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  #16  
Old 03-13-2002, 07:36 PM
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Billybob,

1- The aftermarket gasket set I got was Victor-Reinz. The kit was very similar to the OE Mercedes kit, except the OE (dealer) kit had a MUCH nicer intake gasket, and very minor differences in the head gasket. The genuine MB kit was made by Elring. Pictures of the two side-by-side are here:

http://www.w124performance.com/images/OM603_head_replacement/

(scroll down to "head_gaskets")


2- Yes, the head is thicker up front in the timing chain area, which is why longer bolts are needed. This is explained in the OM603 service manual as well.

3- About the prechambers, re-read this thread from the top more carefully - it's confusing. The problem is in the MIDDLE of the p/c, where it tapers. That's where it's "hanging up". The sealing surfaces never touch because of this. This results in the p/c being too far up in the head. It needs to be lower. Material needs to be removed at the leading (wide) radius to allow it to seat fully. Using a spacer would cure the sealing problem, BUT it would result in the p/c being too far up! The spacers are ONLY supposed to be used when removing material from the sealing surface (flat surface up top), the area that needs to be "relieved" on the head will not affect the final position otherwise. Make sense now?

4- The alternate, easier, method is to relieve the p/c itself where the wide part starts to taper. Only about 0.5mm needs to be removed. Metric Motors said it *could* be done by hand, on a belt sander or grinder, but more accurately should be done on a lathe. There's plenty of material in this area of the p/c.

5- Another alternate solution would be to have the head sealing surface milled. Metric says about half of the new heads have poor surfaces out of the box. Removing some material off the face would require using the spacers to raise the prechamber, which would also lift them away from the pesky contact point at the taper. The downside to this is the cost. The "spacer" rings are ~$20/each from the dealer, and ~$16/each mail order. That's ~$100/set, PLUS the machining cost. And, possibly, the cost of new prechambers!

6- Prechamber price for "Balo" brand p/c's, they are the OEM for Mercedes:

$100/ea - local dealer (genuine MB part)
$60/ea - BenzBin
$60/ea - PartsShop
$55/ea - MegaParts
$43/ea - Wholesale Parts
(FastLane - no price shown, special order?)


HTH,

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Last edited by gsxr; 08-12-2007 at 11:51 PM.
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  #17  
Old 03-13-2002, 09:03 PM
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Wink Confused?

I apologize if so! I was looking through my 603 Manual and I found procedure 01-410 Refinishing the prechamber sealing surface. It appears that this procedure can be done with the head off or in place. In looking at it appears that the area of the prechamber bore that is conical forms the sealing seat for the corresponding conical tapered section of the prechamber. It is the mis-match between the prechamber and the bore that is failing to seal and allowing the leakage in your head? The threaded ring forces the prechamber into its' bore under compression sealing the prechamber outside contour to the recess bore shoulder. It appears that this procedure deepens the bore shoulder which allows a spacer to be placed into the bore followed by the prechamber itself. I haven't seen a spacer but I presume it will be flat on the bottom (to fit the newly cut recessed bore) and shaped to fit the outside shoulder of its mating prechamber. The locking ring will then force the prechamber outside into the spacer inside/top contour and the bottom of the spacer into the bottom of the newly cut bore recess. It appears that the spacer is performing a function similar to a valve seat, providing a sealing surface.

The depth of the cutting of the recess is done with respect to the distance the prechamber protrudes into the combustion chamber. A combination of material removal and spacer height will determine the depth of protrusion (7.6 -8.1 mm).

It would appear that changing the outside dimension of the prechamber to fir the bore recess would be possible but harder to accomplish accurately, it seems to me that the tapered shoulder of the prechamber and the tapered area of the bore recess are where the sealing action actually takes place rather than the upper lip or top portions of the prechamber. If so then it would take a lathe turning to accurately modify the prechamber outer dimensions and maintain its' sealing ability. As the prechamber is essentially a part of the combustion chamber and therefore subject to similar stresses it might be better in the long run to modify the bore recess in the head to fit the prechamber. Maybe if you had a single spacer to examine and trial fit to a prechamber it would allow you to know which method would be most appropriate. It appears that the resurfacing of this prechamber sealing surface is contemplated to be done more than once with the proper tool and the appropriate spacers.

