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LIST OF ACTIONS REGARDING E51/E52 CATALYTIC CONVERTER ISSUES

Great. Hope it lasts. Do you still have rear cats fitted?
 
Sorry bit late I know but new member here.
Would a terra clean of cats not help every 20,000 miles or so, as long as your starting at manifold to end of exhaust.... Just an idea to keep all sweet and clear of crud?
No because if the cats are breaking up putting in cleaners will probably break up faster then more ceramic will get into the engine
 
There is ceramic in cylinders of every petrol engine - Ceramic insulates the centre spark plug electrode from the outer electrode. But not to worry about ceramics on spark plugs because they hardly ever break up or fail despite being inside the combustion chamber... Spark plug ceramics don't tend to fail unless the engine has been detonating or running too lean a mixture. Lean mixture can increase detonation and increases the potential for oxidation (because if we burn something with a lean mixture there is oxygen left over from the burn, where-as if we burn something with correct or rich mixture there is no oxygen left over after the burn).

We know that the ceramic matrix in Elgrand cats can and does break up.. but it isn't so much the 'heat of the burn' or 'heat of exhaust gas leaving the engine' that causes the cat matrix to break up. Spark plug ceramics look in better condition having run on some fuels that we expect to burn a bit hotter than they do running on other fuels that we expect to run a bit cooler.

There can definitely be a correlation between cat heat and cat failures. If we buy a new Elgrand cat and never fit it to a vehicle, never heat it up, it could sit on a shelf for hundreds of years and the ceramics inside wouldn't break up. If we found the remains of a catalytic converter in an Egyptian pyramid it's likely all the metal would have rusted away but the remaining ceramics would be in perfect condition.

The temperature of a cat isn't only effected by the temperature of the exhaust gas feeding it. Also the more of that gas (like when the engine is burning more fuel) the hotter it will get. And even more so, the more chemical reactions it has to do during cleaning up emissions the hotter it will get. If cats didn't produce heat themselves the hottest they could get would be to equal the temp of exhaust gas but cats get much hotter than heat of exhaust gas. If heat of exhaust gas were extremely hot but there wasn't much of it the cat might not get as hot as it would with a bit cooler exhaust gas but a lot more of it - I can hold my hand a distance over a small flame on a gas cooker but if I increase the size of the flame I would have to move my hand higher over the flame to not burn my hand, yet the small flame and the big flame are at the same temperature. If I ran the cooker on acetylene and oxygen instead of on natural gas and air I could expect to have to lift my hand further because the smaller acetylene flame could have overall more heat than the bigger natural gas flame. If instead of my hand I fitted a catalytic convertor over the cooker, the cat would also see the same incoming heat as my hand but the cat could get hotter than my hand because besides the heat coming from the cooker flame it would make it's own heat doing chemical reactions. When I ran the cooker on natural gas the hottest flame was a nice blue flame, if the cooker were a bit dodgy and gave a yellow flame it would be cooler. I could have my hand lower over a yellow flame than a blue flame but it isn't the same for a cat... A cat might get hotter over the yellow flame, because with the yellow flame it would make more heat inside the cat.

Nissan did a 'fuelling recall' which was supposed to address the cat problem. Looking at difference in readings from Elgrands that haven't had the recall compared to those that have had the recall the recall changed a few things but only slightly. Without the recall Elgrands continue to inject around 0.5ms of petrol on over-run and run a richer mixture than most engines on full load. After the recall Elgrands inject no fuel during over-run and fuelling enrichment at full engine load is leaned off a little (though is still rich). All cars go rich at full engine load so there's nothing unusual about going rich, or even a bit richer than we might expect. And in practice the fuelling recall seems to have done little to help the cat problem - I wouldn't expect it to either. To me the problem does seem to be a design issue on Elgrands.. design of the front cats, the position of them, and of course the 4 cat setup.

