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E51 The E51 Catalytic Converter Problem

Aranadin said:
Hi everyone, I've just been chatting to my father about getting his cats either de-cored or replaced, the question is, does anybody know of someone who can do this for him in the Middlesbrough area? Thanks.
Click to expand...
Have a chat with dave at vine place, Elgrand dealer just up the A19 in wingate. 😎👍
 
Hey guys, just want to confirm something. I was talking to a dealer today and he says that this cat converter problem was fixed by the time they released the s2 e51, however, from what I read here the problem comes from the fact that e51's have a quad cat exhaust set up.

Just want to confirm that no matter what series of the e51 I get I'll most likely have to mod the cat converters assuming it hasn't already been done in Japan right?
 
I got my Elgrand 2 weeks ago and I had the rear cat removal done included in the cost (I blagged that haha) but it was only £180 to have done anyway that was with jay car finder in Bradford, the cut the inside of the cats out from the top and welded it back together so from underneath it still looks like the cat or is the cat but its just hollowed out and you cant see where anything has been tampered with so the mot tester would just think it is standard!
 
Lpgc said:
We're into the can of worms again...

Why say move front cats back slightly? I'd bet the answer is because some on forum reckon the front cats are too close to the engine exhaust ports... (which imo may be a contributing factor). But with that said it then begs the questions - How far back should these new front cats be fitted (so they won't suffer the same fate as original cats)? If the problem was just the location of original cats (too close to exhaust ports) then instead of fitting new cats why not just fit a spacer between manifold and original cats (if front cats seem in good condition)? Does the suggestion to replace front cats with aftermarket cats and also to fit aftermarket cats further back in the exhaust (further away from exhaust ports) reflect a belief that the problem is due to both the original cats being prone to failure (even if they were fitted further back) and being fitted too close or just one of these?

If an Elgrand will pass MOT running on petrol with front cats decored and rear cats still fitted, why buy new front cats when original front cats could be gutted (no parts to buy just labour for decoring front cats)?

For those running on LPG, if an Elgrand will pass MOT with all cats decored, decoring all of them (no parts to buy) may give more peace of mind than any other option. No cats at all fitted means absolutely no chance of any cat failure in any circumstances.. In contrast, an engine problem such as a stuck open petrol injector or badly broken PCV valve (or burning oil for any other reason e.g. valve stem seals etc) could cause any cat to fail, a new aftermarket cat may suffer the same fate as original spec cats under such conditions and maybe even in the same amount of time.

I still think decoring rear cats will save the majority of engines in the case front cats break up. I agree this isn't a total fix and know there's still a risk of front cats blocking themselves up (and I believe I was among the first to say so). But I don't think there's enough evidence yet to know how well aftermarket cats will fare in future, perhaps especially not if they're fitted as close to the engine as original cats were. For the amount of time people have been replacing front cats with aftermarket cats (this started relatively recently?) we probably wouldn't expect new original spec cats to have failed since being fitted either. The best 'sports cats' are the least restrictive to flow of exhaust gasses but no cat flows as well as a pipe with no internal restrictions or as well as a cat that has been gutted.

My personal level of confidence in an Elgrand not suffering cat problems over the long term goes something like this:

Totally original spec exhaust, all cats in place 30% confidence.
Decat rear cats 80% confidence
Decat front cats leaving rear cats in place 97% confidence
Fit aftermarket front cats leaving rear cats in place 87% confidence
Fit aftermarket front cats and gut rear cats 93% confidence
Decat all cats 100% confidence.

Those figures assume no engine problems, they could change very quickly if there are any engine problems involving excess oil or fuel getting into the exhaust system. The only figure that would not change in any circumstances is the decat all cats option.
Click to expand...
Morning, would decating the front cats leaving the rears in place cause an issue for the sensors?
 