If you don’t have the manual I’d be happy to email you the procedure if it would be any help. Thank you for your info, time , and patience.


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  #18  
Old 03-14-2002, 12:14 AM
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Hi Billybob,

Actually, the sealing surface is the flat area up at the base of the prechamber. The angled part does not form a seal. The wide section of the angled part is what is contacting the head incorrectly, since the bore is shallower on the new head. See the fuzzy upside-down photo below.

I do have the manual and have looked at the section you reference. That procedure trims the upper flat sealing surface, and the washer takes up the space removed by the reaming process. Normally, NO machining is to take place other than at that sealing surface. However, the new heads need to have the bored deepened at the angled part to allow the sealing surfaces to actually touch each other! Or, the prechamber can be milled. I ordered new prechambers and will measure the old vs. new when I get them. I pulled the old ones out tonight, and will get the new ones on Friday.


Hope this clears it up a bit...
Attached Thumbnails
OM603 - big compression leak at injectors/prechambers-prechamber.jpg  
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  #19  
Old 03-14-2002, 12:45 AM
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Unhappy Mea Culpa!

Thank you for the correction! So as far as the head is concerned the sealing surface in the bore may have been already cut to deep or the shoulder not deep enough for your present prechambers. Or, your prechambers are just to large in some dimension for this new head. Thanks again because like I said I'm anticipating this same issue and it will help very much to know what to expect, to look for ,and to ask for in this expensive and time consuming repair.
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  #20  
Old 03-17-2002, 02:05 PM
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OK, here's the latest, copied from my 2 posts to the diesel email list:

Thursday:
==========
I just got the new prechambers - a day early, too - but they don't work. I measured carefully. The important dimensions are identical. Interestingly, the top lip is about 1.7mm thicker. This makes the lockring sit that much higher away from the prechamber, but does not affect the seal/seat area. These are "Balo" brand p/c's, they are the OEM for Mercedes. The new ones drop into the head with almost zero finger pressure required. I tried using a string of "red" Plastigage on the seat and set one in place. There is at least a 0.05mm gap since the Plastigage wasn't even touched. Metric Motors (who have been VERY helpful, btw) suggested that the genuine MB part seems to work more often than the "OEM" part, even though they are made by the same company - weird. I'm not going to spend $480 to find out though (these were $260 + S/H from Rusty, btw.)

Right now, I'm thinking of grinding my old ones down and seeing what happens. I also want to investigate using the 3.5L prechambers, which are also used on the 2.5L OM602, IIRC. But I think since they are designed for 5-degree inclined injection that may not work, or may require the new lock rings, injectors, etc which is way, WAY too much money for me. If anyone has any other info, please let me know. I'll keep y'all informed as to my progress...




Friday:
==========

I brought all the old prechambers to my b-i-l's shop. He has a lathe there, and he set it up for me and told me to have a ball. I basically just beveled off the radius of the lower edge of the p/c. It's really hard to measure exactly what was done. I just eyeballed all of them, they were all pretty close. Pictures of new, old, and modified are at the URL below. I popped in one modified one and used a strip of the thinner Plastigage. This time it flattened completely! I wanted to check all 6, but the Plastigage was so embedded into the head seat I didn't want to clean up the mess 6 times - once was enough. I figured I'd take a chance and try them. All six went in uneventfully. I torqued them down to 115Nm plus a smidge. I also torqued the injectors to the top of spec, about 80Nm I think. Got them all sealed up and then cranked it over with the stop lever tied down. No more "puff puff" noises! So far so good.

I then buttoned up the rest (fuel hard lines, return lines, glow plug wires, etc) and tried the "real" test fire. To save the starter I would crank for 5-10 seconds at a time, then wait a bit before trying again. After the first few rounds the battery started getting weak. I plugged in my newly-acquired charger at let it charge at 60A for about 5 minutes, then continued. That helped cranking speed for the next couple of rounds. It finally was starting to catch on one or two cylinders but still took a lot of cranking to finally run on its own. I wasn't sure if I should have the pedal floored until it started to fire, or not. I didn't at first but later held it half way down to try to get more fuel up there faster. Don't know if it did any good.

