E51 The E51 Catalytic Converter Problem

Karl

Founder
Staff member
E50 Owner
Premium Member
E50 Expert
#1
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

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 problem. Through use, after heating up and cooling down, they start to deteriorate. This happens with ANY 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 2 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.

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.

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.
 
Last edited:

Adam Bracher

Newbie
E51 Owner
#2
Hi All

New to the forum as need some advice really. Have had E51 since last June but been off the road since December as it began spluttering and then just died. Couldnt get it started again and had it towed away. The garage has spent last 6 months looking at it periodically and dont know what is wrong with it. They have got it going again, drive it, gets seriously hot, load of smoke out of the exhaust and thats that. Then i see the past above and i wonder if that could be it. Before the cats get blocked, would there be shuddering and lack of response? I think I will point the above post out to them.

The mechanics said that there is excessive fuel getting into the system but they dont know where it is coming from. I know i havent given too much info here, but any advice would be greatly welcomed as only drove it for 5 months and now been off road for 6!
 

MrRob_in

Part of the furniture (please de-cat your e51/2)
Staff member
Premium Member
E51 Expert
E51 Owner
#4
Hi All

New to the forum as need some advice really. Have had E51 since last June but been off the road since December as it began spluttering and then just died. Couldnt get it started again and had it towed away. The garage has spent last 6 months looking at it periodically and dont know what is wrong with it. They have got it going again, drive it, gets seriously hot, load of smoke out of the exhaust and thats that. Then i see the past above and i wonder if that could be it. Before the cats get blocked, would there be shuddering and lack of response? I think I will point the above post out to them.

The mechanics said that there is excessive fuel getting into the system but they dont know where it is coming from. I know i havent given too much info here, but any advice would be greatly welcomed as only drove it for 5 months and now been off road for 6!
Sounds like a typical example of what happens when the cat system totally blocks. Unfortunately. Sorry we didn't get the message to you in time.

Imo don't waste any money on buying parts or anything else for this car until you know he engine isn't damaged (it is unlikely to not to be damaged tbh) once the blockage has been removed. Get the garage to split the exhaust between the cats and see if it runs ok and doesn't burn oil first.
 

Alan Morgan

Here for life
Premium Member
E51 Owner
#5
Pretty much covers it!

Only thing I would add is on the legal aspect, you really should inform your insurers of this - as sensible a modification as it is, it is still a modification and it would more likely be viewed as a performance mod than cosmetic...
I'm not disagreeing about the theoretical legitimacy of telling the insurance company about de-catting but why open Pandora's box? If you de-core rather than de-cat, then the work isn't even visible let alone detectable (other than by dis-mantling).
 

MrRob_in

Part of the furniture (please de-cat your e51/2)
Staff member
Premium Member
E51 Expert
E51 Owner
#6
I'm not disagreeing about the theoretical legitimacy of telling the insurance company about de-catting but why open Pandora's box? If you de-core rather than de-cat, then the work isn't even visible let alone detectable (other than by dis-mantling).
'It's normal preventative maintenance... go look on the owner's club site' ;)
 

Alan Morgan

Here for life
Premium Member
E51 Owner
#7
Hi @MrRob_in, the reference to Pandora's box is in respect of telling the insurance company, not the cat work which I had done within weeks of getting my Elgrand (and that was down to the info on here from the likes of yourself and others). For less than the price of a service, even if you're a doubting Thomas, why would you not get the work done. After all people spend many hundreds of pounds on insurance against other possible events, and this can be seen in a like manner.
 

MrRob_in

Part of the furniture (please de-cat your e51/2)
Staff member
Premium Member
E51 Expert
E51 Owner
#8
That is fair enough but a stealthy decore is only one way of dealing with the problem. I didn't think this thread was aimed at those so experienced.

Nothing theoretical about it anyway. Yes the cat problem does exist and there are ways of sorting it. Personally, I wouldn't want to encourage something that may cause further problems to people who may not understand the possible consequences.

If the worst should happen, it is detectable even if dismantling is necessary. Unlikely to happen? Absolutely. Would I want it on my conscience that someone listened to my theoretical advice off the internet?

Insurance is a complete rip off anyhow, I wouldn't bother with it ;)
For the record I told my insurance co. They noted it just like tow bar, non oe but Nissan alloy wheels, Nissan Aero bib bonnet aero kit and airbags in rear suspension... no change in premium.
 

SQUIZ

Member
Premium Member
E51 Owner
#9
Pretty much covers it!

Only thing I would add is on the legal aspect, you really should inform your insurers of this - as sensible a modification as it is, it is still a modification and it would more likely be viewed as a performance mod than cosmetic...
Do you reckon i should inform my insurers that i have swapped out my radio,changed a wheel bearing ,waxoiled my Elgrand and ordered an extra keyfob ?Is it possible that my insurance is now invalid because of the work i have carried out.OH !! i forgot to mention that i used a liquid cleaner on the inside and have started to use a clay bar on the exterior paint,the clay bar is being consumed by the paint so therefore this could make the vehicle NOT AS STANDARD
 

SQUIZ

Member
Premium Member
E51 Owner
#10
[COCKQUOTE="blingo, post: 48053, member: 219"]Absolutely, you should ring them immediately! I honestly can't believe you have admitted to all that on a public forum, they are probably voiding your policy right now. You might get away with a couple of those mods if you are really lucky. It obviously depends on whether the keyfob still has the original battery. And as everyone knows, the claybar use is very much an insurance grey area - depends entirely on what lubricant you used. I suspect you might be using an unapproved one if the bar is being consumed by the paint though.

