Hello All,
I have been hard at work, and making good progress with this car mostly due to searching this forum. Thanks to you all! I have come across a problem that I cannot successfully search. There are many related posts, but no definitive answer. I recently sent my injectors off to be rebuilt, and this quieted the car down enough for me to realize that I am puffing air past the prechamber ring. It is NOT leaking between the injector and the chamber, it is definitely coming past the chamber and ring. (Verified with some strategically placed PB Blaster) I am not sure if it has done this since I owned the car (End of February) I think it was there, but may have worsened after after R&Ring the injectors. I still think the overall quieter engine unmasked this.
This brings me to my question. I read posts about "resealing" the prechambers, but no one goes on to say exactly how. I did read gsxr's great post about modifing prechambers to fit his new head, but I still have the same head and chambers the car came with (as far as I know).
In the sevice manual it desribes slightly machining the surface of the head where the prechamber seals with a "Countersinking Tool" and then installing shims. This tool is almost like a hand powered end mill with a replaceable cutter head that threads in place of the threaded ring and machines the surface on the head where the prechamber seals. This is done with the prechamber removed, of course, and the shaft that runs the cutter head is turned by a tap-handle. I searched out a couple of these tools, and they run about $525.00. (For Crissakes McDuff!!) I would like to avoid this if possible. I see the slide hammer and the splined socket in the rental pool, but the "countersingking tool" is nowhere to be seen. (and who could blame the owner of one....not me!) The prechamber could possibly be cracked (form what, I know not) I plan to Pull it, and clean it up, but if it is not cracked, I would like to go in there with a game plan to get this thing to seal. Any suggestions will be greatly appreciated, and if successful I will add this to the Wiki. I think more people have this problem than they are aware of. All of mine bubble just a little, but this one is huffing. I will go through and fix them all if I can get #1 to seal up.
Thanks Again,
JDC

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1990 124,128 602,962

Beware the hobby that eats.
Benjamin Franklin

Maybe the use of a thin shim will help it seal.

you have to weigh the effectiveness of pulling the prechamber and attempting to re-seal it with the head on the block. Consider the bubbling, how much compression are you losing?.. not much.

the huffing: If you are really concerned, try tapping it back in and tightening it up first before you go to the extremes of honing the mating surfaces (craziness).

Word from a local shop is that they use some kind of metal to metal sealant and do not like the idea of putting shims on the prechambers. (they were reluctant to give up their trade secret though)

If you have space, try to tap the prechamber ring with a screwwdriver and a hammer (lightly!!) If it moves at all from a gentle blow, you know its loose and hopefully setting the prechamber back down a bit will stop the huffing.

Just some thoughts.

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I would be inclined to pull it out clean everthing and make sure it is torqued correctly and see what happens.
As far a sealants go Loctite makes a lot of things that go way beyond what you see at the local Autoparts store. I am sure they have a web site.

A partial Quote form one theo3000; "I tried ThermoSteel to patch the holes (to patch hole in turbo exhaust housing), and I needed to re-apply the patch a few times due to improper curing, but after I finally gave it enough time and some..."
Here is his post:
ThermoSteel
You might find the web site and see if it is suitable for sealing.

Added I got curious and went to the ThermoSteel web site.
http://www.afcinternational.com.au/site/data/18003_tech.htm
One of the applications listed in the web site.
"THERMOSTEEL can also be used to fill holes and pits in heads, blocks, and manifolds."

I am also wondering if the Secret Sealant at the shop mentioned in the other post is nothing more than low tech Muffler Cement found in Auto Parts stores.

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84 300D, 82 Volvo 244Gl Diesel

it sure sounds good.

Even JB Weld is an option if you coat each surface with an oil / wax. At such a thin application might not provide the typical adhesion.

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Thanks for the replys so far. I am not sure sealant of any type will help much. The boss for the threaded ring seems to have a groove machined into it, and that is where the compression is leaking from. Any sealer around the threads will fail here in short order. Keep Em' coming!

