsky · #9 08-12-2003, 05:02 AM

Do you legally need a cat on a car of that age?
In Europe, cars before 1993 don't need a cat, although they do have to comply with some CO-emission level.
My MB is now catless: much better...

standard125r · #10 08-12-2003, 07:39 AM

Exhaust gas smells fine, no blackness of the tailpipe,and the pipe is new from the header back. This suggestion came from the 190 Revolution site... The trans mount might be bad. When I pushed up on the trans mount the trans visablely moved. One of the guys over there said that this actually caused his pipe to crack where the cat would have been. My local dealership does not have a five gas, and most of the shops don't either. We don't have emission checks here... yet. However the car is to loud with out the cat and taking it off is still tampering.

stevebfl · #11 08-12-2003, 08:10 AM

There is no need or use for a gas analyser on that car with a functioning fuel control system and working cat. Nothing will be coming out the rear anyway in those conditions.

The system is designed to allow monitoring and control evaluation from the diagnostic connector. Proper mixture is easily achieved and closed loop function monitored there. IT IS the first place to go. if you are running in closed loop and have this problem things might get tricky, but it is my guess that you AREN'T running in closed loop....thus mixture adjustment is not the first problem.

If that doesn't make sense, look up closed loop control in the archives. It forms the basis for all modern engine control systems.

ericnguyen · #12 08-12-2003, 09:20 PM

Dear Vronsky:

Do not compare your Europe with the US. We have a lot more cars here than in Europe, and the US emission laws (especially California) are very strict. For example, in California, very old gasoline cars (before 1973) as well as diesel cars are exempt from smog check. However, all newer gasoline cars (after 1974) are rigorously subject to smog check, so any gasoline car without a catalytic converter is sure to be rejected immediately. In the next October, California will introduce Smog Check II, which requires gasoline cars to pass some extra threadmill-like dyno test while undergoing other regular smog check procedures. It's estimated that Smog Check II will cause an additional 30% gasoline cars to fail emission tests.

I had to dump (sell) all my old gasoline cars (barely passing smog check) and buy only diesel cars so that I would no longer be on the edge because of smog check schedules.

California has about 33 million people, but there are 29.6 million registered cars here!

Best regards,

Eric

ericnguyen · #13 08-12-2003, 09:33 PM

Dear Vronsky:

Are you a brain surgeon? That's amazing!

BTW, in the US, the average salary of brain surgeons are about US$550,000 per year and many of them even make more than US$1 Million per year.

US doctors are aweful money suckers. I've read that some brain surgery procedures cost about US$150,000 in the US while they cost about $15,000 in Australia and some European countries. That's 10x less!

Each time I've received my medical and dental bills, I want to get fainted (even though the insurance covers a large portion). America is a country of super rich and super poor people. We do have plenty of homeless people on the streets, and our government keeps spending ridiculously huge amounts of money to "emancipate" other nations while letting their people kill young soldiers every day :-(

Best regards,

Eric

don_xvi · #14 08-13-2003, 08:37 AM

Ooh, can I make a social commentary, too?

Or should I just talk about fixing catalytic convertors?

#15 08-13-2003, 09:02 AM

Right on Eric...