[jrobbins70]

The service schedule for my r350 bluetech says change the diesel fuel filter every 20k miles. I admit that I accidentally missed changing it when it was due at 20k miles and saw no ill effects. I replaced it at 40k miles but am now coming up on 60k miles.

If I skipped it again, what's the risk?

 

[ptbowman]

It's difficult to say... diesel fuel is inherently dirtier than gasoline and its quality can vary widely. You can get lucky and go for 40,000-50,000 miles with no ill effect or you can get a few tankfuls of dirty fuel and plug your filter up. Also, if there is any water in the fuel, algae will grow turning the fuel in your system blue; the filter takes that out.

Bottom line -- you can get away with intervals in the 20K-30k range (I have done that myself), but you are incurring increasing risk beyond that. What's the worst case scenario? The filter plugs, your car stops running, and then it's "flat bed time"; by the way, I have often found even the dealer doesn't have the filter in stock, so they have to special order it with a 1-2 day wait.

If you're mechanically handy at all, replace the filter yourself; it's only $45 (at the dealer) and you save ~$150 in labor. I can do mine in about 30 minutes and it's readily accessible during an oil filter change.

 

[starbound01]

The there IS the fuel pump risk. There are countless threads on the failure of consumers to replace fuel filters and their increased risk to fuel pump failure. Deadheading a pump is a sure fire way to make it fail. You have to judge for yourself if the $40 filter (which you would have to replace if the pump fails) is worth the $300 + labor cost of replacing the pump.

If it were me, I'd learn to replace the filter and replace the filter.

There vehicles are fairly intimidating to work on because of the vehicle value and the risk of doing something wrong/breaking something. But basic maintenance is very easy and requires not much more time than any other vehicle.

 

[jrobbins70]

Thanks for all of the great advice.

I do alot of my own servicing myself like air/cabin filters, oil change etc. But the fuel filter is a really nasty job with a potential to spill diesel. That's why I prefer the stealership do the job.

It just seems odd that the fuel filter is due every 20k miles and is expensive versus a gasser engine. I guess it just comes with the increased cost of running a diesel engine.

 

[ptbowman]

Thanks to "starbound01" on the potential for a plugged filter killing a pump -- I forgot about that. Some owners have even claimed that a partially plugged filter will shorten pump life -- it doesn't need to be completely plugged to have an adverse effect.

As I mentioned, diesel fuel is dirtier, hence the more frequent replacements. You can get an aftermarket filter for half the price of the dealer filter, but it doesn't come with the the o-rings that the OEM filter comes with. I learned the hard way to always replace the o-rings. You can also buy the aftermarket filter and o-rings separately... which I may try the next time around.

Not sure what you mean by a "really nasty job" -- I actually prefer diesel filter replacement to replacing a gasoline filter for 2 reasons: (1) I don't have to worry about the explosion risk of dealing with gasoline vapors, and (2) my "gassers" have fuel filters under the car which means you can get gasoline running down your arm as you loosen the hose clamps and you need to quickly clamp on the hoses once they are loosened so fuel doesn't spill everywhere. Also, in the typical undercar environment the gasoline fuel filter is often encrusted in rust, salt, dirt... a real messy job. With Mercedes mounting their diesel filters up in the engine compartment "above it all", the filter is much easier to get at, not encrusted in road debris and I don't have to worry about fuel potentially spilling every where.

 

[efzauner]

Its not hard to replace. I do it every 2nd oil change.
I suggest you get a quick clip remover on ebay
search:
Universal/Mercedes/BMW/Audi/VW Collar Hose Clamp Pliers Clic and Clic-R Type

and get a few spare clamps from the dealer.
you will have to remove the air intake to the turbo.

 

[2008R320]

Its not hard to replace. I do it every 2nd oil change.
I suggest you get a quick clip remover on ebay
search:
Universal/Mercedes/BMW/Audi/VW Collar Hose Clamp Pliers Clic and Clic-R Type

and get a few spare clamps from the dealer.
you will have to remove the air intake to the turbo.

Agreed, I'll do my fuel filter this time my self, thanks for the link.

Also replace the orange turbo inlet seal, it cheap but leaks over time with the heat, I can't of my head now remember the part number and price.

 

[ptbowman]

In case you haven't seen this:

http://www.benzworld.org/forums/w251-r-class/1622137-cdi-fuel-air-filter-diy.html

 

[2008R320]

In case you haven't seen this:

http://www.benzworld.org/forums/w251-r-class/1622137-cdi-fuel-air-filter-diy.html

Thanks already printed it and will attempt the repair, service is only 1500 miles away now.
But as I have replaced the brakes and other parts on the engine I'm sure by following this it will be easy.

I'll also do the following on top of the normal service;

- Replace power steering fluid
- Replace brake fluid

Planning to run it close to 10 years if possible as we love the car

 

[ptbowman]

Great! Ours is over 7 yrs old and will pass 100k miles in a few months. Still running strong! The interior is still relatively tight although it does have a few minor rattles that occasionally pop up.