I have a 1998 C280 MB that has a LOUD rattling noise near the center bottom of car when idling at low RPMs. I have narrowed it down to the exhaust system. I have what appears to be two small catalytic convertors where the exhaust comes off the two header pipes. The noise seems to be in one or both of the convertors. I can rap on them with my hand and "near duplicate" the rattle. The rattle almost sounds like a loose hanger bracket, but all of the mounting assemblies are very secure. The catalytic assembly appears to be bolt-on with welded pipes fore and aft. I noticed that FastLane appears to not carry any of the exhaust system parts. Is this something I can only get from MB? I would like to keep her 100% original, but I feel this is going to cost me an arm and a leg, even with ME doing the labor.

Any thoughts on the least expensive way out of this?

Thanks again, guys!

Curt

How many miles on the car? MB emissions/EPA warranty covers cat.s (i think) for 8 yr / 80k miles. Check your owners manual for confimation though. If not, check out perfromanceproducts.com They carry exhaust parts for the older benzs I know, they may also carry it for the newer models. You can order a catalog for free, I recommend doing that.

She's got over 120K, so -no go- on the warranty! I do appreciate the info, tho! I will check out the website.



Later.....
I checked the www.************************ site, but they show separate converters for the 98 C280. Mine is one all welded assembly with 2 small converters with pipes fore and aft.

I'm having the same problem with my 98 e320. After the car is warm, in gear and with foot on the brake (like at a drive through window) the rattle resonates off the side of the building. It sounds terrible. I think some stuff must break loose in the cats. (Damn those things). It's obscene that a car of this supposed quality has this kind of problem. I have 104K, so I'm out of warranty too. I'm going to my independent mechanic for his opinion this week. Maybe I can share some more favorable news with you by the middle of next week. In the meantime, if you hear of a fix, please post it. (I've thought about cutting the cats and/or the muffler(s) open, shaking out the loose crap, and having them rewelded closed). Fastlane-cats-$560 (x2), muffler, $470. Ouch!

Dave M

That is EXACTLY the mode that my noise is loudest at! It is progressively getting LOUDER! It's so loud today that I am embarressed to even stop at a stop light now! I jacked my C280 up this morning, put a screw driver to each cat, placed an ear against the handle and then (as we say in Texas) "whomped" the cat with my hand. By this old method, I determined that the cat closest to the driver's side is the loose culprit. Of course, with the 98 C280, you have to buy the WHOLE assembly which includes both cats. About $440 is the cheapest quote I can get, as yet.

I found a rubber mallet to be the best tool for finding cat rattles.

Mike

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

With my bad knees, it was too far to crawl out from under the car to get my rubber hammer. I just used what I had under there with me. Since both cats are mounted together, if you hit one, they BOTH vibrate, so using the screwdriver as a stethoscope remedied the troubleshooting problem.

Anyone find an inexpensive source for those stainless steel cat assemblies for the '98 C280? I really don't want to start cutting them up and then welding new parts together. Would rather keep it close to original.

These guys have good prices:

http://www.ecatalyticconverter.com

I have not done business with them however. They claim to sell DEC. I would avoid Catco. IMHO.

Mike

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

Mike is right. ecat.......com beat Fastlane's prices, so far, (for my e320) by about a 100 bucks, each cat. But, they also recommend replacing the 02 sensors (I would need 4 @ $103 each) whenever replacing the cats. I've yet to buy anything as the car is going in for service (and opinion) tomorrow. I guess I'll know more then, even though I'm preparing for the worst after some preliminary discussion with one of the techs kinda points to the cat(s) being toast. And, like you, I don't know whether this old body can take crawling around under this car to do an exhaust system job. I gotta say, I've just about had it with this benz. My '88 S-10, that never gets any attention, (periodic oil changes, never bathed, beat-up, stinky, and rusty, and pretty much just a dog hauler and drag my sorry ass to work) for the past 6 years, hasn't treated me as bad as the benz (personally or monetarily). I wonder if you could disconnect the mufflers and then just ream all the crap out of the cats? Just a desparate thought.

Dave M

A long shot, but in my case, a similar noise, was caused by worn-out engine mounts. At idle, my catalytic convertor was vibrating in tune with engine vibration. Replacing my motor mounts fixed my noisy cat problem.

Check your engine mounts first. You have nothing to loose.

Phil

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'95 E300 Diesel, 264,000 Miles. [Sold it]

Curt,
I took my e320 to my mechanic, as I stated in an earlier post, and here is what I learned. At least on my "e-class", the parts I thought were the catalytic converters are actually resonators. The cats are farther up the line toward the headers. While this does not mean the cat(s) aren't bad, it does mean the noise is in the resonators. It could be that there is cat converter debris in the resonator(s), OR, it could mean a loose baffle in the resonator itself. I'm hoping for the latter, of course. So, the plan is to cut open the resonator (with a plasma torch) and see what's what. He indicated that the right resonator was the suspect. If cat converter honeycomb falls out, I guess I'll know I've got a cat going bad. If a baffle in the resonator is loose, it could be tack welded or removed. He said he could weld a sleeve (by the way, the sleeve is a BENZ part) over the baffle where the initial section was removed. The best part (if all this works as planned) is we're talking about 150 bucks, parts and labor. Either way, the rattle should be solved (temporarily if it's cat material that falls out after the surgery...time to sell, or permanently if it's a baffle or sheet metal). Our circumstances really sound similar, and while I don't know anything about a "c-class", I hope this info helps you, and hope you have a mechanic or a tech who is willing to do this work. I guess the cut could be made in the resonator with a cutting wheel on a 4" grinder instead of a torch.
The last thing I can tell you is, my mechanic is probably the best I've ever seen with european cars. I really trust this guy. Maybe the last thing I should say is, he kept the car, so I won't have a final verdict until tomorrow. I can keep you posted if you want. I'm hoping for the best....for both of us.

Dave

Curt,
The e320 is still in the shop. As it turns out, there are four (4) cats on my car. The two my mechanic said were resonators are in fact secondary catalytic converters. However, as he continued to explain, they are not "monitored" by the engine management system (02 sensors). On my car, the noise is coming from the right secondary catalytic converter. While pieces of the honeycomb in this cat have not broken off, the cat itself has separated from its sheet metal canister and is rattling against the sides of this housing. He cut the defective part out of the system and has ordered a part out of Cleveland, OH that he says is of identical composition of the defective cat and he will be able to adapt it to the system. I ask him about just knocking the honeycomb material out of the defective cat and welding the empty can back up into the exhaust system.
I don't think he can legally do this (but you or I might be able to). He said knocking out the honeycomb would be a long tedious process (6-8 hours). I guess it might also be possible to carefully cut the cannister open and let the honeycomb fall out in one piece and then re-weld the cannister shut, leaving an empty cat in the system.
Now, with the new part he is installing, I'm looking at 250 bucks, parts and labor. When we talked about after market catalytic converters, he said they have about a 50% failure rate (and the cheapest ones I've found are $350+). So, you can take this info for what it's worth. Sorry about the previous post with the eroneous information (I was disappointed, too). Good luck with your "C".

Dave