Exhaust ratle

Page may contain affiliate links. Please see terms for details.

Ian Topping

Active Member
Joined
Apr 1, 2008
Messages
97
Location
N. Ireland
Car
CLK 55 AMG
My CLK 55 has a rattle under the passenger side front seat or there abouts. I am told it is a cat converter that can be removed and left out.
I initially thought it was a heat shield, but when you tap the mid box you hear the rattle. The CLK exhaust system splits at this point under the car and goes into 2 boxes with Cats, before going on down the car to the back boxes.

Has anybody else experienced this rattle, or removed cats with no ongoing issues, such as turning the engine light on, or failing the MOT?
 
Seen this first hand on V engine mercs. They break up and rattle around in their housings. Realistically they won't be doing their job and if anything will cause a restriction and lack of power. Would
Imagine you would get away with removing the inards without affecting emissions or an EML. Would of thought it would of put the EML on already if it was monitored by O2 sensors!
 
I don't think they pose any more of a restriction if the monolith becomes detached; it's still a huge surface area to pass the gas over.

With respect to the MOT, as long as emissions pass it's a case of "no harm, no foul"... unless you get a pedantic tester who recognises a cat is missing and fails it for defective emission control.

As above, there's no issue with the engine management light because they're downstream of the lambda sensor. - The only probe they might have is a temperature probe to warn you if they're red hot and good set long grass on fire..
 
Many thanks guys, I appreciate your feedback. I will get them removed and let you know how it goes. They hope to open the pipe and take the bits out without having to cut open the box and then weld shut again, which could draw the attention of a pedantic tester.

Will it make the exhaust louder, with the Cats removed?
 
I decatted a car once by removing the cat and then shoving a bar down it, smashing the cat up and it just pours out as fine goldy powder.

In your case it's probably just a couple of chunks that have broken off, you could just tip them out if you didn't want to gut converter, but there's no need to cut it open, the matrix is extremely brittle.

Will it make the exhaust louder, with the Cats removed?

With them gutted, it'll be slightly louder, but not a huge amount as the fatter, now hollow area still acts as a low pressure zone like a backbox and silences to some degree. It'd be quite a bit louder if you were to replace the cat section with a straight pipe.
 
Having completely removed the cat from my Nissan, it is definitely louder without them; so much so that I took the straight pipe decat out, and put a silencer in it's place. - In that cast it was perfectly legal since it pre-dates any requirement to have one.

If you can find a silenced decat that fits the space, that's a better option than destroying a catalytic convertor (since they are actually quite expensive items). - It looks a lot like it should be there, so if you don't look too closely you might be fooled into thinking it's a "sports cat" or similar.

There are companies that will recover the precious metals and recycle the innards if you do decide to destroy the monolith (usually cordierite for petrol engines).
 
Cheers Guys, I really appreciate hearing your experiences. I will remove the cats and let you know how it went. I hope to get a bit more power but not too much noise :)
 
Local Tyre garage suggested blowing out the broken pieces, so I decided to give the car a good old charge and it seems to have blown the rattle away quite literally.
 
My recent exhaust rattle turned out to be a broken bracket, cheap weld to fix.
 

Users who are viewing this thread

Back
Top Bottom