Rattly Catalyst- dangerous to engine?

Alps

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hi guys,

for abt 2 months now ive been driving with what i thought was some loose exhaust shielding under the car, so i finally got it up on a ramp and was told and shown that one of my cats was rattling, my mechanic(mate) told me i should replace as soon as poss as this will not only fail the MOT but they are known to spit pieces of cat into the engine and damage engine?!?!

what do you guys think, are they dangerous or am i ok to drive around with it rattling until i source a 2nd hand one? (new ones are extortionate, and id rather try to stick to a original MB one)
 

Satch

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I would not be too happy about fitting a second hand cat: how did such a thing come to be second hand in the first place and will the damn thing get past emissions tests? If from a crashed vehicle no barge pole is long enough.

Do not know how much you have been quoted, but this lot want £750 for a C36 cat.

http://sapmotorparts.com/?source=overture


You mayalso be delighted to know that there is an EU Directive on the subject as well:

http://www.dft.gov.uk/stellent/groups/dft_roads/documents/page/dft_roads_507965.hcsp

More taxpayers money down the drain.
 

Sp!ke

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Your Friend is indeed correct. There have indeed been reports of bits of the CAT being eaten by engines in the past.
 

Tan

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I think that my rattly noise is a similar problem, however MB never warned me of the dangers just that the shield/case was damaged, they were quoting in the region of £1000 for the parts alone
 

Sp!ke

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Tan said:
I think that my rattly noise is a similar problem, however MB never warned me of the dangers just that the shield/case was damaged, they were quoting in the region of £1000 for the parts alone

9 times out of ten it is the CAT shield that rattles - in which case, just just the shield off. They can disintegrate internally however which is what you need to be careful of.
 

Glideman

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The cat on mine has gone, just one side. I've done 10,000 mls & it's still the same. If you look under the car it's half way along the underside where the cat is, don't know how it could be drawn 6-7 foot back up the pipe & into the engine. The engine breaths out of the exaust not in.

I've been quoted £750 at the stealers. But seen none gen parts for as little as £200. In my experience patern parts are a load of crap & patern exhausts are noisy.
 
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Kinky

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Tan,

I had the baffles go on my Tiv - I dunno which noise was worse @ 06:00am every morning .... the throaty SS twin sports exhaust ....... or the baffles. They made an absolutely awful racket. Really peed off the neighbours !

K
 

Ian B Walker

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Thinks the RSPCA would have something to say about throwing a cat in the engine. :D Now who said I'll get my coat?
 
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Alps

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2nd hand cats are normally there cos the car has been written off, id rather pay £100 for a 2nd hand cat rather than pay MB £2324.04 + VAT for a new genuine one! ive heard bad reports abt aftermarket stuff for the AMG models, so im gonna try and stay clear of them unless i really do get stuck!

so if anyone knows of a written off C36 in their local scrappy, please could you let me know!

i`ll just have to drive it around and risk the engine thing until i find one!

thanks guys\gals
 

Satch

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Alps said:
2nd hand cats are normally there cos the car has been written off, id rather pay £100 for a 2nd hand cat rather than pay MB £2324.04 + VAT for a new genuine one!

Be careful. A catalytic converter is a a ceramic structure (or maybe beads in some cases) coated with a metal catalyst, usually platinum, rhodium and/or palladium. The idea is to create a structure that exposes the maximum surface area of catalyst to the exhaust gases. A modern "three way" cat usually contains two ceramic units, being a reduction catalyst and an oxidation catalyst.

"Ceramic" is the key word. So one of the great Cat. Killers for the ceramic matrix type is mechanical damage. Indeed, your rattle may be a lump of the ceramic substrate broken loose. A Cat. taken from a write off may well have suffered a mighty thump!

If you can source a seeemingly undamged Cat. fine, but I would suggest not paying (or at least have it agreed that a full refund was available) pending fitting followed by a performance & emission test.

Good luck
 

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I too have heard that particles of the CAT can be 'sucked' back into the engine, rather than continue to risk this and the subsequent damage, would it not be better to remove the cat and replace with a straight pipe or remove the cat and remove the insides and replace.

I got a universal CAT to put on my mates EVO6 that had no CAT at all, when it was taken for it's MOT they thought there was something wrong with their machine as the reading was so high. They failed it so we made up a new CAT and fitted it.

I'll make some enquiries.
 
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Alps

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thanks Jimmy,

only one of the 2 cats is rattling, so a replacement for the one cat would be a good option! although a bit of chopping and wwelding might be requied as both cats go into a center resonator box which is all one piece!

Satch, thanks for the advice, i`ll make sure i do that (might have to leave a deposit or sommin) all depends if i can find one!
 

Shude

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You might find that the C36 CAT is the same one used on a C280, see if you can compare some part numbers, might be a bit cheaper.
 

Satch

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rirhill said:
Alps whats the symptoms of a cat on the way out?

