190DT Injector Seat Leak

My 190DT nails, so I bought Monark injectors from Mercedes Source and all the gear to clean and balance the injectors. As I was testing the motor after putting the injectors back in I noticed some bubbling from under the plastic injector shroud. I pulling injector and put it back in without the shroud so I could see what was going on. The bubbling looks like it is coming from the interface between the threaded ring and the head. Also, the injector hole seams to be more oily that the other holes and the exposed face of the injector was black after just a couple minutes idling. Thoughts?>

Forums

Diesel Engine Specific Aid

Chassis Model Number

W201

Tool coming soon

Check out one of my newest videos that will explain how to fix the problem... CLICK HERE.

Thanks! Great video.

Update

I got the splined socket, pulled the threaded ring out and re-tightened. It looks like one leak was fixed and the #3 cylinder lead was not. The manual doesn't show a sealing ring and I read someone else saying that the 602 is metal on metal and that cleaning the carbon deposit worked for them. What do you think?

Since the injectors did not fix the loud nailing sound at idle could it be the injection timing? To me it sound like the engine proper and not the engine shock or vaccum pump or other external issue.