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  #1  
Old 05-10-2009, 12:22 PM
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My injectors didn't have heat shields

This is for my '74 240D. I got some rebuilt injectors from bgkast and installed them yesterday. A new set of heat shields came with the injectors. Well, I got the old injectors out, and this is what the bottom of the hole looked like:



It doesn't look anything like a heat shield down there, so I dropped a new heat shield in the hole and it looked like this:



I put the new injectors in and torqued them to 50 lb-ft and I've got no leaks so far, it has only been a day though.



Here's what the ends of the old and new injectors look like.



I was hoping to cure the huge plume of smoke that I'd get on a cold startup, and the loud rattling/nailing sound when the engine was idling. Well, I think it lessened the smoke, although I need to start it on a chilly morning to be sure, and I don't know when we'll have another one of those any time soon. But the loud rattling is still there. I may be a little better, but sometimes it still sounds like I have rocks in the engine. Maybe that's just the way the w115's sounded? I'll try a diesel purge some time and start using straight biodiesel now that its warm.
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My injectors didn't have heat shields-injector-ends.jpg   My injectors didn't have heat shields-injectors.jpg   My injectors didn't have heat shields-hole-1.jpg   My injectors didn't have heat shields-hole-2.jpg  
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  #2  
Old 05-10-2009, 12:41 PM
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I'm surprised your old injectors sealed!

-J
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  #3  
Old 05-10-2009, 01:23 PM
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You can get steel-steel sealing if you crank it tight enough
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Old 05-10-2009, 02:41 PM
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tighten till it squeaks....
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  #5  
Old 05-10-2009, 04:05 PM
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Quote:
Originally Posted by Simpler=Better View Post
You can get steel-steel sealing if you crank it tight enough
That may have been the case. I used a cheater about 3' long and a considerable amount of force (I have an old sacrificial ratchet as a breaker bar and each time I thought the wrench broke) to break the old injectors free.
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  #6  
Old 05-12-2009, 02:54 PM
KCM KCM is offline
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Hate to tell you this, but the smaller shiny round piece in the picture of your injector hole is the injector seal, or "heat shield" as you call it. The old style was a round "T" shaped seal that slipped into the prechamber hole with the top of the "T" showing and is what the nozzle seals against. If you are using the new style one-time use crush-style "heat shields", you should remove this old style seal.

My OM621 had these, which I replaced with the new style. I wish I would have left the old style in, as they can be used over and over, while the new style should be replaced every time the injector is removed. I would take the injectors out, throw away the "heat shields", and use the original seals.

As for the rattling noise, my OM621 (which is a direct decendent of your motor) does that, usually when you first start the engine and till it warms up. There's a name for that problem, but can't think of it at the moment. It's an annoyance but hasn't caused me any problems in 100,000+ miles.
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  #7  
Old 05-13-2009, 04:38 PM
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Quote:
Originally Posted by KCM View Post
Hate to tell you this, but the smaller shiny round piece in the picture of your injector hole is the injector seal, or "heat shield" as you call it. The old style was a round "T" shaped seal that slipped into the prechamber hole with the top of the "T" showing and is what the nozzle seals against. If you are using the new style one-time use crush-style "heat shields", you should remove this old style seal.
Oh I tried removing what I thought was the heat shield/seal down there. I don't have a slide hammer, but one of those and a sturdy hook is the only thing that I could see getting that out of there. I tried prying with a screw driver and the handle end of a round file and nothing moved so I assumed it was the bottom of the injector hole. Will it hurt anything to leave the crush washer style seal on top of the old style seal? I'm keeping an eye on it and so far there's no leaks. If it does start leaking, I'll pull the injectors and take out the heat shields...so you're saying the new injector nozzles should seal against those old seals?
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  #8  
Old 05-13-2009, 04:49 PM
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thats definitely what he's saying.

And if you look at your injector tip (nozzle), you will see it has been properly protected from heat and pressure.
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  #9  
Old 05-13-2009, 05:12 PM
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There is a special socket and slide hammer for removal of your injector receptacles. The socket fits over the tangs of the locking ring (The big round thingie with the upright "ears") and the locking ring is removed. The glow plugs need to be removed FIRST! Then the special slide hammer threads into the receptacle and you remove the entire piece along with a few pieces of your elbow on the hood and that soft tender bit of flesh between your thumb and fore finger.

You can then examine the "mixing ball" on the end of the receptacle and soak the old seals loose in some carb cleaner, mineral spirits, what have you.

Clean the head holes with a wire bottle brush and a shop vac to get all the loosened soot.

You then replace the seal under the injector chamber, replace the receptacle (using just a slight dab of NeverSeeze on the threads), re-install and torque the locking ring, re-insert the glow plugs (you might have to undo one or two of the lock rings and twist the socket to receive the glow plugs) and then re-install the injectors.