__________________
1990 124,128 602,962

Beware the hobby that eats.
Benjamin Franklin

I'm not sure you're understanding the suggestions completely. Or perhaps you have not explained your issue clear enough.

do you understand how the prechamber is set in the head?

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Take a look at the diagram at tha below site and take a look at item #173 that is the Pre-combustion chamber. If you notice in the pic the top of the Pre-combustion chamber has a lip/flange at the top that is larger than the rest of the Pre-combustion chamber.
The sealing area is under the bottom surface of that lip/flange and where it makes contact in hole in the Cylinder Head. Any, sealant used would go on one of those surfaces.

Item #179 is the part you called "the threaded ring having a machined groove in it", that part only serves to push down the Pre-combustion chamber and is not made to seal around th threads.


http://www.detali.ru/cat/oem_mb2.asp?TP=1&F=124128&M=602%2E962&GA=722%2E418&GM=717%2E437&CT=M&cat=502&SID=01&SGR=065&SGN=07


In the pics below left is the a Pre-combustion Chamber pulled out with Red Arrows showing the sealing area on the Chamber it self. The right pic is showing the Pre-combustion Chamber installed in the head with Red Arrows pointing to the same sealing area (this is where the sealant would go). The Gree Arrows point to the Threaded Ring with the groove that holds everthng together.

Item #110 in the right pic sits between the Pre-combustion Chamber and the Locking Ring (boss with the groove). I suppose it is possible for it not to seal where it makes contact with the top of the Pre-combustion Chamber but so far I have not read about that.

Attached Thumbnails

   

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84 300D, 82 Volvo 244Gl Diesel

MB offers 3 sizes of pre-chamber shims for the OM60_series engines.

I would try the thinnest shim as a thick shim might move the pre-chamber up too far.

MB number 601-017-04-60 is 0.3mm thick.

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

While I think adding a thin shim most likely be safe to do; I also think it may or may not work.
If the sealing surface on the head is not flat as it is supposed to be a shim will not change that. Being a shim they are not supposed to compress much so the could not be expected take up for an uneven surface issue.

The next thing also may or may not be a problem is that the projection of the Precombustion Chamber into the Cylinder Head would be changed from stock projection. The only way to properly measure the projection is to remove th Cylinder head. There is a small chance the the Precombustion Chamber is already as high up in the Cylinder Head as it is supposed to go.
If so putting any shim under it would not be a good idea.

Using a sealant has the advantage of not changing the protrusion of the Precombustion Chamber.
Also If you use a sealant and it does not work you have done no harm to the Cyinder Head.

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84 300D, 82 Volvo 244Gl Diesel

Here is a site with the pdf
Refinishing precombustion chamber sealing surface
http://www.ps2cho.net/downloads/MB%20CD/W124/w124CD1/Program/Engine/602_603/01-410.pdf
More:
http://www.ps2cho.net/downloads/MB%20CD/W124/w124CD1/Program/Engine/602_603/01-417.pdf

http://www.ps2cho.net/downloads/MB%20CD/W124/w124CD1/Program/Engine/602_603/01-416.pdf

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84 300D, 82 Volvo 244Gl Diesel

That is a common problem.

The pre-chamber protrusion from the factory is 7.6mm-8.1mm & a 0.3mm shim isn't going to make enough difference on a 17 year old engine at all.

Have installing 100+ shims on those engines, including engines with less than 10K miles that would be the best thing to START with.

BTW that is 0.0012"

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

Thanks guys,
I think I'm gonna take a swing at the shim. BTW is that a dealer only part, or might I be able to order it elsewhere. The closest dealer is 250 miles away.

__________________
1990 124,128 602,962

Beware the hobby that eats.
Benjamin Franklin

Diesel 911, I do understand how they are seated in the head, but everyone started talking about thread sealer. I thought you guys actually wanted me to try to seal it at the threads. Now I see what you were saying.

__________________
1990 124,128 602,962

Beware the hobby that eats.
Benjamin Franklin

Call Phil or Roy

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RRGrassi


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