Mercedes DPF Goodwill - any experience?

[18FAN]

I've had my C250cdi coupe for just under 2 years from new, it's covered 30k and so far it's broken down 4 times in the last 6 months!!

The first time was the coolant housing which developed a leak. It was fixed under warranty but then needed to be fixed again 2 weeks later for the same fault!

A month ago the DPF filter apparently got clogged up - apparently as I cover circa 120miles a day so it should be getting hot enough to burn off all the built up soot. Quite a scary experience as the car went into limp mode and lost all power in the outside lane of the motorway.

Last week the same happened again. The car has been with Mercedes since last Sunday (22/9) and is still with them. So now it's 10 days and counting. When I chased the service manager on Friday he said that they had replaced all the Z injectors and then had to take it on 4 test drives each lasting 1h 15mins to trigger the DPF regeneration. On this final test drive the car apparently broke down again so they replaced the DPF sensor and the techy will be taking the vehicle home so that he can perform the 4 test drives again over the weekend to ensure the car is fixed. I was expecting the car to be ready yesterday but I haven't heard any news from them today and the service manager hasn't returned my call.

I'm getting to the end of my tether with this car now and Mercedes don't seem to know what they're doing! Am I being unreasonable in thinking this is an excessively long time for the garage to have the car? Let alone how long these test drives are?

Has anyone else experienced this level of customer service/ or issue with their car? And if so did you have any luck in getting some goodwill from Mercedes?

Thanks in advance.

[cobra kid]

The techy taking it home.....

[Crusoe]

I'd want to check it wasn't in the body shop getting something fixed. If it isn't too far out of your way I would drop in and take a look at the car in the garage. assume you noted down the mileage it went in with.

[mrmr96]

I think you're jumping the gun a bit here. It doesn't sound like they've done anything wrong or out of the ordinary to be honest.

[Crusoe]

MERCEDES advice in the handbook is that that any DPF car should undertake a journey that lasts for at least 20 minutes every 500 kilometers [ 300 miles ] to allow the regeneration process to take place.

20 min in a low gear should easily be enough to get the exhaust system hot enough to regenerate though you might not be driving fast enough in higher gears on your commute to trigger it. Taking your car on at least nine hours of test drives sounds like a piss take to me.

[mrmr96]

Crusoe said:

MERCEDES advice in the handbook is that that any DPF car should undertake a journey that lasts for at least 20 minutes every 500 kilometers (300 miles) to allow the regeneration process to take place.

20 min in a low gear should easily be enough to get the exhaust system hot enough to regenerate though you might not be driving fast enough in higher gears on your commute to trigger it. Taking your car on at least nine hours of test drives sounds like a piss take to me.

But if, during their testing, they can't replicate the issue? What then? Return a car to a customer without a satisfactory resolution? I'm sure he'd be more annoying getting an un-repaired car back?

I doubt that they're paying their staff and paying for fuel to drive around for fun.

(Edit to fix formatting.)

Edited by mrmr96 on Tuesday 1st October 13:07

[Crusoe]

OP said:

techy will be taking the vehicle home so that he can perform the 4 test drives again over the weekend to ensure the car is fixed.

I read that as one of the mechanics is going for a long weekend away and taking his car, or there is more to it and they are stalling the OP while they fix something they don't want him to know about [from they haven't got round to even looking at it yet, to they crashed it and are waiting on the new parts being painted].

Would expect at least 500 miles to have been added to the mileage if they have really done eight 75min regeneration road tests. If I was the OP I would rather drive those miles myself to see if they had fixed it.

I would have expected them to replace the clogged up DPF first or cleared it out if that was really the issue, rather than replacing all the injectors and then the dpf sensor. But if they have replaced all that I wouldn't expect there to be an issue needing another set of 5hr drives.

[Paul O]

Another way to look at it is that they think they have now found the fault through extensive testing, but they need to continue extended drives to ensure the problem has been absolutely resolved - in effect mirroring your daily commute (they don't want it to fail you again in the outside lane). Its a busy workshop and the repair time is quite extensive, but their technician has oferred to work 3 hours overtime this weekend to drive the car about and confirm that all is now well.

I don't think they are doing anything bad to be honest. They are trying to fix the problem and have been honest about what they intend to do.

If they have given you a courtesy car, I wouldn't worry. You are going to be clocking up more miles on their car than they are on yours.

