Any clues to my OM606 diesel leak?
 

Hi!

My W124 OM606.910 (NA) is leaking diesel quite heavily. Since I can run it just fine, I guess it has to be one of the return hoses (right?).

Before I order new plastic fuel lines and pull the intake manifold (scary), can you tell from my video where the leak is coming from? Like, is it 'obviously' from a known trouble area? https://www.youtube.com/watch?v=AGlhLjBwHzo

Will there be issues with air in the fuel system after replacing them all? Any precautions there?

Any help is greatly appreciated!

uhhm.
I don't know where to start. It truly looks as if you are attempting to irrigate every road you drive on with diesel. I have never seen a diesel sprinkler before. wow.

I don't think I would classify this as a "leak". . . its a full blown geyser.

Start by replacing all the o-rings on the entire fuel system. Theres one at each end of a hose and basically one at every interface between plastic parts and plastic to metal contact on the fuel system.

A healthy system will not have visible air bubbles in the lines. Do you see how much air you have in that line in the video? - - i think theres more air than fuel. How you can say it runs fine is beyond me.

The delivery valve orings on the top of the injection pump look like they might be the source of the leak. But it could just be dripping down from the fuel heater above.

I would do those at the same time as the fuel system orings when you have the manifold off.

Thank you for input. I meant to say (not my native language, sorry if it sounded as if I didn't take the issue seriously) that it simply runs, even though it leaks that heavily.

I guess the air in the return hoses will end up back in the tank and bled somehow (and less catastrophic than air in feed lines?)?

I figure I will replace every single o-ring and plastic fuel line while at it, and doing the delivery valve seals too. The grocery list below got rather long...

I've never removed an intake manifold before, and also it kinda worries me that I will get so much air in the system the thing won't start afterwards, and the OM606 doesn't have a hand primer pump AFAIK...:confused:

0049974540 6 Delivery Valve Washer
00760302113 2 Banjo bolt seal ring
0179974148 6 Diesel delivery valve seal
6010705332 1 Fuel line - fuel filter to IP
6010780486 7 Nozzle holder
6010782641 7 Fuel Line Bracket
6010900352 1 Main screw-on fuel filter
601092105 1 Pre filter
6019900863 1 Banjo bolt
6019970148 1 Pre filter seal ring
6030780141 7 Fuel Line Bracket
6049970045 2 Intake manifold seal ring
6050701432 1 Fuel line with fittings - fuel heater to prefilter
6060160081 6 rubber corner breather bung
6060160181 6 rubber straight breather bung
6060700032 1 Fuel line with fittings - feed pump to fuel filter
6060700232 1 Fuel line with fittings - prefilter to feed pump
6060700532 1 Fuel line with fittings - injection pump to fuel filter
6061410080 1 Intake manifold gasket
6069970645 2 Intake manifold seal ring - intake line to EGR valve/mixing chamber
617589010900 1 Special tool

I wouldn't do all of them at once.

Make sure your engine is nice and warm before you start as it will make it easier to get started again.

I always do one at a time and then start engine, stop and do the next one and so on.

Give that injection pump a good clean up before you do the delivery valve seals.

Good to see in your 'parts required' list that you have included the high pressure line plastic clips as they are pretty important-mine almost rubbed a hole in two of the lines due to rubbing.

I din't see any return hose for the injector return lines on your shopping list. Best to use the grey line with the orange stripe (3.2 x 7.0mm) size from Mercedes or OEM (contitech I think). I've tried all others even other German made stuff but they all leak in no time.

Were you working on or near something for the leak to suddenly appeared like that? How many miles/kms on the engine?

Thanks a bunch for the reply! I first noticed a large stain on the ground when I was headed home from work, it began spontaneous. The car has 170.000 km on it.

If I am to run it in between replacing each part, I assume it's not dangerous to run it without intake manifold? Will it unleash hell sound-wise? I ask cause I share garage with lots of neighbours :)

My shopping cart consists of the parts mentioned in PeachParts guide, as well as a guide of a member of a UK MB forum. Neither mentioned the return fuel hose, great find! I ordered it just now from my swedish MB dealer. With my G-wagen om617, you can clearly see all parts and plan ahead. But this is all unknown territory for me, as I have yet to remove the intake manifold. I just ordered what the guides say...

