PeachParts Mercedes-Benz Forum - View Single Post - injector heat shields for a 300D

JimSmith · #13 08-20-2002, 02:18 AM

Robert,

Sorry I was off line for a week on a trip. Just got back today and started looking at some of the threads to check progress.

The old seals sit in the bottom of the prechamber, and are a different color (darker) than the prechamber. They are nothing like the new ones that look more like a shaped quarter or something of that size. The originals were shaped like a top hat (that was open across the top of the top hat), and put into the prechamber with the top of the hat down, into the hole in the center of the prechamber. The "rim" of the top hat was pretty small, and the outside diameter of the rim was less than half that of the new shields. This is all from memory as the manual is useless in this area. It just says take the old ones out and put new ones in. The drawing of the engine cross section shows the old ones though, and they bear on the injector nozzle face, in fact they are the same outside diameter as the nozzle of the injector to give you an idea of how much smaller they are than the new ones. They are called "nozzle plates" in the manual, not seals.

So, if you have both in there I would expect your injectors are sticking out higher than they should, and if you are not leaking by it is luck. The injector seals to the prechamber just below the threaded section of the injector, I believe, and that injector body shoulder will not bear down on the mating surface if there is something holding it up underneath. So you are sealing on the nozzle plates, not the design location.

I hope this is not more confusing than it was before I decided to clarify the situation. If I had no trouble, and the injectors seemed sealed, I might wait until a day when I was really bored, and then I would take one out to look. If it had two pieces in there I would take them all out and put new, unused ones of the later design back in, and call it a day. Good luck, Jim