[mrmr96]

Crusoe said:

I would have expected them to replace the clogged up DPF first or cleared it out if that was really the issue, rather than replacing all the injectors and then the dpf sensor. But if they have replaced all that I wouldn't expect there to be an issue needing another set of 5hr drives.

But with respect, you don't know what was wrong with the car. You've not seen it, or plugged stuff into it, or tested it. You've only got the OP's side of the story, and even he won't have access to all the things that Merc will have looked at or tested.

I'd expect that there is a defined testing procedure when a car is presented with a given set of symptoms. This procedure will have been designed by Merc in Germany and it will be what the garage is following. It may be that clogged injectors can make a car appear to have a DPF problem, and it may be quicker and cheaper to try that first, so it will be in the procedure first. If that doesn't work (after extended drive to test) then they can look at the next thing in the flow diagram.

You could argue that they should replace the DPF, Injectors, Exhaust, Intake Manifold, Engine, Gearbox, and Car, just to be sure it fixes it issue. But in reality they'll be following a sensible and logical procedure with it.

PS - It does make sense to try inexpensive fixes first, even on cars under warranty, because ultimately the cost is passed on to Merc customers eventually.

[mrmr96]

Paul O said:

Another way to look at it is that they think they have now found the fault through extensive testing, but they need to continue extended drives to ensure the problem has been absolutely resolved - in effect mirroring your daily commute (they don't want it to fail you again in the outside lane). Its a busy workshop and the repair time is quite extensive, but their technician has oferred to work 3 hours overtime this weekend to drive the car about and confirm that all is now well.

I don't think they are doing anything bad to be honest. They are trying to fix the problem and have been honest about what they intend to do.

If they have given you a courtesy car, I wouldn't worry. You are going to be clocking up more miles on their car than they are on yours.

+1 to this too.

[18FAN]

I opted not to take a courtesy car as when I did so the last time they were fixing the dpf fault they called me at 4pm stating they had fixed my car and that I needed to return to their workshop by 5.30 with their car so that they could swap the cars over otherwise they would charge me for additional hire of their vehicle.

When I told them I can't just leave work immediately and even if I could I probably wouldn't be able to cover the journey before they closed they told me to take it up with head office.

I didn't want to deal with their threats again so thought I was best out of it!

The other issue is that the car is leased at 10ppm excess charge so if they're covering 500miles for example that is a real cost I'm incurring.

From my point of view I think 10 days is an excessive amount of time for a franchised dealer to take to fix the fault.

[Engineer1]

The point is they are trying to fix the car which sounds like it has intermittent problems, would you as the owner prefer they chuck it back to you saying NFI what's wrong keep an eye out incase it does it again, all the time watching the warranty clock run down and feeling uneasy about the car's reliability. Or they keep it a reasonable period of time do all the tests they can to get to the bottom of the problem hopefully leading to the OP getting his car back with some extra miles on it but the knowledge the fault has been identified and resolved.

One of these leaves a Normal owner looking to get something less unreilable (and probably a different Marque) the other leaves the owner slightly inconvienced but happy in the end and more likely to remain loyal, looking at a new Merc as their next car and only looking else where if Merc haven't got a car that suits.

[mwstewart]

mrmr96 said:

I'd expect that there is a defined testing procedure when a car is presented with a given set of symptoms. This procedure will have been designed by Merc in Germany and it will be what the garage is following. It may be that clogged injectors can make a car appear to have a DPF problem, and it may be quicker and cheaper to try that first, so it will be in the procedure first. If that doesn't work (after extended drive to test) then they can look at the next thing in the flow diagram.

A prescribed procedure that sees all their technicians out for nine hour drives? DPF failure isn't uncommon and must surely figure highly in 'risk of occurrence' calculations, therefore I would expect the procedure is to replace the DPF if no other DTCs are logged.

This is surely cheaper than loosing a mechanic for nearly 1.5 days.

[mrmr96]

mwstewart said:

mrmr96 said:

I'd expect that there is a defined testing procedure when a car is presented with a given set of symptoms. This procedure will have been designed by Merc in Germany and it will be what the garage is following. It may be that clogged injectors can make a car appear to have a DPF problem, and it may be quicker and cheaper to try that first, so it will be in the procedure first. If that doesn't work (after extended drive to test) then they can look at the next thing in the flow diagram.

A prescribed procedure that sees all their technicians out for nine hour drives? DPF failure isn't common and must surely figure highly in 'risk of occurrence' calculations, therefore I would expect the procedure is to replace the DPF if no other DTCs are logged.

