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LIST OF ACTIONS REGARDING E51/E52 CATALYTIC CONVERTER ISSUES

ircooper said:
What is the first thing folks notice when the cats go?
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The cats can fail in various ways. They can melt in which case they may stay as a single lump (as opposed break up) but after melting they'll block the flow of exhaust gas. They can crack and break up in which case the debris may just move further back in the exhaust and not cause a blockage, or can cause a blockage.

The worst situation is when they break up and cause a blockage because then there's ceramic dust from the cat material stuck in the exhaust, the exhaust gets pressurised and cat dust can get back into the engine where it acts like a grinding paste.

E51's have 4 cats (2 each side of the engine). It is the front cats that fail. People used to decore rear cats so that in the event front cats broke up and debris did move back in the exhaust there would be no rear cats for the debris to block.. but that wasn't totally safe because front cats can fail in a way in which they block themselves up in which case regardless of whether rear cats have been decored cat dust would still get back into the engine. Decoring rear cats has saved many engines, usually without the owner even knowing front cats have failed, but there are unlucky people who have had rear cats decored but front cats failed and blocked themselves up (or at least front cats failed in such way, perhaps with a temporary blockage, that saw cat material enter the engine anyway).

If cats are blocked the exhaust gas can't escape, so the engine cylinders remain at high pressure even into the intake strokes, which prevents the engine sucking in new air, so the driver might notice the engine is down on power. A cat failure / blockage will usually occur on one side of the engine (one cylinder bank) and the side with the blockage will get less fresh air than the side without the blockage, so the engine ECU 'sees' that one side of the engine is needing more fuel than the other side and interprets this as a cam timing problem so triggers cam related OBD error codes.

If cats break up the debris can cause a rattle from the exhaust.

I did a thread on how to use OBD live data to gain insight into cats status https://forum.elgrandoc.uk/threads/...-using-obd-live-data-readings-outlined.23518/
 
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Blippi said:

👍😜
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It's unlikely that would fit between the exhaust manifold and front cats, if it could be done I reckon a completely different exhaust would need to be fitted to make it fit anyway.

Nevillerover said:
Reckon the labour will be expensive tho.
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Would think labour ad parts would be expensive.

Would expect it to cost less to keep the standard exhaust but decore cats and convert to LPG, with an LPG conversion you don't need any cats to be legal and pass MOT and emissions are cleaner than petrol even with cats.
 
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Sorry not reading 11 pages to find out if E52 2011 3.5 is actually related to this topic or not
 
I've not heard of any E52s suffering in the same way. However this may be because
a. there's far fewer E52s in the UK
b. those that have been imported are much younger than most E51s here.
As I see it any system where there are two cats in line will be susceptible. RAC/AA put a life expectancy on cats off 100k miles or 10 years. The front one does the vast majority of the work and will therefore break up first. The rear one will most likely then get blocked by the debris from the front one.
If I had an E52 I would look to safeguard it by dealing with the rear cats before any problems arise. Others may well accept the risk and have many happy years of cat-trouble free motoring.
 
JohnK said:
I've not heard of any E52s suffering in the same way. However this may be because
a. there's far fewer E52s in the UK
b. those that have been imported are much younger than most E51s here.
As I see it any system where there are two cats in line will be susceptible. RAC/AA put a life expectancy on cats off 100k miles or 10 years. The front one does the vast majority of the work and will therefore break up first. The rear one will most likely then get blocked by the debris from the front one.
If I had an E52 I would look to safeguard it by dealing with the rear cats before any problems arise. Others may well accept the risk and have many happy years of cat-trouble free motoring.
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Thank you I'll add that to my to do list, I take most people just get a section of pipe welded where the rear cat was? Or can you knock out the interals
 
Abarth_1200 said:
Thank you I'll add that to my to do list, I take most people just get a section of pipe welded where the rear cat was? Or can you knock out the interals
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On the E51 you can either take the cat out completely or just decore it. Assume 52s the same.
 
I believe the E52 is a 3 cat system...I'm sure I read it somewhere...maybe wrong lol.
 
Reverend RobP said:
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.
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Good work 👏
 
Looking for my first Elgrand. This article and all subsequent posts contain very useful information. Thanks everyone.
 
If you get the front cats recored does it cause an issue with the emissions sensor which is just after one of the front cats? Option 2 is my preferred choice but concerned it will throw up fault codes
 
mkelly123 said:
If you get the front cats recored does it cause an issue with the emissions sensor which is just after one of the front cats? Option 2 is my preferred choice but concerned it will throw up fault codes
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My fronts are decorred, gone through 2 mots now without issue
 
mkelly123 said:
If you get the front cats recored does it cause an issue with the emissions sensor which is just after one of the front cats? Option 2 is my preferred choice but concerned it will throw up fault codes
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Lots have reported no issues but some have had emissions problems after front decore , hard to tell without lots of evidence but could be down to a combination of of things
After reading and debating this the whole time I’ve been in this club I’ve decided to replace fronts ( in my case it will be stainless not ceramic) and replace rears with de cat pipes , should last the lifetime of the bus
 
mkelly123 said:
If you get the front cats recored does it cause an issue with the emissions sensor which is just after one of the front cats? Option 2 is my preferred choice but concerned it will throw up fault codes
Click to expand...

It doesn't cause any issue with the emissions sensors (lambda sensors). The main lambda sensors are between the engine and any of the cats, the ECU uses signal from these main lambda sensors to keep fuel mixture correct. The lambda sensors between the cats don't have much effect on anything on E51's, on some vehicles the ECU would use lambda sensors in a similar position to check the cats were working (and I can read live data from them to check if front cats are working) but on Elgrands no problems will be flagged even if front cats are gutted.

Emissions is a slightly different subject, they will be higher without front cats fitted but many Elgrands have passed MOT emissions tests with front cats gutted and rear cats intact.

Running on LPG you don't need any cats fitted for an easy MOT emissions pass. This is because the MOT emissions test for LPG vehicles allows higher emissions while at the same time emissions from the engine are lower running on LPG because it burns a lot cleaner, so there's the double effect of an easier standard and cleaner emissions in the first place. Some owners have had me convert their vehicle to LPG primarily so they could decore all 4 cats and easily pass the emissions test... Rather than spend a similar amount of money fitting different aftermarket exhaust parts they spent the money on an LPG conversion which also has the benefit of allowing running on cheaper fuel while keeping the full unaffected ability to run on petrol as normal if they don't mind paying full price for fuel, also gives double range between refuelling if the owner doesn't mind paying full price for fuel for half of that range. Heh, but regardless of the reason for converting to LPG, owners with the ability to run on LPG will always prefer to run on LPG instead of petrol because it is cheaper and keeps the engine oil a lot cleaner.
 
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