Diesel injector heat shield nightmare

JHZR2

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Had gotten my injectors rebuilt for my 91 300D. Time to install, and the heat shields are to be replaced. I pulled four of the five straight out. No problem….

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The last (rear) one? Magnet wouldn’t get it out. Tried a pick. No luck. Started looking for options, read a variety ranging from screwing a lag bolt into the hole, jamming a screwdriver into it, etc. The most plausible were to use an awl or punch to tap around the heat shield to break the carbon loose (with the help of a penetrant). No luck.

The shield started to become disfigured even when just pulling on it.

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Kept trying. Had hoped to work it loose, or able to move at all. Eventually I even tried drilling, cold chisel, punches, no luck at all.



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So now I’m screwed. Really hoping I don’t need to pull the head. I think I can just pull/replace the prechamber. It takes a splined socket and then a slide hammer threaded into the injector threads in the prechamber.

Maybe I was too heavy handed. But it wouldn’t budge with progressively more aggressive approaches. Should I have tried heat? I had already wet everything in a lot of penetrating oil.

Knock on wood I’ll be able to get the prechamber out. With my luck it will be seized in there too. How four went so well and the last one didn’t is annoying and frustrating.
 
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What you have done now is expand the metal, thereby making it tighter in the bore. I can only see one way to get this out now, and that's to make small cuts from the middle out to the edge. This will allow room for the heat shield to move back in away from the walls of the bore. If you are really careful, you might be able to use a small drill to cut away some metal, but it would be hard to tell when to stop.
A dremel tool might work, or even a really small VIBRATORY saw with a metal cutting blade, or abrasive tipped blade.
 

JHZR2

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you need to dissolve the carbon, spray brake cleaner around the washer, then try this tool


That was the first thing I tried. I have those tools for cluster removal. They didn’t work for this. They either bent the heat shield or slipped.


Looks good. The issue will be after messing this much, I think I’m best off pulling the prechamber anyway, if for nothing else then to clean any metal shavings out…

What you have done now is expand the metal, thereby making it tighter in the bore. I can only see one way to get this out now, and that's to make small cuts from the middle out to the edge. This will allow room for the heat shield to move back in away from the walls of the bore. If you are really careful, you might be able to use a small drill to cut away some metal, but it would be hard to tell when to stop.
A dremel tool might work, or even a really small VIBRATORY saw with a metal cutting blade, or abrasive tipped blade.

Yeah I realized that when I started hitting harder. Thing was, it didn’t work with light taps to break the carbon.

I’m beyond frustrated. Even if I can get the washer out, I think I still need to do a prechamber replacement.
 
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At this point, you probably do need to replace the pre chamber. But I have to say, you are now at the top of the list for the PLASTIC HAMMER AWARD! :D
Plastic Hammer.jpg
 
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That was the first thing I tried. I have those tools for cluster removal. They didn’t work for this. They either bent the heat shield or slipped.



Looks good. The issue will be after messing this much, I think I’m best off pulling the prechamber anyway, if for nothing else then to clean any metal shavings out…



Yeah I realized that when I started hitting harder. Thing was, it didn’t work with light taps to break the carbon.

I’m beyond frustrated. Even if I can get the washer out, I think I still need to do a prechamber replacement.

Take a break from it, the more frustrated you get the deeper the hole gets. With that shield in there you may not get full thread engagement for the tool to slide hammer the chamber out, that would be real problem if they got buggered. Sometimes removing the glow plug so you can remove the pre chamber can go all wrong if the tip is bulged.

Personally I am not of fan of removing a 5 cyl MB diesel cyl head if I don't have to, work on the heat shield first. If you can get it out use a piece of hose jury rigged into a shop vac and vac it out with the heat shield removed. You should be okay.
 

CleanSump

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Pulling the prechamber isn't hard if you have the right adapter for the threads and a slide hammer. I had a cracked prechamber once.
Note though, the prechamber is closed on the bottom side, just small holes in it. It'll be easier to work with out of the car in a vice.
Fancy puller here, but you can get very basic ones on ebay that work
https://www.airprotool.com/impact-extractor-for-pre-chamber-for-mercedes-engines-aet-00552.html

Not sure if the bottom of the prechamber can be unscrewed. I didn't try; just changed it and threw the old one away.

prechamber.jpg
 
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Its all good but reality can be much different like removing the heat shield. I suspect that cyl pre chamber may be badly carboned up, it could be a real bear to remove. I had one on an old 300d cause me all sorts of grief even with the OE MB tooling.
 

JHZR2

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Its all good but reality can be much different like removing the heat shield. I suspect that cyl pre chamber may be badly carboned up, it could be a real bear to remove. I had one on an old 300d cause me all sorts of grief even with the OE MB tooling.
Yeah that has me concerned too. That’s all I need is to have that Prechamber be stuck and then I need to remove the head. But I guess what choice do I have at this point?!?

I’m picking up a spline socket, slide hammer, and prechamber.. maybe the type you linked to will grab and pull it out (knock on wood), but if not I’ll be ready.
 

JHZR2

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Tried that tool.

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Really neat little setup. Not sure if I’ll need it again, but worth the gamble even though I have the OE tool…

But it didn’t get enough purchase on the buggered washer.

Time to pull the prechamber!
 

JHZR2

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Can’t say it’s going great… having a hard time getting this to move. Ugh. I really don’t want to have to pull the head. @Trav any hints??
 

JHZR2

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There’s metal shavings in there on the piston. Ugh!!!! Recommendations on next steps?
 
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My fear with metal shavings on top of the piston with the small access hole you have, is there's really no way of knowing if there's metal shavings that are in areas you can't see or access to clean up. If they find their way down the bore between the piston and the cylinder wall you can have some serious problems when you fire that engine up and run it. I've seen it with rock hard carbon in small two and four stroke engines, metal is worse imo.
 

JHZR2

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My fear with metal shavings on top of the piston with the small access hole you have, is there's really no way of knowing if there's metal shavings that are in areas you can't see or access to clean up. If they find their way down the bore between the piston and the cylinder wall you can have some serious problems when you fire that engine up and run it. I've seen it with rock hard carbon in small two and four stroke engines, metal is worse imo.
Yeah there’s loose hard carbon in there too.

DB2EE041-8E90-4B72-A2DC-6369F027C7A2.jpeg


Ugh.

Using a magnet I got everything I could. I’m thinking to make a very thin vacuum hose and put that in there too. Then maybe crank the engine with the prechamber out.

I’d think that such small bits would either melt or flow out. That may injure turbo blades though…

Replacement of prechambers is something done in the factory service manual. But it doesn’t cover this BS enough…
 
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