You know what is actually funny? That you can't see the difference between any of these things and removing the cats.[/QUOTE]
Ah !!! You are telling me what i maybe able or unable to see.Are you an optician who doesn't need to measure peoples vision physically before diagnosing sight problems ? Please advise on exactly what or how one may invalidate their insurance by looking after their vehicle , whether it be cosmetic or to prolong the life of the vehicle,whether mechanical or cosmetic .ie.if a vehicle manual states semi synthetic oil and one uses a higher grade fully synthetic oil will this invalidate insurance ? T
 

Travellingman

Well-Known Member
E50 Owner
Premium Member
#11
anything that was not fitted by the original manufacturer is a modification , tow bar , fancy stereo , conversion to camper , ie , sink , cooker , fridge , a decat is a modification , so , if you prang it and the insurance company find its got a cat or 2 missing then your up cat creek without a paddle , washing it , detailing it , hoovering it , are not mods .they are just things you do when you should actually be driving it .
 

LLGrandJ

Admin / Disc Jockey
Staff member
E50 Owner
Premium Member
#14
Can I just double-triple-check this doesn't apply to E50s with the VQ35DE engine? The wiki seems to suggest it does...
 

Travellingman

Well-Known Member
E50 Owner
Premium Member
#15
Blatantly obvious , If I do it its fine , If someone else does it its questionable , If the Law says it its Optional , If a Mate says it its Gospel Truth , If the Wife says it its Mandatory , If a non driver says it its Crap , Facts discussed in a Pub are much more Scientifically Correct than any Info from Stephen Hawking or that Einstein guy , If an Insurer says the answer is Modified then maybe you shouldnt have asked the Question in the First place ?
plead ignorance and just say it was Foreign so you thought it was a "standard fitting "
 

Karl

Founder
Staff member
E50 Owner
Premium Member
E50 Expert
#16
Can I just double-triple-check this doesn't apply to E50s with the VQ35DE engine? The wiki seems to suggest it does...
No, the cat issue does not affect the E50 as the E50 only has a dual cat system, not a quad cat system.

As for the rest of this thread, what a pointless debate it is.

Yes, if you remove or de-core the cats, this is a modification that needs giving to your insurance company. This is a modification to the original design specification of the vehicle itself.

Yes, you should also tell your insurance company if you are using bulbs or oils that are NOT recommended by the manufacturer. But in the event of a crash, they are not going to test your oil to see if they can determine a brand and oil type. They will, however, check for common modifications to get out of paying out. Insurance companies know that people remove cats for performance reasons... they also know they get de-cored. Just because we happen to be doing it to prolong the life of our cars, other people with other vehicles do it for performance reasons. As such, cats ARE a hot topic for insurance and something they most likely WILL look into in the event of an accident.
 

blingo

Well-Known Member
Premium Member
E51 Owner
#17
No, the cat issue does not affect the E50 as the E50 only has a dual cat system, not a quad cat system.

As for the rest of this thread, what a pointless debate it is.

Yes, if you remove or de-core the cats, this is a modification that needs giving to your insurance company. This is a modification to the original design specification of the vehicle itself.

Yes, you should also tell your insurance company if you are using bulbs or oils that are NOT recommended by the manufacturer. But in the event of a crash, they are not going to test your oil to see if they can determine a brand and oil type. They will, however, check for common modifications to get out of paying out. Insurance companies know that people remove cats for performance reasons... they also know they get de-cored. Just because we happen to be doing it to prolong the life of our cars, other people with other vehicles do it for performance reasons. As such, cats ARE a hot topic for insurance and something they most likely WILL look into in the event of an accident.
I really didn't want to start an argument and have deleted my posts. Was only trying to help.

SQUIZ was actually right, I am a cock. And if treated like one, I have a habit of becoming a bigger cock. But it isn't helpful and promise not to get drawn in to it again.

The only reason I brought it up in the first place was because I thought some people wouldn't realise that it is something that insurers do look out for.

As you said, pointless. In all honesty, I briefly considered a "rage quit" on here.

Fortunately I do see the value of what we have here and the knowledge that others have. More importantly, I'd be f**cked without it :)

Sorry, will take more than some smart arse comments to get rid of me.
 

SQUIZ

Member
Premium Member
E51 Owner
#18
I really didn't want to start an argument and have deleted my posts. Was only trying to help.

SQUIZ was actually right, I am a cock. And if treated like one, I have a habit of becoming a bigger cock. But it isn't helpful and promise not to get drawn in to it again.

The only reason I brought it up in the first place was because I thought some people wouldn't realise that it is something that insurers do look out for.

As you said, pointless. In all honesty, I briefly considered a "rage quit" on here.

Fortunately I do see the value of what we have here and the knowledge that others have. More importantly, I'd be f**cked without it :)

Sorry, will take more than some smart arse comments to get rid of me.
AN APOLOGY TO BLINGO
No you are not a cock,both you and i got drawn in by each other.I personally felt protective towards Sir Robin .who has so kindly put his efforts into helping people realise the CAT ISSUE. HANDS UP i was a cock too,so would like to push this one under the bridge. Sorry if we didn't see eye to eye but hey life is too short for arguing. I have respect for every person using this forum and for every Elgrand owner.Sorry if we got off on the wrong foot .
 

blingo

Well-Known Member
Premium Member
E51 Owner
#19
AN APOLOGY TO BLINGO
No you are not a cock,both you and i got drawn in by each other.I personally felt protective towards Sir Robin .who has so kindly put his efforts into helping people realise the CAT ISSUE. HANDS UP i was a cock too,so would like to push this one under the bridge. Sorry if we didn't see eye to eye but hey life is too short for arguing. I have respect for every person using this forum and for every Elgrand owner.Sorry if we got off on the wrong foot .
Apology accepted!

You are still wrong though...






I am a cock :)