Hallam said:
I got my Elgrand 2 weeks ago and I had the rear cat removal done included in the cost (I blagged that haha) but it was only £180 to have done anyway that was with jay car finder in Bradford, the cut the inside of the cats out from the top and welded it back together so from underneath it still looks like the cat or is the cat but its just hollowed out and you cant see where anything has been tampered with so the mot tester would just think it is standard!
Click to expand...
If someone asks me to decore rear cats at same time as LPG conversion I charge £100. The short passenger side rear cat doesn't need to be cut into anyway, it's short and straight enough that it's internals can be accessed and removed from the ends. The drivers side rear cat does need to be cut into to decore, it is in the middle of a long bendy section. It would be crazy to make the cut/weld where it would be visible when it is almost just as easy to make the cut/weld on the top which is hidden by it's heat-shield.

Turkish said:
Morning, would decating the front cats leaving the rears in place cause an issue for the sensors?
Click to expand...
No aspect of de-catting causes an issue for sensors or the engine management system (no Mil light errors) provided the oxygen/lambda sensors are left in place. The question is whether or not a decatted Elgrand would pass an emissions test running on petrol. If all 4 cats are gutted it very likely will not pass an emissions test if it is running on petrol, although it will pass with all 4 cats gutted if it is running on LPG.

It seems that an Elgrand will pass an emissions test running on petrol if 1. Only the front cats are left in place (and are intact), rear cats are gutted. Or 2 will pass an emissions test running on petrol if rear cats are left in place (and are intact), front cats gutted. Any vehicle (including Elgrands) with properly working fuel system and engine in OK condition will pass an emissions test if it is converted to LPG regardless of 1, 2, or even 1+2 together.

1. Is probably better for emissions provided front cats are intact and is relatively quick and easy compared to 2.
2. Is better at preventing problems than 1 but is a lot more work.
1 + 2 together completely removes any possibility of any cat failure, no cats, no risk of cat failure.

Some on forum including (iirc) @stevemen (who runs an Elgrand scrapyard) reckon the front cat problem may be due to how close front cats are to the exhaust manifold and exhaust ports, I don't know if sports cats would be spaced any further from the exhaust manifold and exhaust ports.
 
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Many thanks for the prompt response, my buddy makes and fabricates exhausts, specialist stuff and one off’s. I am looking to get him to do the work, I was thinking of replacing the front Cats with sports Cats and straight through pipe where the rears are now.
after hearing some horror stories regarding Cat issues and only buying the Elgrand last week...worry has started to set in lol
 
What's the longest (time and mileage) anyone has had replacement / sports front cats fitted on the front of an Elgrand?

And is that long enough / far enough to give the impression that aftermarket / sports cats won't suffer the same fate as standard cats and cause the same problems as failed standard cats given enough time / distance?

Nissan make a wide range of vehicles, most of which seem no more likely to suffer failed cats (or failed cats to cause the engine to fail if they do fail) than other make/model vehicles. If the front cats are of a similar design / spec to those on other vehicles is it the design of the cats that is the problem or is it the overall design including proximity of cats to the manifold that is the problem? And would replacement cats be any further from the manifold?

The proximity question isn't one that I raised and I don't know the answer. Before the question about proximity was raised I would have assumed problems were due to design of the cats, then at first I doubted proximity, but having considered all the above I'm now 50/50 on proximity.

Now let's consider a situation.. Someone owns an E51 made in 2007 that's done 130000km. Their Elgrand suffers a cat problem but let's look on the bright side and assume they realise a cat is blocked so stop driving and immediately turn the engine off thus saving the engine from damage. Now they have to consider the options. Their Elgrand is in great condition and they really like it, they can't imagine selling it in the next 10 years - should they decore front cats, or have new standard Nissan front cats fitted, or have aftermarket / sports type cats fitted? Aftermarket / sports cats may be cheaper than Nissan original spec cats but what if they fail in less time / mileage than the original spec cats and how do we know they won't?
 
So many questions, so few answers. Whatever you do it will be better than doing nothing.
 
Stempyuno said:
So many questions, so few answers. Whatever you do it will be better than doing nothing.
Click to expand...
Yes, a decore will mean no chance of a failed front cat, any type of replacement cat will be a new cat.
 
