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E51 The E51 Catalytic Converter Problem

Remove the small one, if you can see through it they've been done, if you can't they haven't.
 
Winchester said:
True, I’ve seen this several times.
Click to expand...
Hi Adrian,
It has been suggested more than once that the presence or otherwise of the secondary cat 'core' could be determined by the temperature of the cat box after warm-up - I think the 'test' went something like this:
> If the cats HAD NOT been de-cored then the rear cat box would be significantly hot (as the cats did their work) than the entry and exit pipes.
> If the cats HAD BEEN REMOVED, the rear cat box and entry/exit pipes would be of a similar temperature

Given that you see and deal with a good few cars/clients for this issue, due you have any views on the abov please?

One suggestion is that the temperatures could be measured using an infra-red thrmometer - is this probably do you think?

Cheers, AlanM
 
The easiest way to see if you got cats or not is to go for a run for half an hour comeback parked the vehicle up and have a cup of coffee half-hour later go out and touch the exhaust pipe it might still be warm then be careful touch the cats if their hot the cats are still there just be careful they still could burn your hands when I have mine removed a hour later still couldn't touch the cats.
 
AlanM said:
Hi Adrian,
It has been suggested more than once that the presence or otherwise of the secondary cat 'core' could be determined by the temperature of the cat box after warm-up - I think the 'test' went something like this:
> If the cats HAD NOT been de-cored then the rear cat box would be significantly hot (as the cats did their work) than the entry and exit pipes.
> If the cats HAD BEEN REMOVED, the rear cat box and entry/exit pipes would be of a similar temperature

Given that you see and deal with a good few cars/clients for this issue, due you have any views on the abov please?

One suggestion is that the temperatures could be measured using an infra-red thrmometer - is this probably do you think?

Cheers, AlanM
Click to expand...

When customers turn up for a decat their exhausts are always really hot, my service is to swap them over as soon as possible so I get the first one off straight away. So I don’t know how an infra-red would help?
 
Winchester said:
When customers turn up for a decat their exhausts are always really hot, my service is to swap them over as soon as possible so I get the first one off straight away. So I don’t know how an infra-red would help?
Click to expand...
I think what @AlanM is alluding to is that if you want to know if your cats have been removed or not, a way to tell would be to use an IR thermometer to determine whether the cat section is significantly hotter than the rest of the exhaust system.
 
Any benefit to ripping the cats out and going single high flow cat either side instead? You think it will throw a CEL?
 
I had my front cats replaced with 200 cell sports cats set between the original front and rears and the rest ripped out (centre box, no rears and all pipes)

Edit: new centre box!
 
Last edited:
Anyone heard of VQ25 cat issues? Or is that EOC myth that all E51 with 4 cats fail...
 
Any car with a secondary cat setup can suffer blocked rear cats when fronts fail, not just Elgrands.
 
As a total Elgrand noob, it's threads like this that make forum membership so worthwhile. Thanks guys and gals for sharing your knowledge and experiences.
 
Thanks for this information guys, will use this when I get mine
 
Lize said:
Any car with a secondary cat setup can suffer blocked rear cats when fronts fail, not just Elgrands.
Click to expand...
But most cars don't have such a setup and perhaps for the obvious reason lol.
 
E51's seem unlikely to throw a code with cats removed, even if they did it would be because of post cat sensor readings not pre-cat sensor reading, which wouldn't effect actual fuelling.
 
Does this issue affect all E51's, 2.5l and 3.5l engines?
 
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