I *may* need to replace the catalytic converter in my 11 year old Nissan Micra. I have seen some very good prices but also read that aftermarket cats do not contain precious metals and do not last nearly as long.
I know about running the car at high revs for 20 minutes to try to clear the cat and so far this has been successful.
I am wondering if it is possible to recondition a catalytic converter or to buy a quality unit cost-effectively. I'm guessing that going to a scrapyard would be illogical as the cats there would be about as old as mine is.
I've never heard of a catalytic convertors needing that treatment nor of any engine managemnt system that tells you the catalytic convertor has been killed. They get killed by unburnt petrol or lead, your not likely to notice untill the car fails the MOT emmisions test. But as my last petrol car was about 15 years ago things in that world may have moved on...
DPF's on the other hand do need the occasional "good run" to burn the caputured muck out of them and the engine management system may indicate when this is required. Normally only required if the car is only used for short stop/start journeys.
It's just contingency planning at this stage. My concern is that if the cat fails catastrophically the car will not pass its MOT.
P0420 code stands for ?Catalyst System Efficiency Below Threshold (Bank 1).? When you receive a P0420 code it means your catalytic converter is not operating at maximum efficiency. Usually this means your catalytic converter needs to be replaced or there is a problem with your O2 (oxygen) sensors. Source:
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Yes, but what form does this morbidity take? Is it a case of the passages becoming blocked or are the precious metals stripped away?
What about diesel particulate filters? Why do they need to be replaced? Is it simply that not all the soot is burned off during a high-speed longer journey, and so it gradually accumulates? Or does something in the DPF gradually age?
I hope I don't have to have my DPF replaced again in the lifetime of the car, because it cost about £1000, but then half that was the cost of a new cat because a thread on the cat that a pipe between DPF and cat screwed onto got a stripped thread as they were removing the DPF, and the only remedy was a new cat. I was told (and in light of what people have said in this thread, I wonder whether I was being told porkies) that the cat was "about due for replacement anyway" - I wonder if that was just to make me feel better about having to have a new one.
As with so many things in life, the car is worth a lot more to me as a working car than its second hand value (which was about £200!) so I stumped up for the work rather than sell it to the garage as an MOT failure (no DPF and cat means automatic failure...). And after that "little" job, the car still goes like a bomb, at 11 years and 190,000 miles old.
Probably a daft question, but what gases does a cat convert in the case of a diesel? In a petrol, it's oxidising CO to CO2, but since diesels burn the fuel more completely, there will be virtually no CO. Do diesel cats do anything to mitigate the amount of NOx by reducing it to N and O?
You can fix stripped threads using helicoils, if you can get to them. Typically the hardware to do so is about £5 but you need a tap and drill and if its stainless steel many garages just won't have the stuff.
I think the problem that the garage had was that the thread stripped in such a way that they could not get the nut off to use a thread-cutter, nor could they retighten it so it was gas-tight. I suppose hacksawing the nut at the
12 o'clock and 6 o'clock positions to separate it into two halves would have a) been labour-intensive (ie costly) and b) risked damaging the thread beyond the repair of a helicoil.
Anyway, I got a new cat as well as the new DPF I'd budgeted for.
I suppose, given the age of the car, there are a lot of expensive repairs that I've not had to pay for yet: clutch, shock absorbers, turbo. I've never had a car before that's still on its original clutch after 190,000 miles. OK, the bite-point is getting a bit high (presumably the auto-adjuster has got the end of its adjustment range) but there's no hint of slippage, even when I had to do a hill-start on a 1:3 hill when the guy in front of me stalled and then started rolling backwards towards me ;-)
I lost count of the number of exhaust manifolds on FIATs (my dad specialised) that I saw with 3, 2 or occasionally just 1 of the 4 studs that should hold the downpipe on. SOP for everywhere else was to put an air wrench on, bang, and "oh dear ...."
Of course once you had broken the stud flush to the cast iron manifold you were pretty f***ed.
Best ones were from Kwik Fit, who had no choice but to pay the £200 or so (plus VAT) for us to repair it.
The secret was to use oxy-acetylene to make the *brass* nuts red hot, and they'd slip off easy. If the stud was over corroded, once you removed the nut, you made it red-hot and used a stud remover to gently remove it, and then replace with new studs, proper *brass* nuts, and locking plates.
(See also: snapped brake bleeders on calipers ....)
And yet whenever a customer felt like trying to beat us down on price, they always had a relative who was an expert because they worked at Kwik Fit ....
Those of us who are of a certain age, can remember when Kwik Fit were just tyre fitters (exhausts came later). They couldn't even get that right, and a couple of times we had a call from our local one because a customer had a Strada (which had a closed rim) and they didn't know how to change a tyre on one (despite having a machine to do it).
But then PCWorld are "experts", so are Curries. Comet were ... etc etc.
I don't have acetylene. But have never had a stud snap where a brass nut is in place. Steel, often.
Hope you don't think I was saying replacing brass nuts with steel is good practice? No idea why they often do this - perhaps losing the brass ones. And steel is much cheaper than brass.
How good any outfit is depends on the individual fitter. And there are cowboys around everywhere.
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