Karl said:
THIS IS NOT FORUM LORE. THIS IS NOT A MYTH. THERE HAVE BEEN MANY DOCUMENTED INCIDENTS WHERE OWNERS HAVE HAD THEIR ENGINE BLOW UP BECAUSE OF THIS ISSUE. YOU HAVE BEEN WARNED.

CHECK OUT THIS THREAD FOR PROOF

LIST OF AFFECTED MEMBERS

The problem

A widely known issue with the Nissan Elgrand E51 is that the rear cats get blocked causing catastrophic
damage to the engine.

The problem starts with the fact that the E51 has a QUAD CAT SYSTEM. This means there is a PRIMARY and a SECONDARY catalytic converter on EACH BANK of the V6 engine.

The PRIMARY cats are the ROOT CAUSE of problem. Through use, after heating up and cooling down, they start to deteriorate. This happens with ANY ceramic catalytic converter when they reach the end of the their life. As the PRIMARY cats starts to break down and fall apart, the debris is pushed back through the exhaust. At this point, they come into contact with the SECONDARY cats, which creates a blockage.

As more and more of the PRIMARY falls apart, the blockage will prevent any exhaust gasses getting out. The exhaust gases (and dust particles) then build up pressure and go to the only place they can, back into the engine. It doesn't take a mechanic to know that if you put exhaust gas mixed with catalytic converter debris back into an engine, it's not going to last long.

So, that covers the problem, what can you do about it?

There are 3 main options.

1/ DECORE the SECONDARY CATS. This is a simple process. You remove the secondary cats, cut an opening in the top, smash the internals out, weld the opening shut again and re-fit them. This removes the point at which the debris from the PRIMARY cats will get stuck creating a blockage. The debris is just pushed out the back of the exhaust. THIS IS NOT A 100% SAFE OPTION. Debris can still trap itself within the primary cat or the mid box of the exhaust. Although removing the rear cars reduces the chances of catastrophic failure exponentially... it will not 100% stop it from happening.

2/ Remove the SECONDARY CATS. Same principle as option 1, but you remove the cats altogether and replace with a straight through pipe. This is more costly than option 1, BUT what it means is that when it comes to MOT time, you still have the cats to fit to the vehicle if there are ever any issues. As with option 1, this is not a 100% failsafe option for the same reason outlined above.

3/ By far the most expensive option, but still an availability if you have the funds to allow it. Replace the WHOLE system (Manifold back) with a custom made stainless exhaust with single stage, high flow metal sports cat. Dig deep for this one, but the noise will be worth it :) - This option will 100% remove the risk of damage caused by the standard catalytic converter failure problem.

REGARDLESS OF WHAT METHOD YOU CHOOSE - YOU MUST CHECK FOR DEBRIS FROM FAILING FRONT CATS AND INSPECT THEM BEFORE YOU MOVE FORWARD. IF THEY HAVE ALREADY STARTED TO DETERIORATE, YOU SHOULD HAVE THE WHOLE SYSTEM REPLACED AND THE ENGINE HEALTH CHECKED BY A PROFESSIONAL.​

But what about.......?

You will fail an MOT if you remove the rear cats and the tester knows they should be there. So if you do fit straight through pipes, keep the cats and then you can fit them again at a later date if you need to.
If you go for option 1, make sure the access hole is cut in the top of the cat so that the head shield will cover the weld when it's sealed up again. If the hole is on the bottom, and the tester can see that they have been tampered with, he'll fail it.

Emissions are NOT affected by removal of the secondary cats. They are only part of the system due to the strict "cold starting" emissions policies in Japan. In the UK the emissions test is done on a warm engine, and therefore the secondary cats serve ZERO purpose.

Is this legal?

I don't know what PC Plod can do about you removing/modifying the cats. But, if you tell an MOT tester that you have modified the cats in any way, and it fails, then technically the car is not road worthy. We know this is bollocks. It'll still pass the emissions test, it will still drive perfectly OK, and you have removed the risk of having your engine blow up when belting down the motorway at no more than 70 (of course).

The choice on what you do is up to you. Keep them if you want. But then every time you drive your E51 you will be wondering when the engine is going to blow up. I know from a personal point of view, I'd rather take the risk with the MOT tester than have catastrophic engine failure and a £4500 engine rebuild bill.