But what you really don't want if you have front cats still in place on Elgrands is overly rich mixture at high engine loads...
High engine loads means lots of exhaust gas flowing (bigger flame on the cooker, though this doesn't tell us the temperature of that flame).
Lean mixture means hotter exhaust gas, though that doesn't tell us the 'size of the flame' or the temperature that the cat will reach because with lean mixture the cat won't make as much heat inside itself, maybe not even with 'bigger flame'.
Rich mixture means cooler exhaust gas, though that doesn't tell us temperature that the cat will reach because again we don't know size of the flame, and with rich mixture the cat will do lots of exothermic chemical reactions which will vastly increase the temperature of the cat, exothermic chemical reactions can see the cat get hotter than it would with a lean mixture even though the temperature it was 'fed' at was cooler with the rich mixture than with the lean mixture.
The base temperature of exhaust gas doesn't directly correlate to the temperature that the cat will reach inside, that can depend more on the reactions the cat does or doesn't have to do inside (mixture, and type of fuel) and size of the flame (how much exhaust gas is flowing).
The worst situation is very rich overall at high engine loads (dirty emissions and 'big flame' so lots of dirty emissions to clean up) but with some cylinders running extremely rich mixture and some cylinders running a bit lean mixture, because then there's both way too much fuel plus oxygen feeding the cat and this will increase the temp inside the cat even more than a very rich mixture.

Wouldn't expect to find ceramic cats in a pyramid because they didn't have cats lol, but we do find Egyptian ceramics. Wouldn't expect to find metal matrix cats because they didn't have cats, and if they did they'd probably all have oxidated away by now ;-)
 
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I've got another couple of theories about the cat degradations that kinda makes sense to me.
Haven't seen these discussed anywhere before so I thought I'd throw them in the mix here.
I still suspect different process at play with this problem and one of them is expansion and contraction.
These forces cannot be resisted, they have to be engineered out.
However when it comes to the ceramic cats, they are really proper hard and absolutely brittle.
When you cycle from cold to hot & back to cold there is a natural limit to the number of times that material can do that before it cracks and collapses.
So yes, where the Elgrand lived before/after import plays a low temperature start (+/- 25 degrees) point and the usage/systems/fuel type/settings all have a high temperature (+/- 25 degrees) variable.
But effectively its that cold/hot/cold cycle variable that is the life limiting factor.
That's one theory.
Next theory is vibration.
The front cats are pretty much next door to the areas of the engine that will be creating the most amount of vibration.
Usual mounting point for the cat is further back and on rubber mounts.
Again those very hard and very brittle honeycomb ceramics just ain't gonna like that one little bit.
All okie kokie when newish but give the 'system' 10 years to loosen up and voila.
Broken cats.
 
I'm totally new to thinking about the science and mechanics here, but I do know a bit about ceramics and porcelain manufacture.
I'm also going to guess that (much like in my industry) there are very high quality ceramics, and very poor quality ceramics.
It seems that the ceramic matrix in cats is composed of cordierite and other ingredients. Those other ingredients can be absolutely critical to ceramic performance.
For instance, there was a case fifteen or so years ago where everyone wanted black polished porcelain floors. Normally very expensive to make but b&q found a Chinese supplier who was making them using industrial waste mineral salts, rather than high grade porcelain ingredients. Cutting a long story short, there were loads of problems and they caught a big cold.
(Chinese quality is generally brilliant now by the way).
Perhaps the quality is just rubbish in Elgrand cats?
Interesting read in Wikipedia on the subject: says that unburnt fuel is a killer, as is low grade fuel with a high ethanol content.
Sounds like it's a good idea to use super super!
 
Interesting read in Wikipedia on the subject: says that unburnt fuel is a killer, as is low grade fuel with a high ethanol content.
Sounds like it's a good idea to use super super!

Unburned fuel, i.e. too rich mixture, is a common killer of cats, and at high engine loads (analogy with the big flame again) will see off most cats in quick time.... But Elgrand cats fail anyway.
 
There is one other factor which I think helps break them people starting their engines from cold and thrashing them causes the catalytic converters to heat up too quickly especially in winter I never thrash my engine until I've done a minimum of 6 miles to make sure the whole engine is at normal running temperature especially in winter.
 
Leaving engine running on tick over for extended periods is no good for cats either.

PS. On cars with digital temperature gauges its surprising in winter that they look warmed up according to the traditional dash gauge but actually aren't and auto box takes much longer to warm up than expected too.
 
Sooooooo.... if I continue to drive as I currently do - like a very timid, gentle old man, and only press the happy pedal very delicately, my car will potentially last longer than if I...... how can I describe it.........?

HAVE FUN?!
 
Quick question without wanting to derail the thread... Where do I begin looking if I wanted to replace the front cats with something better?

I'd love an LPG conversion, really I would, but I don't have much confidence in the availability continuing.
Of course, if it's not a great deal more to have LPG instead of replacing front cats....
 
Gentle Bump?!
 
You'll have to have a manifold back system made with new cats included or have the front cats decored and fit a pair of good rear cats.
 
