My 2003 S430 4Matic started to rattle from the center of the vehicle, so I brought my vehicle to mechanic to double check on the cats. For sure enough, it was for both rear cats gone bad. Quote? $1800 for OEM cats(with the piping).
No way I am spending that, so I asked my mechanic with other options.
Here is what I have done on mine.

Original pipe diameter: 2.25 inlet/outlet
cats I ordered: Magnaflow Part#53004 (2in inlet/outlet). I ordered one size down, so the OEM pipe goes over the cat pipes and easier to weld and fill in the gaps. If you want to order 2.25 inlet/outlet cats, part# is 53005. Cost is $63.27 free shipping from
http://www.planetmagnaflow.com/shop/...53004-650.html

Cats came in 3days and I brought to my mechanic to cut and weld. $100.00
Total cost for replacing cats: 226.54.

My mechanic also was telling me that the front cats rarely goes bad and it is PITA to replace those due to the location and offset.

 

Mine were rattling, and I had them removed and straight pipe installed in place. Total cost = $30.

Exhaust sounds exactly the same, minus the rattle!

 

How do you go through inspection (smog, emissions, etc.)?

 

 

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Wait, on a 2003 the cats are covered by the FEDERAL 8yr 80k mile warranty. I assume you took this to an indy instead of MB?

If you have more than 80k miles Theres also a 10yr unlimited mile extended warranty on many w220 cats, not sure if it applies to your car.

I sure hoped you checked with the dealer first.

 

That only applies to certain VIN S500 series, not every S class. Mine has 103k mi, so I was SOL on both counts anyway.

Straight pipe is good idea, but Illinois has inspection every two years, so I cannot delete the cats.

 

Im selling cats for $1000 thats both shipped let me no 50k miles

 

You want $1000 for used cats? Ones which may be recalled anyway?

 

No emissions testing or inspection in my state

 

if you cut the cats dont you get the check engine light on?

 

Your check engine light will not come on if you take off the back 2 catalytic converters. There is a total of 4 converters on the car. This is the sequence: 2 front converters, o2 censor, then the second converters. If you take out the back two then the o2 sensor will not be affected and your check engine light wont turn on. If you take out the front one then the check engine light will turn on. I am not 100% on this but this is what i experieced on my car.

 

so lets say if i do have that rattling/grinding noise coming from the cats, it could be from either the front 2 or the rear 2 and if i cut off the back 2, the noise miiiiiight not be gone?

 

Hi AdrianX,

I have the same issue too with the CAT converters on my 2003 S500. My mechanic still has to diagnose which ones are bad but recommended that I change to refurbished ones from MB Dealership which will still come up to 1800. He mentioned that the aftermarket ones are no good and go bust in 6 months or so. He is a Certified EX-MB foreman. I was looking at your post and wanted to know if you have had any issues at all by now? Please let me know asap as I have to make a decision. Appreciate all your input. Nice post BTW.

 

I put on 2 aftermarket cat. converters and they're still performing fine today after 15000 miles.

 

You can get the magnaflow for $60 so I don't know why you'd get OEM mb for $1800?

 

Our cars are nice drivers. Personally I can see no value in OEM parts for an issue such as cat. converters. The difference between 1800 and 200 including labor is staggering.

 

Hi Tusabes, I agree with you. Just yesterday I went to another MB technician and he said the right side converter needs to be replaced. I asked him front or back he said "Right side" .. Quote is $940 All inclusive with a refurbished part from MB dealer. I will still need to determine of the front or back is bad before I buy either the refurbished or Magnaflow part. I prefer the magnaflow $60 part.

 

Mrbobby,
I'll second that.. Smoke flows faster than money thru it !!!! So we'll let it. ;-)

 

Hey guys. I can hear the same rattling sound from the bottom centre of my car. It is a 2004 S350 which i bought used 5 months ago. I guess its the cats going bad. Will it cause any harm to my car if i drive around with this rattling? till i get it fixed that is.

Thank you

 

Its fine

 

Thank you Tusabes

 

Thanks for the write up. I'm experiencing the same problem, but unfortunately I'm located in CA. Because I'm in CA, I need to order Magnaflow part number 451205, which is almost exactly the same as part number 53005, but costs an extra $150 more per cat. Anybody in CA find a cheaper solution?

 

The only problem with aftermarket vs OEM is one of quality issues if you get it wrong.
Sure you can by cheaper than OEM but make sure quality is not the trade off.
The precious metals used in the cats is what pushes the price up. The really cheap units have little in the way of precious metals, and Mercs have very low thresholds when it comes to emmisions.
We changed out the wifes Lupo Cat for £300 vs OEM's £1000 and after 18 months the engine management light started to come on.
Easy re set with a code reader and it only pops up once every 6 months or so.
But the VW tech did say it doesnt happen with OEM units only aftermarket.
IMHO its no big deal considering the price difference, but something worth keeping in mind.

 

Where in CA are you ? Asian muffler shops tend to have the lowest prices , about $180 installed . You won't get a name brand but it will be CA legal to pass smog

 

I'm starting to hear a rattle as well but it seems to be coming from the front. Is there a test you can do?