I heard about a Recall for this problem!?

The recall has NOTHING to do with this problem. All it will do is prolong the inevitable. The recall was put out to adjust the fuelling. If your car is subject to the recall, the engine map was putting too much fuel into the engine. This meant that excess fuel was getting blown out of the engine following combustion and then igniting in the exhaust system due to the heat. This meant that the exhaust was getting a lot hotter than it should causing premature deterioration of the primary cats.
With the recall in place, the engine will not overfuel... but it does not mean that the primary cats will not start to disintegrate over time.

There have been at least 2 instances that I know of where a car that was NOT on the recall list has had the engine fail because of blocked cats.

Why does this need doing?

Cars built for EU and UK roads are designed with the climate in mind. Therefore, as part of the manufacture process, there are treatments applied to the bare metal to prevent the chassis corroding. JDM cars are NOT done, because the climate in Japan is very different to ours.

The underseal is required to ensure that your car doesn't turn into a pile of rust over the winter. More importantly, because you are doing this AFTERMARKET, it is something that is seen as temporary, not permanent. The products applied will, over time, wear off or get damaged thus leaving untreated metal to come into contact with salt and moisture.

The better the product you use, the longer it's life. There may even be products out there that come with a "life of the car guarantee"... but I'm sure they'll cost more than £400!

With that in mind, discuss the options available with the garage you chose for your underseal and discuss repeat applications and how often they will be required. If they want your continued business, they will offer all options and tailor the service to your requirements and budget.
Click to expand...
Thanks for the info, I had cats de-cored.
 
Karl said:
THIS IS NOT FORUM LORE. THIS IS NOT A MYTH. THERE HAVE BEEN MANY DOCUMENTED INCIDENTS WHERE OWNERS HAVE HAD THEIR ENGINE BLOW UP BECAUSE OF THIS ISSUE. YOU HAVE BEEN WARNED.

CHECK OUT THIS THREAD FOR PROOF

LIST OF AFFECTED MEMBERS

The problem

A widely known issue with the Nissan Elgrand E51 is that the rear cats get blocked causing catastrophic
damage to the engine.

The problem starts with the fact that the E51 has a QUAD CAT SYSTEM. This means there is a PRIMARY and a SECONDARY catalytic converter on EACH BANK of the V6 engine.

The PRIMARY cats are the ROOT CAUSE of problem. Through use, after heating up and cooling down, they start to deteriorate. This happens with ANY ceramic catalytic converter when they reach the end of the their life. As the PRIMARY cats starts to break down and fall apart, the debris is pushed back through the exhaust. At this point, they come into contact with the SECONDARY cats, which creates a blockage.

As more and more of the PRIMARY falls apart, the blockage will prevent any exhaust gasses getting out. The exhaust gases (and dust particles) then build up pressure and go to the only place they can, back into the engine. It doesn't take a mechanic to know that if you put exhaust gas mixed with catalytic converter debris back into an engine, it's not going to last long.

So, that covers the problem, what can you do about it?

There are 3 main options.

1/ DECORE the SECONDARY CATS. This is a simple process. You remove the secondary cats, cut an opening in the top, smash the internals out, weld the opening shut again and re-fit them. This removes the point at which the debris from the PRIMARY cats will get stuck creating a blockage. The debris is just pushed out the back of the exhaust. THIS IS NOT A 100% SAFE OPTION. Debris can still trap itself within the primary cat or the mid box of the exhaust. Although removing the rear cars reduces the chances of catastrophic failure exponentially... it will not 100% stop it from happening.

2/ Remove the SECONDARY CATS. Same principle as option 1, but you remove the cats altogether and replace with a straight through pipe. This is more costly than option 1, BUT what it means is that when it comes to MOT time, you still have the cats to fit to the vehicle if there are ever any issues. As with option 1, this is not a 100% failsafe option for the same reason outlined above.

3/ By far the most expensive option, but still an availability if you have the funds to allow it. Replace the WHOLE system (Manifold back) with a custom made stainless exhaust with single stage, high flow metal sports cat. Dig deep for this one, but the noise will be worth it :) - This option will 100% remove the risk of damage caused by the standard catalytic converter failure problem.