Don't be surprised if you are missing a ball from the "mixer". Pretty common occurrence and you need to replace the socket. THIS can cause the "death rattle" at start-up and idle.
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  #10  
Old 05-13-2009, 09:52 PM
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Quote:
Originally Posted by Mike D View Post
There is a special socket and slide hammer for removal of your injector receptacles. The socket fits over the tangs of the locking ring (The big round thingie with the upright "ears") and the locking ring is removed. The glow plugs need to be removed FIRST! Then the special slide hammer threads into the receptacle and you remove the entire piece along with a few pieces of your elbow on the hood and that soft tender bit of flesh between your thumb and fore finger.

You can then examine the "mixing ball" on the end of the receptacle and soak the old seals loose in some carb cleaner, mineral spirits, what have you.

Clean the head holes with a wire bottle brush and a shop vac to get all the loosened soot.

You then replace the seal under the injector chamber, replace the receptacle (using just a slight dab of NeverSeeze on the threads), re-install and torque the locking ring, re-insert the glow plugs (you might have to undo one or two of the lock rings and twist the socket to receive the glow plugs) and then re-install the injectors.

Don't be surprised if you are missing a ball from the "mixer". Pretty common occurrence and you need to replace the socket. THIS can cause the "death rattle" at start-up and idle.
I follow you. Although sounds like more than I really need to do. How about I remove the injectors, remove the crush washer heat shields, check the integrity of the mixing ball with a boroscope or something, and replace the injectors using the old (reusable) seals that are down there?

Oh, and what would be the harm of leaving the old seals in with the new crush washer seals on top? The only thing I can think of is the crush washers are shaped to fit the bottom of the injector hole, and that's probably without the old seals in place. Anything else?
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Old 05-14-2009, 08:55 AM
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Quote:
Originally Posted by pizzachef View Post
I follow you. Although sounds like more than I really need to do. How about I remove the injectors, remove the crush washer heat shields, check the integrity of the mixing ball with a boroscope or something, and replace the injectors using the old (reusable) seals that are down there?

Oh, and what would be the harm of leaving the old seals in with the new crush washer seals on top? The only thing I can think of is the crush washers are shaped to fit the bottom of the injector hole, and that's probably without the old seals in place. Anything else?

WHAT??? You're passing on the chance to get absolutely filthy, nasty greasy?? What kind of old Benz owner are you?

I doubt you could see the ball with a scope due to the amount of soot and gook which will be present in the chamber. I'd just remove the crush washers and slip the injectors over the old seals. You don't want to use the crush washers over the old seals because they are designed to fit into the relatively flat area in the socket. The old seals have a "pocket" which is shaped to fit the injector tips. If you don't have any fuel leaks using the old seals then you're good to go.

Rattle? WHAT rattle? That's just your baby clearing its throat waiting to turn loose those ferocious 72 horses!
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  #12  
Old 05-14-2009, 12:16 PM
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I had a lone heat shiels that was stuck and I got it out with a hook made from a coat hanger. If that didn't work, my next Mcgyver trick was to use a long self tapping sheet metal screw. I think that would get the most stubborn heat shield out.
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  #13  
Old 05-14-2009, 04:31 PM
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Quote:
Originally Posted by pizzachef View Post
Oh I tried removing what I thought was the heat shield/seal down there. I don't have a slide hammer, but one of those and a sturdy hook is the only thing that I could see getting that out of there. I tried prying with a screw driver and the handle end of a round file and nothing moved so I assumed it was the bottom of the injector hole. Will it hurt anything to leave the crush washer style seal on top of the old style seal? I'm keeping an eye on it and so far there's no leaks. If it does start leaking, I'll pull the injectors and take out the heat shields...so you're saying the new injector nozzles should seal against those old seals?
You should ALWAYS use new shields. They are a buck each for christ sakes. They are crush washers, one time use.

The easiest way to get those puppies out is to turn over the engine. Just dont be in the way they shoot out. I haven't been hit by one but they come out fast enough to make me stay worried.

PS I have the prechamber ring tool and the slide hammer adapter for rent (dep + mail + 6pack of beer).
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  #14  
Old 05-16-2009, 12:17 AM
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Originally Posted by winmutt View Post
You should ALWAYS use new shields. They are a buck each for christ sakes. They are crush washers, one time use.

The easiest way to get those puppies out is to turn over the engine. Just dont be in the way they shoot out. I haven't been hit by one but they come out fast enough to make me stay worried.

PS I have the prechamber ring tool and the slide hammer adapter for rent (dep + mail + 6pack of beer).
It appears the kind that are in my engine are an old style and are reusable. I unknowingly put the crush washers on top of them, so I'm going to remove the crush washers and give that a try...that's how its been for the last who-knows-how-long. And I did crank the engine...quite a bit..to try blowing the old seals out. They didn't move, I just heard air rushing out.

But if I need to remove the prechambers, I'll hit you up for those tools. I'll send you some local PA beer
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