Urgent help please - melted cat!

Good morning all,

I am in need of some fairly urgent advice regarding the exhaust system on my 2011 1.6Tdi Monte Carlo.

I have had a noisy exhaust and fumes in the cabin, took the car to the garage and found a hole melted through the back of the cat. The cat is a replacement from a salvage yard and was to replace the original, which had a broken flexi pipe.

My question is, what is likely to have caused the cat to melt through? I don't want to replace the exhaust, if there is another underlying issue.

The back box is pretty well corroded and it is possible that it is partially blocked, would this cause the cat to melt? Why would the original cat not have melted if this were the case?
Is it most likely the second hand cat was already FUBAR'd?

I would say that the car runs a bit lumpy at low throttle in particular, but this could be a number of things. I did wonder about injector issues, but to cause this within only a couple of weeks of driving with the replacement cat, it would seem unlikely.

Your thoughts and advice would be greatly appreciated.

I would say it has a blocked DPF, we welded in new flexi joints. What is the VIN?

TMBFL25J2B3193204

This has a hole at the back of the cat, the flexi and DPF unit upstream look to be intact. Would a blocked DPF cause the cat to burn through?

Attachment 38894

According to ETKA using the VIN, the car should not have that setup, the CAT and DPF are all in one, part number 6R0 254 700 NX for the genuine exchange unit.

https://cdn.pkwteile.de/thumb?id=187...e&ccf=94077835

This is something that came up before, when you advised me on the part numbers for the EGTs.
The exhaust looks original and presumably there is no way to fit the wrong system by mistake, or is there?
The system that you linked to is actually a cheaper option and I'm wondering if it would in fact be possible to fit this instead?

On my system, there is one DPF pressure hose, it is connected after the DPF and before the cat, although there is another hose (there has to be), it is a short one of about 100mm and is open to ambient pressure in the engine bay, it isn't connected to a pipe on the DPF.
If the alternative system that you linked to can be retrofitted, that would be ideal, as it seems more widely available.

I see now, the ETKA pic is left hand drive, your design is right hand drive specific. Yes a blocked or damaged DPF could cause temperatures of circa 900 centigrade; in some parts of the workshop info it says "caution, vehicle may burn down"

https://live.staticflickr.com/65535/...240197c7_o.jpg

Pre-exhaust pipe with diesel particle filter, vehicles with right-hand drive - Summary of components
(Fabia II, Roomster)

1. Lambda probe -G39-, 50 Nm the thread of new lambda probes must be coated with assembly paste, for a re-used lambda probe, only coat the thread with hot bolt paste -G 052 112 A3- the hot bolt paste -G 052 112 A3- must not come into contact with the slots of the probe body
2. Gasket, replace, Check fitting position
3. Warm-type clamp, 7 Nm, replace
4. Exhaust gas temperature sender 4 -G648-, 45 Nm, the thread of the new temperature sender must be coated with assembly paste, grease only the thread with hot bolt paste -G 052 112 A3- for re-used temperature sender.
5. Exhaust gas temperature sender 3 -G495-, 45 Nm, the thread of the new temperature sender must be coated with assembly paste grease only the thread with hot bolt paste -G 052 112 A3- for re-used temperature sender.
6. Support for differential pressure indicator -G505-
7. Clamps
8. Control line
9. Differential pressure sender -G505-
10. 4.5 Nm
11. 25 Nm
12. 25 Nm
13. Support, screwed onto the cylinder block
14. Catalytic converter with diesel particle filter

I take it that the first system you linked to, isn't going to be compatible?

Which part of the system is the DPF and which the cat? Also, your diagram shows two DPF differential pressure pipes on the back box, suggesting that this is the DPF, but mine has only one at the front of the back box and the other is open to atmosphere, so looks like the DPF is the oval can at the top. I have to say, this is the first time dealing with DPFs and I'm not enthused so far.
I might very well never buy another diesel.

The cat is first, then the DPF. I hate small Diesels full stop, crime against humanity inflicted on society by marxist eco nutters.