Thickness does not matter, it doesn't conduct all the heat, only some. Look at nozzles that had a proper washer and ones that did not seal. The ones with reused washers will be discolored blue from heat damage and have a poor spray pattern.

at idle, combustion occurs ~6 times per second in each cylinder. How fast can heat be transferred to the head through this washer?

ps - my camera sucks lately

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Diesel911 - that would be a rail pin in #3. I guess it won't work for the larger diameter shields.

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Heat is not a "number of times per second" thing.

They are called HEAT SHIELDS for a reason!

I'm sorry.

I forget that the simplest questions asked on the internet get people all worked up about being right.

I appreciate everyone's contributions!

In the meantime, I get to take all the 'right' parts and condense them into the real stuff!

Thanks for all the replies, you guys are the best instructors ever!

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83 300SD, Euro Delivery, Mesa Red, 275k, running strong & quick.

Stop Struggling and get free.

Heck, this aint a fight. You should see some of the good ones.. lol This is more of an analytical discussion between two people that know a lot more than I do.

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79 MB 280 SEL Euro 133k
77 MB 450SL 154k
05 Mustang GT Vert (3) 104k
12 TSX Wagon Tech (66k) (192k)
06 Subaru Outback base (135k) 164k
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04 Honda Pilot 292k
1967 Mustang (Resto Project)
1968 Mustang (Parts Bin)
00 Ford Ranger 124k

If the Rail Pin is part of the Timing Chain Tensioner Rail; I have not had that part of the Engine apart yet.

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84 300D, 82 Volvo 244Gl Diesel

If you look at a high mileage set of Spary Nozzles you can see that the area between the Injector Pintel is clearly erodded away by the heat of combustion and the area covered by the Heat Shield is protected. So the Heat Shield works.
What I ment by my last post was is that you can run the Engine with the Old Heat Shields with no obvious damage until you can get some new ones.
Back in 92 when I bought my Volvo Diesel I rebuilt the Injectors and did not even remove the Heat Shields as I did not know they should be replaced. They did not get replaced for 1 1/2 years.
When the Injectors were pulled there was no signs of overheating or carbon getting past them either.
I had a learning curve that I had to go to with the Volvo. Now that I know they sould be changed I change them. (I was not on the internet back then.)

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84 300D, 82 Volvo 244Gl Diesel

I've seen two different heat shield used as in the photo. Is there a difference in application?
I've gotten the small opening type one time and the large opening type on other. They both fit my 300D. My part supplier hasn't been able to answer this one.

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DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012

As people have mentioned, part of the function of the heat shields is to make a good conductive heat path between the injector and the cylinder head.

If there is a large thermal resistance between the injector and the head, the injector will overheat, and the needle will blue, and fail.

So, what's important in making a good thermal contact, and how can you acheive this off the end of a production line without special fitting and lapping operations?

What you do, is to make a washer which crushes and conforms to the two surfaces during installation. To an extent, it will allow a relaxation in geometric tolerances and surface finishes while still giving a low thermal resistance.

This is why the heat shields are a use once device - they will never conform to the two surfaces, injector and head as well again, as they have already been crushed once.

As you tighten an injector down, and the small thin projections of the heat shield crush, they form intimate contact with the injector body, and as they crush, the contact area increases. Owing to the plastic deformation, this is a once only process, and if you tried to re-install one, you would not get a good even contact - you would get really solid contact at at least one point in the circumference as the torque wrench clicks out, but, you won't get good thermal contact for all 360 degrees like you would with a new one.

I needed to reuse a few since I was short a few new ones. I did manage to push the center ring back by using a few small sockets in a vice. I am going to replace the shields with new ones s soon as I have a chance. It will be interesting to see how well they worked for the short duration.
I did reuse them in the past without trying to reform them and soot got up in between the lower injector body and nozzle.

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DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012

Ok boys and girls, which blue triangle do you think moves heat away from the red hot block fastest?

Mr. Cruncher? you had your hand raised first.

can you also tell us which of the blue triangles best models the relationship of the heat shield to the injector nozzle body?

VERY GOOD!


Lets move on down the page, shall we?

OK... Mr. Induction, your turn! Which black box is best protected from the fiery red flames?


now, since the larger diameter heat shields are an older design, why do you think successive models narrowed the hole?? hmmm?? Doesn't that also decrease the surface area touching the injector nozzle - reducing heat transfer....hmmm?

but--- it certainly 'shields' more of the injector's surface area from the fiery red flames.

well its been fun, but story time is over.

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I will not respond to such a puerile post. Grow up, then we'll try to have an adult converstion and maybe you'll actually learn something.

IDI VWs use the ones with a smaller opening. From the pictures in repair documents it seems Mercedes used the ones with the large opening. Considering the injector nozzles and bodies are the same on both cars I assuemd it had something to do with the swirl chamber / prechamber differences.

-J

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

Thanks for the intelligent, thorough, metallurgically and mechanically accurate response. I commend you for such. This makes perfect sense and is relatively indisputable as the correct, complete answer.

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83 300SD, Euro Delivery, Mesa Red, 275k, running strong & quick.

Stop Struggling and get free.