REGARDLESS OF WHAT METHOD YOU CHOOSE - YOU MUST CHECK FOR DEBRIS FROM FAILING FRONT CATS AND INSPECT THEM BEFORE YOU MOVE FORWARD. IF THEY HAVE ALREADY STARTED TO DETERIORATE, YOU SHOULD HAVE THE WHOLE SYSTEM REPLACED AND THE ENGINE HEALTH CHECKED BY A PROFESSIONAL.​

But what about.......?

You will fail an MOT if you remove the rear cats and the tester knows they should be there. So if you do fit straight through pipes, keep the cats and then you can fit them again at a later date if you need to.
If you go for option 1, make sure the access hole is cut in the top of the cat so that the head shield will cover the weld when it's sealed up again. If the hole is on the bottom, and the tester can see that they have been tampered with, he'll fail it.

Emissions are NOT affected by removal of the secondary cats. They are only part of the system due to the strict "cold starting" emissions policies in Japan. In the UK the emissions test is done on a warm engine, and therefore the secondary cats serve ZERO purpose.

Is this legal?

I don't know what PC Plod can do about you removing/modifying the cats. But, if you tell an MOT tester that you have modified the cats in any way, and it fails, then technically the car is not road worthy. We know this is bollocks. It'll still pass the emissions test, it will still drive perfectly OK, and you have removed the risk of having your engine blow up when belting down the motorway at no more than 70 (of course).

The choice on what you do is up to you. Keep them if you want. But then every time you drive your E51 you will be wondering when the engine is going to blow up. I know from a personal point of view, I'd rather take the risk with the MOT tester than have catastrophic engine failure and a £4500 engine rebuild bill.

I heard about a Recall for this problem!?

The recall has NOTHING to do with this problem. All it will do is prolong the inevitable. The recall was put out to adjust the fuelling. If your car is subject to the recall, the engine map was putting too much fuel into the engine. This meant that excess fuel was getting blown out of the engine following combustion and then igniting in the exhaust system due to the heat. This meant that the exhaust was getting a lot hotter than it should causing premature deterioration of the primary cats.
With the recall in place, the engine will not overfuel... but it does not mean that the primary cats will not start to disintegrate over time.

There have been at least 2 instances that I know of where a car that was NOT on the recall list has had the engine fail because of blocked cats.

Why does this need doing?

Cars built for EU and UK roads are designed with the climate in mind. Therefore, as part of the manufacture process, there are treatments applied to the bare metal to prevent the chassis corroding. JDM cars are NOT done, because the climate in Japan is very different to ours.

The underseal is required to ensure that your car doesn't turn into a pile of rust over the winter. More importantly, because you are doing this AFTERMARKET, it is something that is seen as temporary, not permanent. The products applied will, over time, wear off or get damaged thus leaving untreated metal to come into contact with salt and moisture.

The better the product you use, the longer it's life. There may even be products out there that come with a "life of the car guarantee"... but I'm sure they'll cost more than £400!

With that in mind, discuss the options available with the garage you chose for your underseal and discuss repeat applications and how often they will be required. If they want your continued business, they will offer all options and tailor the service to your requirements and budget.
Click to expand...
Hi @Tana Here’s info why you should have rears Decored & the different methods .
Tony Banks exhausts here in Leeds has Elgrand experience , he should be of help - all depends which option you choose .🙂
 
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Guys, finally managed to get the CAT's done at Stuart Spencer's this week at long last :D

I did order some from @Winchester but he's been having a right game with delivery companies reliability at the moment so they never arrived sadly :(

Either way it's done now and i'll be looking forward to a stereo upgrade next I think. Need to get a decent double DIN DVD player which can link upto the rear view camera and the Alpine screen in the back. I guess an audio pumpkin may do it as the one I have at the moment's one of those cheapo dodgy Android things anyway but i'd definitely like to get something with android auto on it this time.

May also be on the lookout for a decent Nissan Cube now too if one come up at the right price to use as a 2nd vehicle.
 
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