This is surely cheaper than loosing a mechanic for nearly 1.5 days.

Like I said, none of us here know what the testing so far has shown.

You'll also see in an earlier post that I don't think they're sending their drivers out in the car incurring time cost and fuel costs for the fun of it. It's in their best interests to get the car mended and returned to the customer.

[Crusoe]

The diagnostic computer should be able to show if the pipe is blocked or not and if the car is trying to run the regeneration cycle. On a c class they can manually trigger the regeneration in the garage to force it to regenerate when they want so they should already have tested that the pipe is clear and that the regeneration system works without doing any mileage.

Assuming it did clear when they ran the diagnostic and it did regenerate when prompted then the dpf should have been clear. If the diagnostic also showed some over fueling or incorrect running (needs to inject more fuel to build up the temperatures for a dpf regeneration) then I could understand the injectors being replaced next and then the dpf sensor to top it all off if it wasn't sending the signal back to get it to regenerate.

I don't see any reason for 10hrs or road tests though. Possible that low soot oil wasn’t used the last oil change and would explain why the OP's commute might not be able to clear it but if OP was getting good MPG then it is likely everything was fine except the sensor or the computer that should interpret it.

[mrmr96]

Crusoe said:

I don't see any reason...

You've not seen the car either. If you want to argue what-ifs then that's your prerogative, but I don't see how it helps the OP to go speculating. At this point in time, having only had the limited info from the OP, I don't think there's currently a cause for concern that the garage is acting in bad faith. I'm trying to reassure the guy that there's nothing to be worries about yet, but some people seem to want to make a big deal of things.

[18FAN]

mrmr96 said:

You've not seen the car either. If you want to argue what-ifs then that's your prerogative, but I don't see how it helps the OP to go speculating. At this point in time, having only had the limited info from the OP, I don't think there's currently a cause for concern that the garage is acting in bad faith. I'm trying to reassure the guy that there's nothing to be worries about yet, but some people seem to want to make a big deal of things.

I appreciate your comments on this post but I think part of my point with it was that I don't see why the garage have to take the vehicle on such extensive test drives. A DPF regeneration can be done manually in the garage and so far it has been serviced with Mercedes dealerships only so there shouldn't be any issues over the oil used.

By Friday last week they had completed a DPF regen, replaced the Z injectors and replaced the DPF sensor. Having just spoken to the garage now they are saying the vehicle is still not yet ready. It all sounds slightly vague and doesn't inspire confidence.

I'd have thought that a competent franchised dealership would have resolved the issue after having had the vehicle for 10 days.

I think the dealer have had enough time to fix the fault with the car and and my preference would be to chop the car in, however, I'm aware it is unlikely to happen and would be a lengthy process. To confuse matters further when I spoke to Mercedes head office on Monday last week they asked if I would consider exchanging the vehicle with another which I thought was odd at the time. However when I spoke to them on Friday they said they would not consider it on a car over a year old.

Edited by 18FAN on Tuesday 1st October 14:49

[surveyor]

I do, just occasionally feel sorry for dealers. They really can't win.

OP it sounds like they are dealing with a difficult to diagnose fault, and are working on it.

As for the staff taking it home, I'm sure that if the OP did not want them to they would honour his request, but he'd then have to be the guinea pig. I've had them use my car in the past when it's being awkward with cold faults, or things that reappear. It's the garage doing the job properly, which those used to ford and Renault dealers will be suspicious of

[panholio]

It does sound suss. But maybe they are genuinely trying to sort the fault.

Have a wander down there, see if you can see your car to get any thoughts that they have damaged it in some way out of your mind - I'd be asking for a courtesy car with no daily charge at least. My local Merc dealer doesn't charge for them.

[mrmr96]

18FAN said:

I don't see why the garage have to take the vehicle on such extensive test drives.

As several others have said - would you prefer they just gave the car back without finishing the work? Probably not. Why is the work taking longer than you expect? I don't know. Have you asked them? If not, I'd probably start there rather than working yourself up into a lather over it.

I think some of the totally OTT reactions on PH are responsible for setting some pretty unrealistic expectations. You have a 2 y/o car which has been with the dealer for what, 10 days? And you want to get rid of the car now?

Ok, I can't reason with the unreasonable. It's not possible. Good luck, hope you get a decent resolution to this all.