Do I Have Injector Heat Shields In My Prechambers, And If So, How Do I Get Them Out? - PeachParts Mercedes-Benz Forum

Squiggle Dog · #1 08-13-2010, 10:22 PM

This afternoon I decided to install the rebuilt injectors in my 1968 W110 200D OM621. I got a pick set out to remove the old heat shields (crush washers). Either they are really stuck (the pick is bending) or there are no heat shields installed. What is your opinion? If there are heat shields in there then they are very different looking from the new ones I purchased (last picture). If they are in there, how do I get them out?

glenlloyd · #2 08-13-2010, 10:37 PM

From the look of it I would say yes, you have heat shields in there, but based on the picture of your new heat shield they look to be the wrong type, but it's kind of hard to tell. I think you need to take a swab or cloth in there with some cleaning chemical to clean off the goo that's at the bottom.

If there aren't any heat shields in there then there's a problem in the sizing of the orifice on the new heat shield, it shouldn't be bigger than the hole at the in the pre-chamber, otherwise the void between the two just ends up filling with carbon.

I have some heat shields that are supposed to be for that engine I'll take a pic and you can compare etc.

my .02

Steve A

Hit Man X · #3 08-13-2010, 10:43 PM

Stick a pen magnet in there and see if anything comes up.

But it appears to be equipped with them.

Fattyman · #4 08-13-2010, 10:45 PM

They look like the wrong ones to me too. Use some Hoppes gun cleaner to clean the carbon off of the pre chamber. Don't let it go down the hole if you can avoid it.

vstech · #5 08-13-2010, 10:52 PM

yep, you have shields in there, and LOTS of carbon. use the pic and scrape around the outside edge of the shield. get all of the carbon out of there, spray some pb blaster or aerokroil and let it soak and tap on the shields with a screwdriver to loosen them.

glenlloyd · #6 08-13-2010, 10:55 PM

Here's a picture of the heat shield I show for this engine. Size of the orifice is 7.5mm. BA lists this as suitable for the 200D.

steve a

As a side note, the heat shields in there look more similar to VW IDI heat shields, I think they have a small orifice, like 5mm.

Squiggle Dog · #7 08-13-2010, 11:11 PM

Thanks for the advice, everyone! So, after doing some research I have found that there are indeed heat shields in there. They are the original T-style and are probably fused to the prechambers.

I should be able to remove them either with a slide hammer, jamming a screwdriver into the hole and prying/twisting, or inserting a round file or screw extractor into the hole and twisting/prying.

I have also read that unlike the new design heat shields I purchased, these CAN be reused over and over. I think it may be a good idea to use them again IF I can get the contact surfaces clean and smooth. Perhaps I could polish the surfaces with lapping paper that is intended for rebuilding injectors or a paste polish. It would obviously not be a good idea to reuse heat shields of the current design.

The factory service manual says to tighten to 7-8 MKPS. This may change when using the updated heat shields.

So, what do you think? Clean up and polish the surfaces of the original heat shields and reuse them or get violent with the tools and remove them from the car and install new ones that are a one-time use? I am leaning toward the first option!

Squiggle Dog · #8 08-13-2010, 11:12 PM

Quote:

Originally Posted by glenlloyd

Here's a picture of the heat shield I show for this engine. Size of the orifice is 7.5mm. BA lists this as suitable for the 200D.

steve a

As a side note, the heat shields in there look more similar to VW IDI heat shields, I think they have a small orifice, like 5mm.

Those look like the ones I purchased.

vstech · #9 08-13-2010, 11:22 PM

I'd not use those shields again, get them out, and install the new proper shields. all that carbon is from reusing worn shields. don't do it.
clean really well, and tap on the outside edges of the shields, don't put anything in the hole that could go through and hit the glow plug or the q-tip shaped doodad that's in there. you don't wanna have to pull the prechambers out!

Diesel911 · #10 08-13-2010, 11:24 PM

If you do not soak them in something to soften the Carbon by the time you get them out they may not be reusable.

While the Heat Shields are out inspect the inside of the Prechamber.

glenlloyd · #11 08-14-2010, 01:19 AM

Quote:

Originally Posted by Squiggle Dog

Those look like the ones I purchased.

They do, except that the orifice on the ones you purchased looks like it's larger, something closer to 10mm. To be honest I don't know precisely what the factory specified. BA says these fit a broad application range but if you look at other parts suppliers they make a distinction.

If you jam a small screwdriver down into the existing heat shield and twist it from side to side you should be able to extract it.

steve a

MTUpower · #12 08-14-2010, 10:38 AM

Get a small net- stick it over the heat shield and turn the engine over a couple times-the shield ought to pop out.

Stevo · #13 08-14-2010, 11:51 AM

I have used a s/s welding rod sharpened with a short 90 degree bend to pull those suckers out.

Diesel911 · #14 08-14-2010, 12:14 PM

At my favorite internet part seller they showed 6170170360 as the part number for the Heat Sheids on both the 200D and my 300D. These are the disposable ones.

However, there is some posts on the Heat Sheild hole size somewhere.
Mine came with the 5mm hole size Heat Shields and the above parts seller sold me the 5mm holed Heat Shields is not selling the 7.5mm holed heat shields for the same application.

The Monark Nozzles I got from one of the sellers also came with the 7.5mm(or 7mm?) holed Heat Shields.

Since I prefer the 5mm holed Heat Shields the last time I ordered I used the ones for a VW Rabbit Diesel. (The Heat Sheilds for my Volvo Diesel; made by VW are the same as the ones used on the Mercedes.)

In the thread about the Heat Shields no one had any specific answer concerning the change in the Hole size.
However, it was suggested that if you were reusing Injectors with the Old spray Nozzles in them that using a different hole size from the previous one would allow the Heat Shield to make contact in a different area of fresh flat metal.