How long does a cat live?

whats the life expectancy of a cat converter in relation to the rest of the exhaust system? My '96 300tdi has an exhaust system comprising of 50% repair bandage, a twice repaired rear box and a few tin cans with jubilee clips so I thought it was about due a new one.
I nearly fell over when I saw how much a full system including the cat was, but the rest of the system excluding the cat is only about £38.
The down pipe, flexi coupling and the cat itself don't appear to be in to bad condition, there is no visible corrosion and its not blowing anywhere.
I would have imagined that the cat would corrode at a similar rate to the rest of the system, but it looks loads newer and I cant imagine that someone would go to the expense of replacing the cat and leaving the rest of the old system on.
So, do cats have a longer life than the rest of the system? the disco is 17 years old now, so should I replace the cat as a matter of course or is its external condition indicative of it its functioning life? I'd rather spend £38 than £245 if I dont have to but if the cat is too old to be working properly can it do any harm?
Any advise will be appreciated.

Depends how fast it uses its 9 lives

About 10 years or so depending on cars, dogs... oh, someone beat me to it.

Joking aside if it looks ok, keep it. If it doesn't, bin it and replace it with a piece of straight pipe without a cat. You don't need it.

sidewaysste said:

About 10 years or so depending on cars, dogs... oh, someone beat me to it.

Joking aside if it looks ok, keep it. If it doesn't, bin it and replace it with a piece of straight pipe without a cat. You don't need it.

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I have just discovered that self same thing while trawling the net to find the implications of not having one at all. Apparently, the cat's life span is shortened dramatically by mis-use which seems to include both physical and thermal shock ( i.e being hit by rocks or plunged into cold water) so do all you serious wading off roaders run your diesels cat-free? I also just read that removing it can improve mpg and improves power. So the two questions this begs are..
1/ how accurate is that info
and
2/ could the entire system be replace with an off the shelf non cat exhaust for a 300tdi from somewhere like Paddock's?

This will save you a few quid

Exhaust Complete System 300Tdi 94-98 ESR2391 ESR2297 Island 4x4 - Specialists in Land Rover and Range Rover Parts and accessories for all models. UK and worldwide mail order.

Fitted this kit to mine over 3 years (30,000 miles) and its still going strong. You don't need a cat on a diesel and its passes the mot no problem.

So basically, Yes.

Get rid of the cat and replace with a normal down pipe, the one on mine also fits a 'fender. Cost about £15 at the time. Whilst you are at it get rid of the EGR as well. Have has no trouble with MOT's for the last five years. You will find that the 300 will suddenly overtake things going up hill. Fuel stays about the same, but you can have far more fun for your buck. Then you could tweak the pump ............................and on and on.....................

cat steals heat from the exhaust.. hot cat doesnt corrode

Thanks for the link horse62, It looks like the best option if I decide to do away with the cat. I would ask, however, is there a lambda sensor on the 300, is there a threaded mount for it on that non cat exhaust, if not will it matter etc? Mate of mine took the cat off of a diesel Volvo and it ran like pig till he put it back on. Admittedly the volvo has a more complex ecu system but would I need to alter anything else on the 300?
How do I get rid of the EGR? I had a toyota surf some years back, it was a simple case of fitting a blanking plate between the mounting flanges on that. Is it a similar trick with the 300, or is it something a little more complex?
Also, I'm still curious about how the cat survives with some of you more serious off-roaders. Do you all remove it, or are they not as fragile as I'm led to believe and will survive being alternately rattled against rocks and plunged into cold water?

There are no sensors involved on the exhaust, its a straight swap. It took me a while to figure out that you have to jack the chassis up at the front to make space to twist the new down pipe into place. I used a bottle jack and a bit of 4"x4" fence post.

Heres a simple EGR blanking plate

EGR Blanking Kit 300TDI Island 4x4 - Specialists in Land Rover and Range Rover Parts and accessories for all models. UK and worldwide mail order.

EGR is simply removed by changing the top inlet hose for a straight one and removing two allen key bolts from the EGR removing the EGR completely, clean out the black marmite left behind and fit the blanking gasket and plate. 15 minute job.

http://www.landyzone.co.uk/lz/f38/how-300tdi-egr-blank-53441.html

As for the De cat what I did was remove the downpipe, three bolts, sawed the old rubber exhaust mounts off they were shot (make sure you buy 3 new ones) and then I had to cut my old exhaust in half as I couldn't undo the mid part.

Then a simple job of bolting the down pipe back on, wiggle the exhaust in with the new rubbers attached and a bit of washing up liquid on the rubbers to lube em up they slot back on. Total job time less than an hr if you don't have any bolt problems. I had a bolt that would not come undone on the down pipe, got there in the end.

I got this kit here that had the intercooler hose included.

LAND ROVER DISCOVERY 1 300 TDi EGR VALVE BLANKING KIT + INTERCOOLER HOSE | eBay

Thanks for that. I think for how cheap the entire replacement system is, I can swap it all off for the non-cat set up. I can hang on to the cat that comes off as, externally at least, it seems to be in ok condition and if the 300 suffers at all for the cat being removed it would only cost £38 to refit it with a new centre and rear section.

brettguise said:

I got this kit here that had the intercooler hose included.

LAND ROVER DISCOVERY 1 300 TDi EGR VALVE BLANKING KIT + INTERCOOLER HOSE | eBay

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Oh, and on the subject of intercoolers, I guess the intercooler is at the front next to the rad ( haven't looked that closely yet) but I have an intercooler with cooling fan that I bought to fit onto my surf but never fitted. Been toying with the idea of installing it on the disco with a bonnet scoop. Any one done this?

I threw my cat in the skip others took theirs to a scrap yard and got more than the complete exhaust system costs for it.

horse62 said:

I threw my cat in the skip others took theirs to a scrap yard and got more than the complete exhaust system costs for it.

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And you would of wished you kept it for next years mot:tea:

Thor1950 said:

And you would of wished you kept it for next years mot:tea:

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Are you then referring to DPFs which diesel cars have fitted and the MOT test on them.
https://www.gov.uk/government/news/new-rules-for-mot-to-test-for-diesel-particulate-filter

discool said:

Are you then referring to DPFs which diesel cars have fitted and the MOT test on them.
https://www.gov.uk/government/news/new-rules-for-mot-to-test-for-diesel-particulate-filter

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Interesting comment and link. Is the DPF part of the catalytic converter, or a seperate issue?

According to the AA website and various other sources, DPF's have only been mandatory on vehicles since 2009 and as far as I can tell don't seem to be an integral part of the exhaust system, so removing the cat from my teenage 300tdi wont make any difference to the MOT. I'm sure someone out there will correct me if I'm wrong though.

DPFs are fitted to modern diesels and are a serviceable item according to info in my wife's Merc C class handbook, there's even a light that comes on in the dash to say this it's required.

The DPF has to be 'recharged' or something similar, just a blast down the down the road 145mph should do it, not that I'm that interested but I had to read the handbook and then explain how the dash stuff works, as u do