Again, thanks!

FIRST... you need to address the air in the fuel line!

that leak is NOT the first problem. the LARGE clear hose feeding the IP should NOT have any air in it.

take another video but move the camera along the top of the IP, and on up to the first spot where fuel is pooling.

My guess is the fuel line to the fuel tank is corroded, and drawing in air. try removing the fuel filler cap to see if maybe your tank is under a vacuum. if that stops the bubbles in the line, move on to the leak.

from this video, it's hard to say if the fuel is coming from the Delivery Valves or someplace above. it could easily be return hoses just spraying under the intake...

pull it off, and the injector cover off, and look for the highest source of fuel spray.

i've NEVER seen DV seals leak that badly... and I've NEVER seen a car with leaking DV seals start up easily... without needing to bleed the injector lines.

Removing the intake manifold is not too bad. All the star bolts on the top, one hex bolt from underneath the car, and one clamp that holds the EGR on under the IM.

I don't remember off the top of my head the sizes of the bolts.

The one from the bottom can be a little tricky. Remove the small black plastic cover under the car (the one you would if doing an oil change). Look up toward the bottom of the IM and you will see a hex bolt on a bracket. Take that off. You will need extensions and a universal to grab hold of the bolt. (I use a wobble extension and a universal on a 1/4" drive). I believe the bolt is a 10mm but don't quote me on that.

The clamp holding on the IM to the EGR, you get from the top. No need to remove the washer fluid tank. Again I think it's a 10mm. You have to get your hands under the IM a bit. Loosen the bolt that tightens the clamp and be careful not to drop it. Once the bolt is off, open up the clamp and slide it over the tube or remove it altogether and set aside with the bolt (so you don't lose it)

The star bolts on top are self explanatory.

Now just lift off IM.

The fuel tank is indeed under a vacuum - shouldn't it be? Removing the fuel filler cap had no effect on the bubbles - why should it? Thanks for clarification!

mmm, noise is not very socially acceptable if you are in a shared garage.

It is possible to replace 4 of 5 plastic lines without removing the inlet manifold, just need to remove cross-over pipe. Banjo bolt is a bit tricky but doable (see pic) So, you could do those first then get it started and then move onto the rest. That leaves one more plastic line to do and the delivery valve seals when you get the inlet manifold removed.

Regarding the leak. Have you removed the cross-over pipe and black plastic engine cover to see if a return hose has perished or coming off one of the injectors?

At 170,000km it is still a baby! That said, rubber is rubber and will deteriorate from age.

A full tank of diesel will help with the starting/priming.

In your video I also noticed the "emergency" shut off valve located on top of the main fuel filter has its plastic knob removed. Those things are notorious for leaking and very difficult to service as well as being a very expensive bolt!

If at least for the short term (and testing purposes) you might want to simply replace it with a bolt from the later W210‘s. You won't have an alternate shut off like in the OM603‘s but there is modification you can do as contributed by Jeremy4858 on this forum. He has been very kind over the years sending me parts not available to our market which included the said bolt.

The tank is supposed to be vented. It may be under a slight vacuum before it vents... but very slight.
If the tank was under severe vacuum, leaking lines could heavily suck bubbles.

Alright, thanks for the further insight everyone! I should be getting all parts later this week, and get to it on friday. There seems to be so many causes for error. I'll just replace all seals and hoses and see what happens. Hopefully I don't run into too much trouble.

If it was me I would replace the hoses first and make sure the engine starts before messing with the DV seals. Even if you have to go on/off with the IM twice, it's not that hard to remove once you know the tricks.

"Break only one thing at a time" is my rule of thumb, I am a field engineer that deals with power systems and this applies here too.

When you get to the DV seals, be sure you have an accurate torque wrench, keep things surgically clean, and follow the process exactly. Otherwise you will have a very expensive paperweight. Go on YouTube and look for dieselmeken for a video that shows the exact process.

Found it:http://youtu.be/-SW1dRGpHPU

In that video he shows removing the shut off valve. You don't have that, they started using that in 1996. But the process for the DV seals is exactly the same.