Thanks
Ian

Below is from a US website which covers blockages. However, the damn things will eventually give up and you will simply not get through an MoT exhaust gas test.

"The inside of a catalytic converter is made up of a honeycomb-type of material that can become restricted with soot from the engine exhaust. In some cases the material inside the converter can break apart and actually cause it to restrict itself. When this happens, you can usually hear a rattling noise coming from under the vehicle when you accelerate. I actually think it sounds like popcorn popping.

If the engine is performing correctly, there really should not be much soot or debris entering the exhaust system. An engine that is running rich (too much fuel) will produce visible black smoke and soot from the tailpipe. This soot will eventually plug up the honeycomb material inside the converter and cause a restriction, and this restriction will cause the lack of power complaint you are having. In this instance, the converter is a symptom of a poorly running engine, and is not the cause of the lack of power.

What can cause the engine to run rich and eventually plug up the converter or exhaust system? It could be an engine that is misfiring due to a bad spark plug, spark plug wire, or other tune up related item. The problem might also be a faulty engine control sensor or emissions control sensor that is not properly regulating the engine fuel and air ratio. Or you may have an engine that is "out of time" or having an ignition timing problem.

So now that we've covered the possible root causes of a restriction in the exhaust system, how can you tell if the converter or exhaust system is restricted? There are special testing tools that your mechanic can use to test the back pressure of the exhaust system, but there is also a simple test you can do at home to check for a restriction problem. With the vehicle in park and the engine running, quickly mash down and release the gas pedal to "goose it" while someone is standing next to the exhaust tailpipe. Caution: exhaust gases will be very hot, and will burn you if you get too close.

If the engine is running properly and a restriction in the exhaust is not present, the engine will accelerate quickly without having to labor. There should be a drastic difference in the amount of exhaust coming from the tailpipe when you allow the engine to idle as compared to when you "goose" the gas pedal. There should also be no visible signs of soot or black smoke coming from the tailpipe, or at least not a significant amount. If there is a restriction, you won't notice the drastic difference in exhaust volume, and you may also detect soot, black smoke, and even actual debris or pieces of the catalytic converter coming out of the tail pipe. You will also notice that the engine has to really labor or struggle to accommodate the request for increased performance.

What should you do if a restriction is found? Take the vehicle to your mechanic and have him determine if the engine is running too rich. If the engine is found to be too rich, the problem must be corrected first before you spend the money on a replacement converter. If you don't fix the root problem, the engine will just stop up the new converter. Once the engine is running properly again and the restriction has been removed, then the problem should be corrected.

Most muffler shops offer aftermarket replacement converters at a fraction of the price of a new one from the dealership. Talk to your mechanic to see what he recommends for your make and model of car."
 

jimmy

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Alp,

Have you got it sorted yet?

If not I, I may be able to help now. I now have an account with a CAT supplier and they do univeral 'bullet CATS' to chop and weld into your existing pipework.

If you want a price I will need some dimensions, length, diameter of inlet and outlet etc.
 
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Alps

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Hi Jimmy,

sorry, must have missed your reply! I havent got it sorted yet, just been driving the car as little as possible!

I will try and get that info for you within the next few weeks as the cars going in for the scratch resprayed (after a year!) on monday! so i may loose the use of it fora week or so.

as far as i know it will be some kind of high flow cat that i will need.

thanks again, will speak to you soon

Alps
 
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Alps

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Jimmy thanks for that, i have had further developments on this

i managed to get the CATS ordered through CKlass on the US forum, surprisingly i paid £150 less shiopped than what i could`ve got them for here in the uk.

next problem was the fitting, the C36 uses some funky pipe work which would have been a mission to fit the cats straight onto, this led to plan B

been to Hayward and Scott in Basildon, they make custom stainless sports exhaust systems. They showed me their high performance CATS which are mental (£400 each), which are even better than the ones i bought from CKlass. they are now going to make a stainless front end up to the manifold and fit the cats i bought from CKlass, the only AMG bit wil be the back box! 3" bore all the way to the front.

www.haywardandscott.co.uk

it would be interesting to hear if anyone has heard of them or had a system done by them before?
 

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afaik there is no MOT requirement for a catalytic converter. the key word here is that CAT test and catalytic onverter are different.

the MOT covers emissions - and thats it. a good tuned engine will have low emissions. the catalyst assists this.

there is so much bullsh!t running about about MOT tests.

http://www.motuk.co.uk/manual_710.htm
http://www.motuk.co.uk/manual_730.htm

there is no specific requirement for the car to actually have a catalyst - just to be able to pass the emissions test.

correct me if i'm wrong...
 

sym

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Have heard good things about Hayward & Scott . . . I also hear that they are quite open to the idea of group buys and club discounts if they make something to a particular template and there is enough interest :)

Jimmy - you might want to ask them about yours too !

S.
 

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