So a couple of days ago I decided to switch to my new Monark injector nozzles. I thought it might do my engine good since no one has done that in quite a while I could imagine. Changing the nozzles went fairly easy, but it raise quite a bunch of new questions and a rather big insecurity concerning the engine.

First of all, when I read the guides before, they told me it was important to change the heat shield to a brand new one every change. My father on the other hand said that if it was a copper washer (If that is the word) you could just heat it until it glows and it's plastic liken new. Anyhow, when I got the injectors away, there were no sign of a washer like this under any of the injectors.


Two of the injectors seemed to be original Bosch injectors (KCA30SD27/4) made in France (if that is even original?) and two of them were made in India (KCA30S44). To me intuitively these Indian injectors felt of less quality but I don't know if that's true at all, could be prejudices. What would you say about these? Would having two different kind of injectors pose a problem? I mean I have no way of testing that they both fire at 150 bar as they're supposed to but maybe that's the only importance?

Lastly the most important part that scares me the most. Under one of the injectors the metal was all worn down. All I could see was a thin layer of metal that I could scrape away with my screwdriver. I can imagine that fuel from the last injector nozzle did not get where it were supposed to and fired up too close to the metal. Now it seems to run equally on all cylinders, but this one surely doesn't look good. Do you have any opinions on this? I am currently looking for some old scrap car to use for spare parts and exchange the cylinder head.

So my questions summarized are:

• Should there always be a heat shield, this copper washer underneath every injector?
• The two different brands of injectors, is this an issue and should I also change injectors and not just the nozzle?
• The worn down metal in the cylinder head, how immediate of an issue would you say this is? I will drive about 1000 more km this year before the winter comes, then I rarely drive at all. Will I need to worry?

Beneath are three pictures, of a healthy whatever-they-are-called and the broken one. Also one of the two different kind of spreaders. Any ideas or help would be appreciated and especially if anyone has a good idea for a temporary quick fix for the cylinder head damage.

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The metal wear is actually carbon build up and the heat shield. The heat shield can be a pita to remove but they are in the bottom of each injector bore.

I removed mine by threading a 1/4" bolt into the hole and pulling them out with vice grips.

As far as the different injectors go, don't worry about it. You are replacing the business end of the injectors... Only thing that'll be left is a spring, spacer, and tapered spacer.

Pull each one apart (one at a time so you don't mix up shims and springs). Soak the parts in solvent... Wire brush and clean the parts... Lap the sealing surfaces on flat steel/glass with a piece of 2000+ grit paper... Reassemble with new nozzles.

You do want to replace the heat shields... They are 1.50 each from PelicanParts.

Reference...
Diesel Injector Cleaning DIY

-Chris

I don't see any problems at all with the pre-chambers, other than one has a heat shield and the other doesn't.

The heat shields are not easily identified by the inexperienced. Use a pick or something pointed and long and remove the heat shields.

It doesn't matter that you have different injector bodies, but you really should have them pop tested. Replacing the nozzles often changes the required sizes of the shims.

__________________
1981 300TD 310k miles
1970 280sel 172k miles
1966 230 Fintail 162k miles

"Where are we going? And why am I in this hand basket?"

Agreed.

The only suck part about pop testing/balancing these injectors is most shops charge about the same rate to rebuild them as they do to clean/poptest... at least around here they do.

May call around and see what your local injection shops would charge.

-Chris

Concerning you Dad's comment; a lot of Diesel Engines indeed use a Copper Crush Washer to seal the Injector in the Head but not your year and model of Mercedes.

My Volvo Diesel (made by VW) and VW Rabbit Engines from the 1980s also use Hieat Shields on the end of the Injectors.

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84 300D, 82 Volvo 244Gl Diesel

Ah, I see. Only one is missing a heat shield then. I will disassemble it again, clean out the carbon build up, order some new heat shields and fix that part. I see they're cheap here but I live in Sweden so I imagine it would be expensive shipping it here and also a bit rediculous shipping distance.

Thank you for your response! This seems to be one of the best places if you are into old Mercedes diesels

I am currently reading about reusable seals. Apparently they were common before and how would I identify these? Could it possibly be the ones in mine and is there any downside to reusing the ones I have now? What is the worst case scenario? Leaks?

I'd say if it wasnt stuck to the injector, then its in the bore and is just a different style. They make several different styles of heat shields and if it wasnt in place, it most likely wouldnt run to well.

-Chris

I lost you. How do you know they pop at that pressure? Do you just mean that is stamped on the housing? Whenever you change the internal nozzles, you need to pop test and play with the shims to get it right.

Where are you? There may be a member here nearby who has a pop tester and could help for a little money or parts trade. I made a nice pop tester, but don't consider it as important as others since I found 3 of 5 injectors in my 1984 popped at 1600 psig (non-turbo, as stamped on housing), yet changing all 5 to correct 1950 psig didn't make a noticeable change in engine running.

I have never had any trouble removing the heat shields w/ a magnet. They do need to face the right way. There is a slight counterbore that fits against the injector bottom, w/ the engine side sloped. I re-used some a few times when I didn't have new ones, I just sanded the sides smooth. I can't recall if they make a pressure seal w/ the end of the injector, i.e. also serve as a "crush washer".

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

I don't have any dates or Engine Numbers but at one time there was reusable plates that went in their as heat shields.

Concerning expense. As I said VW Rabbits used the same Heat Shields especially if you are using new Nozzles.
The VW Rabbit Heat Shields have a 5mm hole in them (that is what was in My 84 300D when I removed the Injectors and I also replace them with the same heat shields with 5mm holes).
However, over the years they started selling heat shields with 10mm Holes in them.

No one has explained why the hole size was changed. But one thing is good about it. You can use the 5mm hole ones on new nozzles.
If you have your car long enough for the Injectors to need removal again you can switch to the lager hole ones and it will seat on an unburned area of the Old Nozzles if you were able to reuse the old nozzles.

Personally I bought like 25 of the heat shields with small holes when the were cheap as I have 2 vehicles that use them and they are expensive if you buy the locally.

Anyway the VW Rabbit or Volvo Diesel (6 Cylinder D24 Engine made by VW) heat shields might be had at the VW Dealer for less.

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84 300D, 82 Volvo 244Gl Diesel

Might be the reason it didn't run too smoothly when I gave it a test run.

Yes, it says on the housing. I am in Sweden, so I very much doubt that there are anyone nearby.

Was thinking about making a pop-tester, but that'll be a later project.