'Empty' cat: louder noise?

[Vronsky]

At speeds over 80 mph, I notice that the noise of the engine/exhaust gets much louder. Since the cat is nearly 12 years old, I suspect that the cat is now an empty sh*ll
only (all catalyst material gone). Could this 'empty' cat cause this loud noise?

Cheers!

 

[Matt Crooke]

If the cat has lost all its innards then all you are gonna have is the empty sh*ll
. Hence i would imagine at a certain engine speed the sound is gonna resonate quite a bit. Have the exhaust checked out to see whats what

 

[Arnie]

Hi,

I don't think you'd be left with an empty sh*ll
as the catalyst material is normally deposited on a ceramic core. The material will wear out of course, but you'd still have the core. The resonance is probably a result of internal corrosion causing the internal bits to come loose.

 

[Vronsky]

Before the W124, I had a Ford Sierra. When it was about 10 years old, the cat suddenly started leaking, and when I had it renewed, it turned out that all content ('guts') had disappeard... Strangely enough, the car had passed the MOT a couple of months before.

Only recently I discovered that cats on cars of that age are not obligatory, and even are not necessary to meet MOT emission specs. Did cost me a lot of money though, could have changed the cat with a standard front price for a fraction of the cost. Plan to do the same now on the MB: very likely will pass MOT aswell.

Cheers!

 

[mrgeoff]

The Catalyst substrate is quite fragile, and "sometimes" they do break, but quite often the retaining material gets worn away by the gas, and then the brick rattles around, and finally breaks down.

A car will be slightly noisyer without the cat brick, but at ALL speeds. It would be most noticeable at low speed however.

You probably have something else loose.

 

[Stewart Smith]

In a similar vein - Mine is starting to sound 'throaty' under acceleration - Fine on Tickover. Took back box/centre box combined section off today and they look ok - no holes. Anyone else had a C180/C200 exhaust break down internally?

 

[Andy]

Hi Stewart

Try giving the cat a thump and see if you can hear anything rattling.


Regards

Andy @ www.mercedesservicing.com

 

[Stewart Smith]

Oh god not the cat.......
Will have a thump and check.

 

[john]

Always start at the beginning. As Andy says-give it  a dunt. See what happe ns. Might be a loose nut resonating. Tighten it. Job done - free. Might be needs replace a nut or bolt. Jobdone - costs a euro! might need a bracket or some other small piece - jobdone for a few euros. Only when all other avenues (cheap avenues) are exhausted do you consider a new cat.

Mercedes generally build cars to go bit longer than 12 years.

Hope this gives you a little confidence to get under the car.

 

[Stewart Smith]

All avenues to be explored before Cat! Yup.
It definitely sound exhausty, but it's not serious so I'll live with it.  - Might just be a loose baffle.
I found a reference to a recall notice for certain C-classes around my year saying the back section was replaced with stainless, which mine certainly isn't. Anyone got any details of that recall?

 

[Koolvin]

my cat's guts are ratteling as well so to speak - it happened a day before MOT but it still pased because the emmissions are ok and its not about to fall of etc etc...

The guy said if I could live it then it might last 2 months maybee a year and the ratteling would get louder etc - I was like 'mate, for 700 pounds I can put up with any noise - windows up stereo on'

 

[Koolvin]

oh ang my car has only done 47K

must be the short stop start journey's nah it must be MB pants quality cats..... might as well go for a cheap aftermarket one I suppose - ughhhh - nah... might as well get a second hand one :sigh: F it - i'll get a new one!

 

[Stewart Smith]

I can live with it for a while but if the fuel guage turns out to be a genuine problem at the next fill up I've had enough of Mercs.
Back to cheap reliable vauxhalls - maybe a 3 litre Omega and a few holidays in the sun with the savings.