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  #1  
Old 11-17-2009, 01:51 PM
Ian White's Avatar
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Out of curiosity; Injector Heat Shields

Out of curiosity, what would occur if one removed the injectors but re-used the old heat shields, I always replace them, but I see everywhere, "replace them, they are a one time seal..." What happens if you dont replace them? Just our of curiosity

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  #2  
Old 11-17-2009, 02:10 PM
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What happens is that combustion gases will go where they are not supposed to- that is along the bottom of the nozzle. I would imagine that the nozzle is cooled by fresh diesel (from inside) and can't take the extra heat.
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Old 11-17-2009, 02:41 PM
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When I fist got the Volvo I rebuilt the Injectors and reused all six Heat Shields. At the time I did not know they neede to be changed.
I drove for over 1 year like that until a Screwdriver Fell into my timing Belt and Pistons contacted Valves.
The new Head Gasket came with the Heat Shields. At that point it dawned on me that they should be changed.

What is interesting is that most diesels with Pre-combustion chambers or Swirl Chambers use a Copper or Aluminum Crush washer that seals on the Bottom of the Injector Nut exposing the end of the Injector Nozzle and part of the side.
They also run fine.
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Old 11-17-2009, 03:16 PM
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In working through a nailing problem with my 220D, I found my injectors had no heat shields. The PO had left them out. The injectors were heavily eroded around the hole, and that part (the nozzles as the shop called them) had to be changed. So I think the shields preclude that erosion. Ron
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Old 11-17-2009, 03:28 PM
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I think they still erode around the hole, even with the heat shields working properly , after many many miles. The shields minimize it.
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Old 11-17-2009, 03:37 PM
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Correct me if I am wrong, but I think because they are also referred to as "crush washers", that when the injector is reinstalled and torqued, they deform to provide a seal between the injector and precombustion chamber. If the injectors are removed, there is no guarantee that the faces will align the exact same way before the injectors were removed and thus provide a proper seal. As well as they are a minimal investment compared to new or rebuilt injectors. Thus the mantra "replace, replace, replace...".
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Old 11-17-2009, 03:40 PM
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What can happen is that soot will get past the washer, and then get into the threads... making the injector very hard to remove.

-Jason
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Old 11-17-2009, 04:23 PM
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also

Quote:
Originally Posted by compu_85 View Post
What can happen is that soot will get past the washer, and then get into the threads... making the injector very hard to remove.

-Jason
I think it was mentioned, small amounts of fire and streams of hot gas.
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Old 11-18-2009, 01:12 AM
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Quote:
Originally Posted by compu_85 View Post
What can happen is that soot will get past the washer, and then get into the threads... making the injector very hard to remove.

-Jason

Even with new Heat Shields I put a Never-Seeze type compound on the threads. If it does nothing else it helps perevent rust from building up in that area.

Having New Heat Shields is most likely most critical on the Turbo Charged Engines.

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