Mysterious diesel leak S210 320cdi

[js190d]

I have spent the best part of Sunday afternoon painting the inner front wheel arches on my s210 320cdi. Jacking up one side, painting and then doing the other side as well. All nicely sealed off now to hopefully keep the rust at bay for the coming winter.
This morning i start the car as usual, starts on first turn of the key after not being started since Saturday and as i pull on to the road i notice it is leaking diesel.
Pull the engine covers off and there is no diesel leak from anywhere on the top end, everything dry as a bone. Following the fuel lines from the fuel filter all bone dry. Jack the car up and the drips are coming from somewhere near the sump plug.
Drive the car around for 10 minutes everything as normal drives fine and now there is no leak.
Does anyone have any idea what could be (temporarily) leaking diesel from the sump plug area.
Also could not see where the diesel injection pump is, as my first thoughts were delivery seals leaking on the pump as i have had this problem on my 190d.
Any thoughts anyone?

 

[mersum1es]

https://avtochast.ru/images/MB/3/39ff130b504aa82d885618d915d077d9.gif

hp pump is that 3 piston star shape block, often starts leaking under one of the pump cylinder head. In the beginning leak is worst at cold and may stop when warm. Take of plastic cover, then start the engine and see if it is dripping fuel on serpentine belt or on the fron of the engine.

 

[js190d]

Thanks for the reply mersum1es. Serpentine belt is dry, no diesel leak in that area. Is the injection pump (OM613) at the front of the engine directly above the fan?

 

[mersum1es]

Thanks for the reply mersum1es. Serpentine belt is dry, no diesel leak in that area. Is the injection pump (OM613) at the front of the engine directly above the fan?

Yeah, here white label on it (picture is from 4 cyl engine, plenty of space there lol):
https://mbworld.org/forums/attachments/c-class-w203/252013d1358962593-tank-fuel-pump-img_3239-1.jpg

aux (transfer pump) is above it, cigarette box sized block

 

[js190d]

Thanks again, now at least i know where the pump is! It does look dry in that area, and i can't work out how diesel would get from there to sump plug area.

 

[alexanderfoti]

Have you taken the engine covers off and checked its not from the leak off hoses? They will fill up the injector channels and then run down a drain in the back of the head.

 

[js190d]

Thanks for the info Alexander, i will check if this might be the cause when i start the car tomorrow. Do the leak off hoses on an om613 drain diesel externally? I always thought they would return diesel to the fuel tank. When i took the covers off this morning the area around the injectors was dry.

 

[om613]

If it's not the leak offs nor the IP areas leaking, then focus on the fuel filter and push fit pipes (and they're above the sump plug...)

 

[js190d]

Thanks om613 advice much appreciated.

 

[alexanderfoti]

Thanks for the info Alexander, i will check if this might be the cause when i start the car tomorrow. Do the leak off hoses on an om613 drain diesel externally? I always thought they would return diesel to the fuel tank. When i took the covers off this morning the area around the injectors was dry.

No, they T into the return to the tank. If its dry under the covers then its not likely to be that, but do check.

 

[js190d]

Well just started the car and it is leaking from the bottom left hand corner of the pump straight onto the serpentine belt. I restarted engine after running it from cold for a couple of minutes and no leak. I guess a seal or two has gone. Must have dried off by the time the engine was warm and i had the covers off yesterday.
Is this job easy enough to do as access is pretty tight? I have done the seals on my 190d 2.5's pump and that was easy enough but access to the injection pump on that engine was good. I also have no idea about this common rail diesel witchcraft.

 

[Taffy7hfa]

First of the cold weather diesel leak questions ! if it only leaks when the engine is cold and temps are low its probably the pump.

 

[Blobcat]

First of the cold weather diesel leak questions ! if it only leaks when the engine is cold and temps are low its probably the pump.

Wet footwell from leaves blocking the water drains next

 

[om613]

I'd start with changing the two clear pipe o rings, as they leak much more frequently than the HP pumps.
I could post you some for next to nowt.

 

[js190d]

Thanks om613 that's a very kind offer (i don't suppose you have the part numbers for these o rings). It's a bit warmer today and no leak! Are the clear pipes hidden under black flexible hose covers (one on each side of the pump)?
Do you think it is possible to change them without removing the pump if i remove fan shroud, aux belt , intake pipes etc.

 

[Taffy7hfa]

The fact that it only leaks when outside temps are low indicates that its the HP pump not the O rings.
if it was the O rings it would leak regardless of the temperature.