So, it FINALLY lit up. I was starting to wonder if it ever would. It settled down and ran OK, other than a high-pitched rhythmic "ting ting ting" noise somewhere up top. Kind of like a little hammer on a wind chime. That really worried me. After a few minutes it went away though. (fingers crossed) I let it run for about 15-20 minutes, until the temp gauge reached 85-90, and I got hot air from the heater. I varied RPM from idle to 3000 or so and put on some accessories to try to give the engine a little load. I shut it down, then re-started it, and it fired instantly. I observed no obvious leaks but time will tell in that department. I'm very curious as to what the power difference is, if any. But I can't tell until my brake pads return. Grumble. I don't want to run it in the garage, with no load, just to carbon up the freshly cleaned prechambers. So it will sit silently for a few more days. In the meantime I can clean up my mess and start planning for doing this job to the OTHER car. (Ugh.)


More photos are at the URL below:

http://www.w124performance.com/images/OM603_head_replacement/
Attached Thumbnails
OM603 - big compression leak at injectors/prechambers-prechamber_mod1.jpg  
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Last edited by gsxr; 08-12-2007 at 11:51 PM.
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  #21  
Old 03-17-2002, 02:07 PM
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Here's a close-up shot of the new Balo prechamber, and one of my old ones that I milled down on the lathe:
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OM603 - big compression leak at injectors/prechambers-prechamber_mod2.jpg  
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  #22  
Old 07-30-2002, 01:34 AM
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Quote:
Originally posted by gsxr
Are you sure about that? The bottom of the injector is flat, the sealing face of the prechamber appears to be conical. And I'm pretty sure the old ones were in the same way...
The image in section 07.1-230 of the CD manual is clear enough to show the injector seals with the conical face up and I suppose the flat side down. That's how mine were although I have records that show the injectors have been replaced.

Does anyone know for sure?

Thanks,
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  #23  
Old 07-30-2002, 09:36 AM
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Yes, the flat side goes against the flat injector face, and the curved/conical side goes against the prechamber. Place one of the washers ("heat shields") on the injector face, it's pretty obvious which way it should go. It fits nice and secure with the flat side touching, and evenhas a little recess to "locate" it on the injector. The other (curved) side doesn't fit properly at all, just floats around on top. Make sure you have the correct washers, the older ones are claimed to interchange but I found they didn't. The old style washers (p/n 617-) have a bigger hole in the middle, the newer (60x-) ones have a smaller hole.

Remember, this had NOTHING to do with my original post & problem, that was the sealing between the head & prechamber, NOT the prechamber & injector. Just wanted to make that clear.


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  #24  
Old 07-30-2002, 04:06 PM
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That was a pretty good trick by itself... putting it in a lathe and turning it down.. and it winding up " milled " (as per the second picture).... This has nothing to do with the original post either ...
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  #25  
Old 08-12-2007, 11:18 PM
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gsxr, your pic link is down, could you repost it or send me pics so i can host them?
I may be doing this job soon and will need all the help I can get.
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  #26  
Old 08-12-2007, 11:21 PM
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also, is all of this prechamber business needed if you buy a used 17+ casting head complete? Or is this only necessary for bare new heads?
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  #27  
Old 08-12-2007, 11:37 PM
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If you get a 17-up head with prechambers, you can keep the prechambers but you'll need injectors that work with those prechambers. Your original injectors won't screw into the newer prechambers.

Sixto
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  #28  
Old 08-12-2007, 11:41 PM
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Or you can buy a new $et of prechamber$ and injector$

$ixto
87 300D
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  #29  
Old 08-12-2007, 11:55 PM
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I fixed the links - thanks for the heads-up.

If you replace a #14 head with a #17 or newer, and plan to re-use the original 1986/87 vertical prechambers, you have a 50/50 chance of having this problem. New vertical prechambers will NOT help. You can avoid the problem entirely by converting to angled/inclined prechambers AND injectors, but unless you get them free with the used #17 head, it's just too expensive to switch.

There are no complete new heads - only bare heads. A new #22 head is $2000 list, $1600 wholesale. The #22 is nice because it has the improved oil galley in front of the #1 cylinder (see photos at the links above).

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  #30  
Old 08-13-2007, 09:21 AM
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Sorry I'm being dense here.. could you show me the improved oil galley? I'm not seeing any pics that show that.

Also, is this something that could be improved on the 17 head with a drill press and patience, or a good machine shop??

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