Hey,

First I feel it necessary to throw out a caveat. I just bought my first Mercedes two months ago. In other words, if it sounds like I don't know what I'm talking about, it's because I don't. Anyways...So I noticed a rattling sound the other day... turns out the inside of by catalytic converter has come loose and is rattling around inside. I later learned that there is 4 cats and that it is the biggest (apparently it's like a double) that is broken. I called my local M-B dealer and they said I have to replace the whole system from the Manifold back and it's gonna be $1600.

What are my other options. Obviously I need to replace it. But can I buy just the Cat? If so, where? How much would it cost? If I have to buy the whole system, what are some reliable and relatively cheap websites that I can buy from?

Any help that anyone could lend would be greatly appreciated

Thanks!

 

Hi,
Rattling doesn't mean that the catalyst isn't / doesn't work.

However if the "brick" is loose because the material that supports it has "disappeared" (Common MB / cat problem) then as the brick rattles around it MAY eventually breakup into small pieces which COULD block the exhaust and create problem like the CEL Check Engine light coming on.

MB cats are a unique shape and only available thru MB.

The front cats near the engine do most of the work. They give less trouble because than the ones mounted by the gearbox aince they are mounted nearer to vertical and are less prone to water cooling etc.

MB are correct that on the M112 320V6 one down pipe (manifold) has 3 cats on it and the other one just one. Maybe you are luckly and its on the "one" side. BTW No need to change system rearwards of the gearbox mounted cats.

Aftermarket replacements are available but require you toe splice (clamp/weld) into the pipes. They work but can give problems especially strange tinkling sounds etc in the exhaust note.

Dependent upon where you live in the States you may find no real ill effect for many thousands of miles. As the cat degrades you MAY find passing the smog test in California is a problem.

Some posters have identified that cats are warranted for at least to 100k miles in the States. I don't know about this since I live in the UK but I suspect there may be a caviat..i.e. .IF they fail to meet the required Smog laws. I suspect grounding damage, water cross spray, wading etc...all the excuses that MB use...MAY preclude replacement purely on noise grounds.

Good luck.

Stuart

 

im pretty sure alot of states cover emissions under 8/80 which is 8 years/80k miles

 

I believe mbtech17 is correct; his postisa paraphrase of the Emissions System Warranty language in theMB Service and Maintenance Booklet.

StellaGirl, if you don't have this booklet, theMB Dealer does.That said, the Warranty appears to kick in when thecatalyticconvertor, and/or orther covered items in the warranty, fail as opposed to failing, whichit reads like is happening to yours.
If it were my car, I'd beback at the Dealer with the Service Advisor/Service Managertrying to make the casefor an accomodation replacement of the failing Cat as it appears to be only a matter of time until it does fail.Obviously if they want to charge you the small fortune to pay to replace it, it must be failing or why replace it? The Dealer can't haveit both ways.

Prior to meeting with the dealer, you may want to get a 2nd opinionon the 'health' of this Cat Convertor from a qualified independent shop with MB trained/knowledgeable techs. If they too recommend replacement, get their quote in writing.

Bob

 

im the lead mercedes tech at our dealership and we replace noisey cat. converters all the time under 8/80 for noise concerns-M.B. got smart and released a Cat converter noise analysis that runs through the SDS in which that printout is required to be returned with the noisey converter-i would definately make a statement about this to your dealership

 

I'm interested in this due to MB UK's position on this subject. Was 1 year. Now 3 years.

So how does your dealer respond when you request it is changed under "8/80"?

Stuart.

 

It is U.S. Federal that ALL Catalytic Converters are 8 years or 80K miles...

take care,
-mar-

 

Yes but... "Rattling" doesn't mean that the cat will fail the emissions requirement. the law requires that the emission parts continue to meet emission regulations.

So will MB USA change the cat FOC (i.e. for FREE?) irrespective of why the cat needs replacing. i.e. Grounding damage? Rattle? Wading?

Just interested. Stuart.

 

YES your right! However, MB knows that this a common problem, and they should replace it for no charge. Another thing to do is...take your car to get an emissions done (that's if your state requires it). If it fails then you can submit a claim. When I worked at the MB dealership, MBUSA never had a problem replacing CATs that were under 8/80. My suggestion to you is ask the dealership to see if it's still covered.

take care,
-mar-

 

You are quite correct. this is a common and VERY expensive fault. StellaGirl is based in the USA so should try and see what happens when she submits the vehicle to an MB dealership. Warranty is managed by MBUSA and MAY cover matters.

I was interested because the exact same installation and engine tune used to be only covered for 1 year in the UK but has since been increased to 3 (to stay competitive with other manufacturers in the UK) BUT the exceptions I have stated remain a sore point.

MBUK of course state that the UK is a different market, with different spec cars but what they really mean is with a "different perspective on litigation". Common (safety related) failings like the SLK Brake light (Recall in the USA) are not so handled in the UK due to litigation being less prevalent in the UK. Basically MB try to, and in general terms succeed, in getting away without paying. The UK MOT test which starts at 3 years doesn't put the responsibility for non compliance on emission related issues on the manufacturer but the owner to ensure the car complies!

C'est la vie.