Mercedes C240 Catalytic Converter Noise

[@dillonedwards7075]

My C240 makes the exact same noise. It has been doing it for 2 years now and I haven't had a problem with it.

[@dpark76]

Daniel, It was the honeycomb structure inside the catalytic converter and had to be replaced. On the C240, there are 2 catalytic converters and they are slightly different. If I recall correctly, we had to replace the slightly more expensive one.

[@cletusrodgers1547]

dpark76 there are 4 cats on the c240. 2 upstream, 2 downstream. The exhaust goes from two pipes to one that connect to the muffler.

[@gankeowan]

when attempting to diagnose a vehicle fault/condition, always helps to provide the year and mileage of the vehicle.

[@chrisarmes17]

regarding your rattling. the honeycomb part that is rattling is your emissions controller inside the converter that has come loose. you can take to a local shop and have them blow torch open the catalytic converter for a few hundred bucks take it out and no more noise.

[@anawobass5382]

Never do that, your exhaust smell will be so bad and it harmful it cause cancer to the people surrounding the Car after years, better to find used cat and replace the old one

[@dpark76]

if it's the catalytic converter you may want to get it checked out because hot chunks can pass down into the muffler and ruin that. It could also create problems for passing emissions testing too. Please be sure to reply back here if you ever have problems with your CC or find out if it's another problem. Thanks.

[@rungsat1]

The rattling sound under the hood is the ac compressor bearing about to go. I know because mine went and violently shot the faceplate and ball bearings out from the compressor . There is a serpentine belt that is for cars "without AC" which is short enough not to reach the AC but is routed exactly the same

[@hunter7925]

When my e320 is really cold it make the most strangest sound ever, puke something rubbing up against something, but when it warms up you can't hear it any ideas??

[@martyG861]

Did you find out what is the noise around the winshiled reservoir mine is doing the same clicking noise ?

[@andresbaron5189]

Thats normal, mine does that as well, its from the electrical wiring

[@topdoginc9400]

It’s actually you power steering electric system letting you know it’s in working condition and it stops after ticking for some long

[@martinhuusfelt1783]

Was it constant from cold? My E55 AMG w211 just started same out if the blue but only when is hot else silence is so strange sound like a broken rod

[@anawobass5382]

The same my S55 you need to replace it by used cat from junk yard but you need to know which cat damaged as you have 4 cats in the car

[@dylanwaller8968]

I have the same noise on my w204 c300. It’s only when I cold start the car and when it’s not moving as well. It goes away after some driving though.

[@rontruocchio5744]

i've had cars where the upstream cats broke down and the broken material went through the pipes and clogged the lower cat completely

[@ryndavis485]

My C320 has this rattle in it but only while the cars warming up, after that it drives nice and fine

[@mafia7976]

I have the same problem how much does it cost ?

[@danielcardona6996]

did you find the problem of the noise?

[@joshgray2024]

Lol thank god. Im like wtf is this on my 430 today lol. Cat hot as shit

[@ishmam87]

I have this same problem with my 2005 C230K. Mercedes said it would cost about $1700.00 to fix, which includes labor. Ridiculous! But they did say that it will not harm the car. It just makes an annoying rattling sound.

[@frankmtz2010]

Sorry Just have to ask so did you replace Cat ? And did it fix the Ratliff noise

[@dpark76]

yes. see my comment to daniel.

[@dpark76]

yes. see my comment to daniel.

[@dpark76]

yes. see my comment to daniel.

[@azbarak92]

I think it's need buy new mount to stop noise

[@zuki6146]

how much was the cost of the one you had to change?

[@stillridin9600]

The c class will eventually give up and have dead cylinders buh bye new engine required

[@n71itrer]

You just don't get much out of a car these days!

[@ROSSYDAVIS]

Clutch