MB Diesel Reliability - Fact or Fantasy?

[Marco Polo]

I've been thinking that my next car would be a 2004 or later W211 E320CDI estate (to avoid the rust issues that I have on my W210 E240) .

I have not had a diesel before - the main attraction being economy with good performance, and perceived reliability and longevity.

I must admit to a certain reluctance to turn my back on a petrol engine - my only previous diesel being a Vauxhall Omega 2.5 Diesel 1996 vintage which was awful in terms of clatter and power delivery. But each time I go to Germany, I see all those E Class taxis at the airports and train stations.

But then on the BMW forum that I use, there are on-going horror stories relating mainly but not exclusively to 320D's that are costing £thousands to put right since BM do not aknowledge that there is a major problem. This also seems to have affected 525 and 535's to a lesser extent.

I know that the MB 320CDI has changed from a straight six to a V6 - has this affected reliability, and is the reliability fact or fantasy? Having done a search, most diesel problems seem to relate to the MAF (whatever that is/does?) but not ones that result in terminal failure.

What are your experiences and views on this?

 

[jberks]

Hard question.
I would say that a diesel is capable of handling many more miles than a petrol engine. A petrol engine will start to show its age by 150k or so and need major attention by 200k whereas the same level of wear on a diesel will not come until probably 250k+ and not be looking at serious work for another 75-100k on top. I'm sure there are engines out there with 500k on them that have never had the head off. It makes sense really. Diesels produce their power lower down and red line at 4500rpm. The same level where a petrol engine is gettting into its stride so if an engine has a number of cycles in it, the diesel will take longer to clock them up.

However, in terms of reliability, it's a different story. Diesels need injectors, glow plugs and can have turbo issues well before such issues would affect petrol engines. So swings and roundabouts really. If you plan on doing very big miles, then yes a diesel is your best bet. If not, then there is not as much in it as you might think. MAFs affect petrol and diesels equally so not really a factor (Its the Mass Airflow Sensor that measures airflow into the engine). They are the most common failure on any modern engine and cost anything between £60 and £300.

Compared to your Vauxhall, yes the 320cdi is a revelation. There have been 3 eras in diesles really. The old smokey underpowered ones of the 80s and early 90s, the CDIs of the late 90's early 00s which were powerful, still sounded like diesels and had short power bands (hit it right and it will play with a Porsche, wrong and a metro will outrun you!) , and the new breed that have a similar power delivery, sound and refinement to petrol engines, only return 40mpg.
Don't take out a V6 320cdi unless you can afford one as it spoils you for anything esle!

Coming from an E240 (like you), the diesel feels harsh and noisy but you acclimateise quite quickly and it's compensated for by the power and economy. To be fair, the 320cdi isn't that much more economical than the 240 (I got 3-5mpg more on the motorway when I had one) but in terms of performance it's in a different league. No more kicking down to pass something on the M1 and once up to speed whilst not as quiet as the 240, it is still quiet and relaxed.

There is a post by another member regarding costs of a 320cdi estate over 100k or so. Well worth a read.

 

[Blobcat]

I was that other member with the IL6 W210 E320CDI Link a glorious engine and car. I now have the V6 E320CDI and another glorious engine. I've covered ~16K miles in it since May and have had nothing to report. It is that good.

 

[Marco Polo]

Thanks jbercs for the detailed response. I do find the E240 underpowered but then my previous was an E300TE-24 which was really responsive.

I've seen your W210 breakdown before, Blobcat, and I'm glad you find the W211 has a glorious engine - praise indeed! Thanks for the testimonial.

You've restored my confidence in MB diesels in view of the disasters elsewhere with BMW. However, my annual mileage will not be much more than 10-12,000 so maybe I will go for a bigger engined petrol instead if I get one with say 60K miles and keep it for 4 or 5 years.

 

[television]

Yes when you get into the generation that Blobcat has then nothing can beat them.

Went out in my friends new S class CDI 2 weeks back , that again is some else, superb