Hi, This is my first diesel and also my first Mercedes. I'm loving the car and since I have had many years wrenching I believe I can take the challange.

I am having an issue with #2 injector and I'm clueless to what I need to do. Engine runs fine has plenty of power and doesn't seem to be missing.
However, I have some soot blowing up from a half-moon shaped hole at the base of the injector. All injectors have this same half-moon shaped hole at the 4:30 oclock position looking from the front of the engine and none of the other injectors are puking soot but this one. I am also hearing a significant tapping sound from this location and I think this sound is sometimes referred to as "nailing". I only can really hear it at idle.

My question is what is the problem. Is there a seal that's gone bad and if it is what is it called. I bought some injector seals from the dealer but I don't think these are the culprit as they are too small diameter to be causing the soot I am seeing unless I am just clueless. I don't know how to remove the injector as there are flats on both sides of it near the top but there is a much bigger hex near the bottom of the injector. then it looks like there is another type of insert below that that appears to screw into the head and this is also where the half-moon hole is just at the outside diameter of the insert looking thing.

Can someone please explain?

Steve

I have heard some references to heat shields for the injectors. I this what the lower insert thing is for? I'm only guessing here so please help me out.

Steve

The problems you have might not be worth fixing. Have you heard other 603 engines? A clack sound is normal. If nailing, swap injectors from different cylinders and see if the sound moves.
The head opening for the injector has a few pieces. Pre chamber seal rings (shims) go into the head, then the pre chamber drops in. A hold down collar (bushing) is screwed in. Then the heat shield is installed followed by the injector which is screwed into the collar.
Is the soot actively coming out or just staining the area? If the pre chamber seal rings are leaking, I do not know if they can be replaced with the head on the engine since the pre chambers may have to be pressed out because of carbon deposits. The repair manual describes how to refinish the head where the pre chamber seal rings sit, to fix a leak. It looks like a job for a professional mechanic.
Injector removal requires a 27mm deep socket (Sears works), return lines and heat shields. If you wish to remove and refit the collar and the correct tool is not availaable, a heavy angle bracket can be used as a wrench.

Hey thanks for that info. Yes the soot is actively leaking from what I think is the pre-chamber seal. I have ordered a shop manual that should arrive next week and I'll check things out then when I can look at the pretty pictures. I hope I can fix it without removing the head.
Steve