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Old 22-09-2012, 11:18 AM   #23
Rodge
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Join Date: Feb 2010
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Default Re: Diesel Particulate Filter Problems

Well our DPF kept clogging up, which I didn't know about because there is no warning device on 2007 MBenz diesel's. The sensor in the DPF kept sending the ECU signals to do late stage fuel injection to trigger a regeneration, (burn-off cycle) but the exhaust never got hot enough to achieve this and all the late stage fuel injection resulted in heavy over-fuelling of the engine, and unburned fuel making its way down into the crankcase.

The oil level went UP at the rate of 1 litre on unburned diesel getting into the crankcase oil every 3,000 km's.

Naturally I had some interesting discussions with Mercedes-benz about this and no they did not play nice, I had to make it quite clear that my lawyers number was on my speed-dial.
I hear stories of diesel cars having their oil changed and the oil being changed-out being substaintially higher than the official rated crank-case capacity so this non-sense is still going on.

DPF's can generally be removed but yes the cars ECU needs to be re-programmed and it took M Benz 2 attempts to get it right. They took considerable convincing to agree to this proceedure.

What concerns me is that it appears that even many years after these dreadful filters were first fitted customers are still being sold vehicles and not being told of the DPF's operational requirements, either through ignorance on the part of salesman or worse, a deliberate concealment of important customer information.

Yes I agree its very, very hard for city residents to find the time and space to achieve 80 k.p.h. runs for 20 minutes or more. This could involve having to "create" lengthy motorway trips each week, late at night when the roads are relativly free of congestion, for no other purpose than just to allow for a proper burn-off of the DPF. This is hardly a satisfactory situation I would have thought and burns more fuel.

Mum's taking diesel vehicles on the short school / cafe / soccer / shopping runs are wide open to expensive highly problematic issues as are people who commute short distances. Be careful people, don't get caught with a vehicle that's not suitable for intended purpose.

Questions to ask the salesman...and don't stop asking until you are sure you've got the correct answer.

1. Does this vehicle come with a DPF ?
2. What warning device is fitted to the vehicle to warn the driver when the DPF is getting full ? Please show me where this is.
3. How do I go about achieving a good re-generation cycle for the DPF ?
4. Is the DPF covered in the manufacturers warranty ? Please show me the paperwork and specific clauses pertaining to warranty coverage of this item.
If the salesman, his manager or the dealer principal can't give you straight answers on this stuff and back it up by showing you the paperwork go somewhere else where the staff have had proper training.

What are the DPF exclusions ? The VW group for example I understand have a clause that gives them an out for driving patterns that are not condusive to healthy DPF operation...but do their salesman warn customers about this, or are they more fixated on their next commission cheque ?

When you look at the limitations of the DPF's the latent potential problems contained therein, the cost and inconvienience of potential trips with no other purpose than to clean out the DPF, future maintenance costs of the high pressure fuel system, expensive Pzizo injectors, general extra maintenance for diesel's over petrol and extra up-front costs of diesel vehicles...how much do you really save with a diesel vehicle over the long run....food for thought. My advice learned from very harsh experience, Take a very healthy dose of cynacism and objectivity along when looking at diesel vehicles.

Last edited by Rodge; 22-09-2012 at 11:44 AM.
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