cat question W208 CLK320

[SteveX]

Hi,

I'm planning on replacing my secondary cats, however I'm a little confused as to the layout.

I thought that the right section actually comes with three cats, one primary joining the manifold and two in the center, however I have seen some with just a longer pipe joining the manifold on the right and no primary cat then two in the middle such as this:

http://www.ebay.co.uk/itm/Mercedes-...arts_Vehicles_CarParts_SM&hash=item2ec33591ff

Can anyone tell me what the set up is on my car?

Also I don't want to open a can of worms, but I read some threads on here about actually removing the secondaries as they are not needed and were initially there for stricter regs in other areas of the EU.

I've also read a lot about 'blocked' cats and them damaging the engine, I've never heard of or seen a blocked cat, I've seen noisey ones but never any engine damage. What do people consider a 'blocked cat' surely if there was a problem with the capacity / flow of the cat it would throw an error.

Thanks,

 

[bigasotonuk]

Hi,
As far as I,m aware the O/S front part of the exhaust has three of the four CATs and the N/S front has only the primary of the N/S, this is how it is manufactured from MB. I have never seen a CAT equipped V6 or V8 engined car that does,nt have four CATs. How many CATs as yours got at present?
The one in the e-bay auction is clearly missing the N/S front pipe which would have the CAT fitted, though the O/S does,nt appear to have a CAT fitted at all.
To be honest I would,nt even bother about replacing the secondary CATs, the car will pass the emissions without them so just leave them there unless of course they are rattling then just get them taken off and then drive a hefty steel pipe into the pipe to shatter the CAT internals, leaving a straight through pipe.
Have a look in the link this should be your exhaust configuration.
http://www.neoriginal.ru/cat/mb/part_202033_1_1_45Y_208_465_/49_210

 

[SteveX]

Thanks very much, the link you posted is exactly what I expected. When I saw that used item on ebay (simply when searching for the exhaust lay out) I found it very, very odd that one of the primaries would be missing, this would lead to two cats on one side and only one on the other.

My car I believe has four cats, although I have been underneath and seen the two secondaries, I have not actually looked for the two primaries under the back of the belly pan yet.

Regarding removing the secondaries, does this make the sound noisey? If they are not needed then I may remove, but I do not want it to make the car louder.

Many thanks.

 

[bigasotonuk]

I would just leave them alone if there not rattling. Not sure whether they would make a lot of difference noise wise with them removed, I have completly removed both my secondary CATs and middle box on my C43/55 and thats is quite loud Like I said if you want them removed just smash the insides out and put them back on.

 

[SteveX]

I would just leave them alone if there not rattling. Not sure whether they would make a lot of difference noise wise with them removed, I have completly removed both my secondary CATs and middle box on my C43/55 and thats is quite loud Like I said if you want them removed just smash the insides out and put them back on.

Thanks again, they are making a low pitched clonking / vibrating type noise rather than a metalic rattle, and only at tick over.

 

[bigasotonuk]

Are sure that is the CATs and not the heat shields fitted on the exhaust and the body? to me this would sound more feasible than the CATs being at fault.

 

[SteveX]

Are sure that is the CATs and not the heat shields fitted on the exhaust and the body? to me this would sound more feasible than the CATs being at fault.

Hmmm, that could be a possibility, I hadn't thought about that (things are never usually that simple for me ).

The cats actually looked in very good condition from the outside, but then, I appreciate that this would not be a clear indication that the inside is ok.

I'll get under the car later and give them a tap.


Cheers!

 

[Gkinghorn]

If the cats are breaking up it will sound like a tin can dragging on the ground - audible at low speeds .. A clunk sounds like something not fixed securely or a bolt shearing..

 

[SteveX]

If the cats are breaking up it will sound like a tin can dragging on the ground - audible at low speeds .. A clunk sounds like something not fixed securely or a bolt shearing..

Thanks, definitely not a high pitched metallic rattling or clanking sound, a dull kind of rattle, like I guess if you put something quite dense but soft like an orange in a tin can and shook it lightly from side to side.

It's coming from under the car near the secondary cat area, I haven't had chance to pop out and tale a look yet but will have a peek in a mo.


Cheers,

 

[Gkinghorn]

Dull rattle might fit the cat breaking up ... Pay someone a fiver to stick it on a ramp and see from underneath ..it's what I ended up doing to be sure mine were shot...

 

[SteveX]

Yup they are on their way out, got the car up wrapped a soft cloth around a mallet and gently knocked the cans of the cats, you can here them rattling around a bit. They aren't that noisy at all really.

Checked the heat shield and it's on fine, tapped all other areas of the exhaust and it's fine, just the secondary cats.

I was going to replace the whole section, but if it will still pass emissions and not be noisy with them gutted I may take them off and remove the innards. It's not actually very loud at all, you really have to listen on tickover and stick your head to the floor outside the car, so I'm not certain if it's essential to sort right now or not?

Have you guys ever heard of any negative impact on the cars running with a slightly noisy cat?

Cheers,

 

[Gkinghorn]

The only thing I have heard was that if the cat breaks up enough for bits and pieces of it to make its way I to the exhaust pipe itself it could conceivably block it.... If it does get blocked you will have major problems. A number of us on here , including me , have had them simply cut off and replaced with standard pipe work and they still pass MOT. others have simply opened the thing and took the innards out then resealed.

Go to a decent exhaust place and get it done would be my advice.... I had mine cut off and new pipe work put in for £100 cash in hand... Good as new....

 

[SteveX]

Spot on thanks

I guess it still runs fine and you get no errors from doing that?

Cheers!

 

[Gkinghorn]

No difference at all ... When you change the primaries I believe you may get sensor issues if not done correctly but for the secondaries this works fine..(at least on my R230 but others have done this with other models and similar results)