UKC

Just had an MOT failure for diesel emissions on my Berlingo HDi. The inspector told me (in french - may have misunderstood!) I should cut open the middle exhaust box, clean out the collector and reweld. We recently acquired a 2nd car which does all the longer journeys so the Berlingo hasn't been getting a good blast on the motorway. It also exhibits low pulling power - both point to an exhaust problem.

So what to do - will it cure with a dose of fuel additive and a blast up the autoroute ? Part of my dilemma is identifying which actual box in the system is the acting dpf - none of the web pages I search commits - anyone know? The front box is named as a catalyseur - which some say can become blocked; is this one and the same as the dpf ?

To compound confusion I found another web page which says dpf's block with soot *and* ash - the product of 'burning-off' - and use of fuel additives; maybe I'm getting too complicated here ...

In reply to LeeWood:

Not an expert but from what I understand, there will be a catalyst and a DPF in separate casings that may be within the same section. I didn't need it done but there was some jiggery pokery on the exhaust on my last car where a flexible section at the front failed and it would have been £2,000ish to replace that section as it had the catalyst and DPF in it... garage managed to repair the flexi bit but also told me that if worst came and DPF needed repaired the bodge/borderline (il)legal method is to remove pipe, cut open DPF at top and remove contents, weld back together and replace.... the cutting can't be seen as its between the pipe and car underbody. You then had to get an engine re-map so that engine management workes properly in absence of the DPF... effectively he would have sourced a new 'chip' for the car which would probably have boosted power and improved economy a bit as side effects.

In the UK I think all that is technically illegal but as the MOT requirement is nothing more than a visual check externally that the DPF appears to be present (i.e. the casing is there) people can and do go down this route.

So - I think you can do it, but there may be an extra stage (the engine re-mapping) that you haven't picked up on or been told about. Engine re-maps vary from 30 or 40 pounds for a dodgy download that may well not work or may do something dangerous to 3 to 500ish for 'reputable' ones. But even those have many people who think you shouldn't be messing with manufacturer settings.

In reply to Ferret:

Thanks that makes for good reflection. I'm thinking the named regeneration process could not work so efficiently in the central box - as it needs heat - dissipated down the pipe after the catalyser ie. prob as you say dpf combined in box nearest engine.

But I wasn't thinking to cheat on having one - and unaware that there's any such engine control software in our diesel engine; - I thought only petrol engines had these ?

In reply to LeeWood:

I had a similar problem with dpf clogging and faced a £1000+ Bill to replace it. I asked if we could just cut it out. They said they couldn't suggest that but now that I've mentioned it, yes they could. Had dpf cut out rewelded, ecu reprogramming and ended up with 20+ more bph and better economy for £250... winner all round (apart from atmospheric polluting nano particles). Passes mot emissions every time, no regeneration cycles needed ever again

In reply to LeeWood
The DPF is easy to identify as it will have two small pipes going in to it, to monitor pre and post pressure to calculate diffrential pressure, and two wires at either end to monitor pre and post temp..
The catalyst and the dpf can also be combined in to a sinlge housing on some vehicles.
It is unlikey that the vehicle has failed for the dpf or catalyst as the emsssion test for diesels does not test belive it or not! either the gasses managed by the catalyst or the particualte matter from the particaulte flter.
The test they perform is an Opacity test and would only pick up things like problems with oil being burned or fuel being burned at low temperatures causing smoke.Not particulate matter from the filter, or hydrocarbons,Co2 or carbon monoxied from the catlyst
Before detstroying what could be a £1000 pound componnet which is what is being suggested i would look elsewhere first.
Dan.

In reply to DANNYdjb:



The OP would appear to be in France: the local equivalent of the MoT test may be more stringent than ours, I don't know.

Nonetheless, I would agree that the solution is probably not the complete removal of a component which is required for the vehicle to pass emissions type approval in the first place, and which is there to reduce the amount of carcinogenic particulate pollution which the engine throws out in to the air that we all (even French people) have to breathe.

If the OP is indeed in France then I think he might find it relatively straightforward to locate a garage which is knowledgable able Renault vehicles, their quirks and quiddities...

In reply to LeeWood:

You can do a DPF regen with any good diag tool, failing that a long runat constant high revs ie motorways in 4th at 70 . Normally works on 1st/2nd regen
Have lots of issues with customers vehicles at work who dont give it a good run every now and then

In reply to LeeWood:

Have you tried giving it the classic Italian tune up? Apparently you need to run it at high revs continuously for a while (8-10 min) without lifting off the throttle to trigger the ecu to go through a regeneration cycle.
Most exhaust based problems seem to require similar treatment.
Google images should give you an idea of what they look like.

In reply to LeeWood:

If it's chucking black soot out the back when changing gear you might be driving it too sedately. I totally cleaned my system out by driving it into 3.5k+ revs on every gear change, and sitting in 2nd for longer periods. My fumes went from turning the ground black to fairly clear. Not sure if this is practical though if you need a very quick MOT done though as it takes some driving.

In reply to Martin W:

The tests are very similar all around europe.
The point is not the stringency of the test but the method of testing.
The machines used in europe are the same machines used in the UK.
Currently the coefficients in use in any of the machines are not capable of anlayisng the particulate matter.

Thanks to Vw this may all change as we are now looking at achieving greater accuracys in equipment..
There is discusion at the moment as to wether the current machines could meaure relaibly down to the neccesary value, or new machines using light scatter technology would be better.
Sorry To Bore.

Dan.

In reply to ALL:

Thanks for all responses. yes I am in France and no there is no ECU (does any diesel motor have one?) I'll risk a good burn up before the re-test. I have no intention of cheating on the environment - but perhaps then I should not have a diesel engine ...

In reply to LeeWood:

can you see smoke? is it lacking power? might be worth disconnecting the MAF sensor? (i'm no expert mind)

In reply to LeeWood:


I'm quite certain it will have an ECU, pretty much every vehicle on the roads these days will have an ECU. This would control engine timing and fuel injectors at an absolute minimum, and probably monitors air flow, crank case pressure, oil pressure, temperature, emissions etc etc.

In reply to LeeWood:
As others have said, give it a long run at high load, it will need heat to burn off any soot that is in the DPF.

You also mention using possibly using fuel additives as a possible cure - it shouldn't do any harm but I don't think it will directly fix the problem. Diesel emissions are very sensitive to the quality of the fuel injection process. Over time the injector will get clogged up and blocked by soot and the fuel spray changes into more of a dribble (a slight over exaggeration but it give you an idea of the process). This produces rich areas of fuel that cannot burn properly and product soot, running some fuel additive injector cleaner should clean the injectors which will produce better combustion giving less soot and better performance. It is worth noting that most branded fuel (ie Esso, Total etc) typically has some additives / detergents in it already, it is this more advanced mixture that means it costs more than super market fuel (which typically does not have any additives), and it is a good idea to run a tank of 'nice' fuel every now and again as standard. Also, I know that some car manufacturers now specify the addition of injector cleaner to a tank of diesel as part of a standard service. So, although not a direct fix for a blocked DPF, its not a bad idea.

Possibly of further general interest, some newer diesels have an extra fuel injector straight into the DPF to generate really high temperatures to clean the filter.