What is the most common failure on the engine after cat failure?

Crankshaft bearings running out? Or something else?

In a legal procedure with a local shop hence they decored one side and didn't want to do the other as they assured me it would be fine for the remainder of my trip.
Well that didn't work out so good, now my engine is complete scrap
 
Having 're read this entire thread ( https://forum.elgrandoc.uk/threads/...and-the-do-not-remove-rear-cats-debate.18398/ ) again this morning here are my conclusions and the options available of which there are at least half a dozen. Rough costs are an estimate on people's postings throughout the forum. So please dont abuse me if some are slightly inaccurate!!! No agenda as I don't even own an e51 so completely impartial take on the matter.

Option 1.
Remove/decore the rear cats. Cost £100
Pros- cheap and easy. Van down time = a couple of hours.
Cons- not a 100% safe fix, and could still have future problems from front cats blocking themselves.

Option 2.
Remove/decore the front cats leaving the rears. Cost £400
Pros- eliminates chance of cat break down and blockage. Still a reasonable price.
Cons- more difficult to do, greater difficulty finding someone to carry out the work. Emissions feed back unknown. Van down time = 1 day

Option 3.
Remove/decore both front and rear cats and replace with aftermarket cats down stream. Cost £900
Pros- completely eliminates risk of old cats disintegrating. Healthy emmisions.
Cons- more expensive, very, very slim chance aftermarket cat could disintegrate in future. Van down time = 1 day.

Option 4.
Complete new stainless exhaust system with aftermarket cats. Cost £ 1200-1700
Pros- removes risk of original cat disintegration, sound lovely will last a long time.
Cons- more expensive. Very, very slim chance of cat failure. Van down time = 1 day

Option 5.
Lpg install. With full cat removal. Cost £2000+
Pros- eliminates any possibility of cat failure, cheaper fuel for future use. No emission worries at MOT as tested on lpg not petrol.
Cons- more expensive process, future lpg servicing costs, not all systems/setups are perfect causing possibility of other mechanical issues. Van down time = 3/4 days. Plus delivery/accommodation costs during process.

Option 6.
Carry on as you are with whatever process you've already done or not done.
Pros- live in a world of bliss and worry about what if's later. And enjoy life and your Elgrand.
Cons- your car could (But might not) breakdown at any moment. Expensive repair bill (£2.5k) or scrap value only.

Do with this what you will. The info is out there for anyone to read and make an informed decision on how, why, or what you want to do to extend the life of an Elgrand.
Don't think this discussion will ever go away, so long as people are still buying elgrands and not doing their homework on them.
Hello all, am new to the forum, so apologies for blundering in.
can I ask if this is mileage relevant? I have a 2007 E51 recently acquired with about 63K miles , when is a good time to consider the options?
Thanks
Ashferdinand
 
Hello all, am new to the forum, so apologies for blundering in.
can I ask if this is mileage relevant? I have a 2007 E51 recently acquired with about 63K miles , when is a good time to consider the options?
Thanks
Ashferdinand
A good time to consider the options is now!!
This is what RAC say about lifespan of cats

Catalytic converters often last for at least 10 years, or between 70,000 and 100,000 miles.

However, it’s possible that the catalytic converter on a car that is used only for short start-stop journeys could wear out faster because the engine and cat won’t be able to reach their optimum operating temperature before being switched off.


So your car is already over 10 years old and nearly 70k miles. And you don't know its history in Japan.

In my view- Don't delay!!
 
Having 're read this entire thread ( https://forum.elgrandoc.uk/threads/...and-the-do-not-remove-rear-cats-debate.18398/ ) again this morning here are my conclusions and the options available of which there are at least half a dozen. Rough costs are an estimate on people's postings throughout the forum. So please dont abuse me if some are slightly inaccurate!!! No agenda as I don't even own an e51 so completely impartial take on the matter.

Option 1.
Remove/decore the rear cats. Cost £100
Pros- cheap and easy. Van down time = a couple of hours.
Cons- not a 100% safe fix, and could still have future problems from front cats blocking themselves.

Option 2.
Remove/decore the front cats leaving the rears. Cost £400
Pros- eliminates chance of cat break down and blockage. Still a reasonable price.
Cons- more difficult to do, greater difficulty finding someone to carry out the work. Emissions feed back unknown. Van down time = 1 day

Option 3.
Remove/decore both front and rear cats and replace with aftermarket cats down stream. Cost £900
Pros- completely eliminates risk of old cats disintegrating. Healthy emmisions.
Cons- more expensive, very, very slim chance aftermarket cat could disintegrate in future. Van down time = 1 day.

