Catalytic converters - Starstruck
Has anyone had experiance of having to replace a catalytic converter?
My sons Mercedes 190E 2.0 needs a replacment soon and he has been
told the cost will be over £1000 !!!!!!!!!!!!
Car is nine years old
Re: Catalytic converters - Guy Lacey
Sounds about right. These things have a definite lifespan and 10 years doesn't sound too out of this world, even if the price does.

It all depends how they've been treated. Also, bear in mind that a 10 year old cat will be one of the first fitted as standard so will also be quite primitive - nothing like the types fitted today.
Catalytic converters - David Lacey
An aftermarket catalyst at will be much much cheaper.
We have used many of their fuel injection components and catalysts and have had NO problems at all.


PS Not sure if they retail outside the trade, but well worth a shot.
Re: Catalytic converters - Alwyn
I am sure others know far more about this than me but is it neccessary for a 10 year old car to have a cat?

I have been told by MOT chappies that if the cat on my 1990 Volvo 740 fails then I can have a straight through pipe fitted as cats were not mandatory until perhaps 1992/3.

There might be a problem with the oxygen sensor but perhaps this could be cured by taking out the warning light: or does it need some other adjustment?

Would that work with the Mercedes?

I was also told by an exhaust fitter that he imported a cat for an American car and the cost of the cat was £19. Yes, nineteen pounds!

True or false?

Volvo quoted £700 for mine (if it goes): the exhaust fitter said £300.

Re: Catalytic converters - Adam Going (Tune-Up Ltd)
If removing a Cat you MUST retain the Lambda (Oxygen) Sensor, creating a new fitting for it in the downpipe if necessary, as the ECU will not control mixture without this input. The warning light is a general system warning, not just about the Lambda Sensor.

My understanding is that anything pre Aug '92 can have the Cat removed.

Regards, Adam
Re: Catalytic converters - Andrew Tarr
Correct, Adam - converters became obligatory for petrols from th K plate (Aug.92). Some cars had them before that, and they can be de-catted.
Catalytic converters - David Lacey

In a word, NO! You can't use a resistor.

Fitting an oxy sensor into a decatted exhaust system is not difficult - even my 1st year Modern Apprentice has done one!

The bosses required to fit them are readily available - if not any competant machine shop should be able to make you one.

To enable the fuel injection system to operate efficiently, the ECU needs to see a voltage swing from the oxy sensor - with a resistor you would not be able to achieve this.
Perhaps some whizz-kid could indeed manufacture a 'box' to simulate the signal. Come to think of it, they may already be available for use with LPG conversions on EOBD Compliant cars.

Re: Catalytic converters - Honest John
Adam is right here. As usual.

Re: Catalytic converters - Andrew Hamilton
These expensive CATs are going to force the early scrapping of 1993 onward cars. Perhaps people will start buying up pre-1992 cars just to get appropriate registrations and dump the ecu!
Re: Catalytic converters - Adam Going (Tune-Up Ltd)
The way a car is tested for MOT purposes (ie whether or not it needs a Cat) is determined by it's "date of first registration", not the registration plate it currently carries. Whilst it may be technically possible to "dump the ECU" by throwing away all the injection system and fitting carbs to some engines (assuming manifolds are avaliable) you would probably have to change the ignition as well, and on some engine there is simply no provisions for a distributor any more. Then there is the question of the links between the engine managemnet systems and the immobilisers, audio, heating/ventilation, airbag, braking, and other ECUs.................

Happy days !

Catalytic converters - David Lacey
The giveaway for a broken substrate is a rattling from the catalyst itself or subsequent exhaust sections. Never seen one block and exhaust system (yet) although it is possible I guess. We have replaced perfectly serviceable exhaust centre and rear sections due to pieces of broken catalyst inside which have proved to be un-retrievable by the usual methods. (Holding it upside down!)

Re: Catalytic converters - Tomo
Could you substitute a resistor of equal value to that of the sensor, for normal operation?
Re: Catalytic converters - Cliff Pope
In what way exactly does a cat 'fail'?
Do they physically rust or fracture, just like any silencer, or do they simply fail internally and cease catalysing?
If the latter, and the car is not legally obliged to have one, can't it just be left alone, or its insides bashed out?
Removal of catalytic converters - David Lacey
No adjustments/compensation is needed when decatting, in my experience.
I decatted my 1995 Golf VR6 and it blew the others away on the rollers!
(BTW before I get told off for decatting a car that needed a cat, the engine etc was fitted into a 1988 MK2 Golf)

Catalysts fail because of (i)Substrate meltdown due to fuel entering the cat (Misfires) (ii) Impact damage (Speedhumps) (iii) Thermal damage - driving through floodwater with a hot catalyst (iv) Substrate contamination - incorrect fuels, oil burning etc etc..
Catalysts do not corrode - the shells are made from Stainless Steel.

If the car doesn't require a cat and it is knackered, then there is nothing stopping you 'bashing' {as you so eloquently put it, Cliff!} the internals out. The only downside to this is some resultant booming within the exhaust due to a large chamber within the system!

If you do decide to 'bash' any internals out, please avoid breathing any of the dust etc that comes out. Who knows what it contains.


Re: Removal of catalytic converters - Charles

If a cat element breaks up it usually blocks the next silencer resulting in next to no performance from the engine.

Re: Catalytic converters - Rob
Does there need to be any alteration to the ECU when decatting? (Something to do with the change in exhaust back pressure, perhaps).

Re: Catalytic converters - geoff
Try based in birmingham.
Or go to for more info on Mercs or cheaper independent servicing.
NO conection by me but Andy does talk sense on site and does not plug himself excesively.

Value my car