Mine was rattling similar to bad alternator bearing. Took me a while to diagnose that by removing the belt.
Overheating converter also change the color.

 

A sulphur like smell coming from the exhaust and/or rattles from the CATs indicate bad or worn out Cats. Also an exhaust noise that sounds like the exhaust is clogged up.

 

Hello everyone! Can someone post a list of symtoms of bad cats? I think my cats are bad because I hear a low groan when I accelerate from the bottom of the ml430 2000 with 98000 miles on it and also its been running sluggish lately. The groan is there too when Im parked and revving the car.

had the same symptoms. it was a cracked cat.

 

had the same symptoms. it was a cracked cat.

What is the warranty ( maximum miles) on the cats????

 

My manual says 7-years, 70,000, but I heard that they've been some recalls that even extended that. Call your SA to check.

 

Ours sounded as if it had an exhaust leak. Turns out the converter split open so it was leaking.

bill

 

I called MBUSA and a local dealer, they stated that it's was bumped up to 80,000 miles.

That was really nothing if you ask me.

Rico

 

cracked cat

had the same symptoms. it was a cracked cat.

Hi roadsession! Hows it going? So do when you say your cats were cracked does that mean I could get them welded? Or r u saying your cat was on crack?

 

Thank you

 

melted cat will reduce your engine output severely. worn cat will rattle.

 

more cats

When the cats rattle, does the rattling noise sound like they come from the
front ?

Also, do they rattle mostly during lead foot driving ?

I heard a rattling sound when speeding up past a slow coach A6. Can it caused by a loose shield ?

Thanks

 

Hello everyone! Can someone post a list of symtoms of bad cats? I think my cats are bad because I hear a low groan when I accelerate from the bottom of the ml430 2000 with 98000 miles on it and also its been running sluggish lately. The groan is there too when Im parked and revving the car.

I had mine replaced by the dealer. The ML had 110000miles on the OD at the time. This was done under the Catalytic convertor recall. I would call MB USA directly to se if yours is covered.

 

I am green on this subject

I had mine replaced by the dealer. The ML had 110000miles on the OD at the time. This was done under the Catalytic convertor recall. I would call MB USA directly to se if yours is covered.

What is the general recommendation for determining if they are in fact clogged and zaping power? I assume that a full cost replacement of the four cats would be quite expensive! My SA checked them about 20K miles ago and said they were fine under the recall program (not cracked). I have 114K miles on my '99 430. I will probably own it for just one more year and I know I won't get my $$$ back even on a private sale but I also want to enjoy the full power for the next 12 months. I know they are not cracked but I cannot determine if they are clogged. Will I be able tell a difference on new cats if mine have only normal build up?

 

What is the general recommendation for determining if they are in fact clogged and zaping power? I assume that a full cost replacement of the four cats would be quite expensive! My SA checked them about 20K miles ago and said they were fine under the recall program (not cracked). I have 114K miles on my '99 430. I will probably own it for just one more year and I know I won't get my $$$ back even on a private sale but I also want to enjoy the full power for the next 12 months. I know they are not cracked but I cannot determine if they are clogged. Will I be able tell a difference on new cats if mine have only normal build up?

LOCHS,

If your ML is running fine, dont replace the cats. I believe you can test it by driving up a steep hill, if you can climb it doing 80 without downshifting then do not replace the cats. If you have to downshift all the way to 3 just to climb that hill then your cats may be fouled or clogged.

 

Interesting

LOCHS,

If your ML is running fine, dont replace the cats. I believe you can test it by driving up a steep hill, if you can climb it doing 80 without downshifting then do not replace the cats. If you have to downshift all the way to 3 just to climb that hill then your cats may be fouled or clogged.

I never thought of that. of course I live in flat plains illinois but I could always try a draw bridge over the Chicago river and jump to the other side. lol

 

Id like to see that! Take pics of that jump ok.

 

lol

Id like to see that! Take pics of that jump ok.

That would make the news for sure! We had a cold front move through here and I was running through the gears on the Reagan memorial toll road and I think I am fine. Surely free flow cats would be better but I think the problem has been the summer heat (90s) and having the A/C on full blast. That is zapping the kompressor more than semi-clogged cats.

I asked you about the noise because I already have a supersprint muffler with a nice groan and if I do the free flows I was wondering about being too loud and perhaps insufficent back pressure as well. At some point I want to get $7K-10K in a trade-in and if it is too loud it will turn off a few customers...