LIST OF ACTIONS REGARDING E51/E52 CATALYTIC CONVERTER ISSUES

[Nevillerover]

Reckon the labour will be expensive tho.

 

[Lpgc]

What is the first thing folks notice when the cats go?

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/

 

[Lpgc]

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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.

Reckon the labour will be expensive tho.

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.