Option 4.
Complete new stainless exhaust system with aftermarket cats. Cost £ 1200-1700
Pros- removes risk of original cat disintegration, sound lovely will last a long time.
Cons- more expensive. Very, very slim chance of cat failure. Van down time = 1 day

Option 5.
Lpg install. With full cat removal. Cost £2000+
Pros- eliminates any possibility of cat failure, cheaper fuel for future use. No emission worries at MOT as tested on lpg not petrol.
Cons- more expensive process, future lpg servicing costs, not all systems/setups are perfect causing possibility of other mechanical issues. Van down time = 3/4 days. Plus delivery/accommodation costs during process.

Option 6.
Carry on as you are with whatever process you've already done or not done.
Pros- live in a world of bliss and worry about what if's later. And enjoy life and your Elgrand.
Cons- your car could (But might not) breakdown at any moment. Expensive repair bill (£2.5k) or scrap value only.

Do with this what you will. The info is out there for anyone to read and make an informed decision on how, why, or what you want to do to extend the life of an Elgrand.
Don't think this discussion will ever go away, so long as people are still buying elgrands and not doing their homework on them.
Thanks for this… I was told I was buying an E51, but as it was an import, there was no Australian paperwork saying what model it actually was. So I’ve done a check on the chassis number which revealed it is actually an E50 Nov 2001… for which I am actually a bit relieved. Now I’ll have to keep an eye out for any issues with the E50. 😳 What a great forum.
 
Having 're read this entire thread ( https://forum.elgrandoc.uk/threads/...and-the-do-not-remove-rear-cats-debate.18398/ ) again this morning here are my conclusions and the options available of which there are at least half a dozen. Rough costs are an estimate on people's postings throughout the forum. So please dont abuse me if some are slightly inaccurate!!! No agenda as I don't even own an e51 so completely impartial take on the matter.

Option 1.
Remove/decore the rear cats. Cost £100
Pros- cheap and easy. Van down time = a couple of hours.
Cons- not a 100% safe fix, and could still have future problems from front cats blocking themselves.

Option 2.
Remove/decore the front cats leaving the rears. Cost £400
Pros- eliminates chance of cat break down and blockage. Still a reasonable price.
Cons- more difficult to do, greater difficulty finding someone to carry out the work. Emissions feed back unknown. Van down time = 1 day

Option 3.
Remove/decore both front and rear cats and replace with aftermarket cats down stream. Cost £900
Pros- completely eliminates risk of old cats disintegrating. Healthy emmisions.
Cons- more expensive, very, very slim chance aftermarket cat could disintegrate in future. Van down time = 1 day.

Option 4.
Complete new stainless exhaust system with aftermarket cats. Cost £ 1200-1700
Pros- removes risk of original cat disintegration, sound lovely will last a long time.
Cons- more expensive. Very, very slim chance of cat failure. Van down time = 1 day

Option 5.
Lpg install. With full cat removal. Cost £2000+
Pros- eliminates any possibility of cat failure, cheaper fuel for future use. No emission worries at MOT as tested on lpg not petrol.
Cons- more expensive process, future lpg servicing costs, not all systems/setups are perfect causing possibility of other mechanical issues. Van down time = 3/4 days. Plus delivery/accommodation costs during process.

Option 6.
Carry on as you are with whatever process you've already done or not done.
Pros- live in a world of bliss and worry about what if's later. And enjoy life and your Elgrand.
Cons- your car could (But might not) breakdown at any moment. Expensive repair bill (£2.5k) or scrap value only.

Do with this what you will. The info is out there for anyone to read and make an informed decision on how, why, or what you want to do to extend the life of an Elgrand.
Don't think this discussion will ever go away, so long as people are still buying elgrands and not doing their homework on them.
Is this just for E51's. I am looking to get an E50. Anything I need to know about the e50?
 
Evening all! My brother in law has quite kindly offered to weld the cats back up for me, once I have decored them, as I haven’t done any welding for about 30 years. I have a couple of questions though. What thickness steel plate do I need to get to weld over the holes and how big a hole do people normally make to knock out the insides? TIA.
 
Are those prices roughly correct? I've had it in my head it would be around £1500 or so for front decored given what's involved not £400. Maybe those are northern prices. If that's really the case I can stop stressing lol. Years away from a purchase but like to research.
 
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