606's can be a pita when it comes to glow plugs. I was helping my freind change his last week and only 1 came out! :eek: His is a 98 E300D with 150k on original plugs. We just left the other 5 in their, this summer the head comes off. But after seeing how simple of a job taking the manifold off is I would just pull the glow plugs and ream the holes every year. Simple job and much cheaper than pulling the head every few years.

Yes. However because of the nature of the hole (too tight) you cannot get at that area to weld material to it. Since we drilled to the point of the bevel, it wasn't sealing when we got the plug screwed in. The machine shop showed me the other holes. Between the bevel and the thread area, there was little or no carbon. Therefore, the conclusion was that it was the bevel that sealed the plug and the threads were to push the bevel of the plug against the bevel in the head. On a side note, another machine shop that had to take a broken off GP out, did so by drilling the prechamber out and then drilling the threads out of the GP and pushing it out.

From what I see, I am not sure that it is the carbon that was holdng my GP in. It was the steel on aluminum that welded itself together. The machinist advised me to put anti-sieze on the threads and the body of the GP but not the tip to prevent this mess occuring in the future.

The GP came out finally with one part having some thread. If you can imagine drawing a line from the middle of the threads on one side to the bevel on the oppisite side, that is what mine came out as.

In retrospect, I should have not drilled. You see, if I hit the angle right, it would be great. If not, you are screwed because you will be hitting the head. All the time we thought we were on target because the shavings coming out were largely magnetic so we thought we were all right. At a machine shop they would have the head on a bench and a drill set at the right angle and drilled.

Returned from the machine shop a little happier. The machinist was gone but the shop foreman said he got it to seat a little deeper by making another bevel. Tomorrow they will helicore the head. The bevel is all important because that is what will seal the plug into the head while all the threads do is push the plug against the head. Our previous drillings were skewed and so they cut the bevel which made sealing impossible. Had we attempted to seal it with the threads only, I am not sure that would work well.

Exactly.... So if you have a non-turbo OM606 there shouldn't be any problems since the entire engine, head and block are iron. Add some antiseize to the equation and one should not have any problems.

Since the bevel seals the cylinder, there should be no issue even if the entire GP was coated with antisieze. When I took out the GPs, #1, 3 & 4 were stuck. The others came out easy. #1 and 3 came out after spraying lots of PB Blaster and when they did, the squeaked like there was no tomorrow. Taking out the head and looking down the injector area, I don't really see that much carbon in the prechambers.

I think the tool MB made for this operation probably allows you to drill confidently using a fixture with the head in place. I cannot imagine being able to drill this myself without a fixture.

Once the head is off the engine and out of the car, why would anyone drill out the prechamber? Seems like an awful lot of precision machining. Is the prechamber in this head something that cannot be pulled out?

Thanks for keeping us all posted on this item. Jim

There were a few tools and inserts. However, none of the tools would allow you to drill at an angle like a machine shop drill. They were drills of different sizes and drill stops so you don't go too far. nothing to do with the angle of the drill entering. You could still drill at the wrong angle. Besides the inserts were M10 X 1.0 while the threads of the GP were M12 X 1.25. I don't know if it would have worked but the inserts that were supposed to be the threads for the GP was so small that the body of the GP would slide into the insert but there was no way in hell the insert would thread into the GP threads.

You cannot pull out the prechamber with the GP in the head, can you? They drilled a hole in the prechamber from the bottom so they could pry out the GP after drilling out most of the threads holding it in. Just repeating what they said.

NO! Non-turbo 606's have aluminum heads like all other 606's. Either that, or Mercedes has developed an amazing new steel alloy that looks like aluminum, weighs as much as aluminum, and has the same thermal characteristics as aluminum. You never know where all those R&D dollars (oops, Euros) go. ;)

Seeing as we are talking about German Cars, maybe we should change these GP threads to Mein GP Kampf. My GP Struggle.

Steel and aluminum
 

Some metals do not get along too well. That is why you use di-electric couplings when you attach a steel water heater to copper pipes.
Has anybody ever tried dripping vinegar on the glow plugs around the threads prior to removal?
I know it sounds crazy but I ran into a similar situation 20 years ago when I was rebuilding the front suspension on my 66 E-Type Jaguar. On the Jag, the lower control arms are attached to aluminum blocks with 3/8 inch bolts. The bolts were about 4 inches long and went through the blocks. I unscrewed the nuts but couldn't budge the bolts (even with a pretty big cheater bar). There were rubber bushings in there so I couldn't heat it up without setting it on fire.
I was always working on the car (Jaguars are like English motorcycles because you have to work on them one hour for every hour you drive them) and every job was a challenge. I had learned to stop by the local independent Jaguar garage and get advice each time I got into a jamb. When I asked how to get the bolts out of the mounting blocks I found out that the "secret" was to drip vinegar on the bolt every day for about a week. The vinegar breaks the bond between the bolt and the aluminum allowing you to get it out. The most important advice they had for me was to avoid putting any kind of penetrating oil on it because the oil keeps the vinegar from penetrating and breaking the bond. "If you do that you'll never get it out" they said.
After a few days of vinegar dripping, the bolts came out.
I am wondering if that would apply to the glow plug problem that a lot of folks are having and if anyone has tried it.
(I posted this to a similar thread on the MBCA forum.)

Since I didn't see much carbon holding the plug in place and the other 2 stuck ones came out with a lot of squeaking and the machinist report, it makes me believe my issue was the stuck threads. Further to that, the machinist said to coat the entire GP with the exception of the tip with anti-sieze because if the carbon does come past the bevel, it could clog up the threads and the space between the GP and the head past the threads. Can't hurt, can it?

Also, if I had taken out the head, firtst thing, it would have cost me $50 to remove the GP. Instead, I have to pay about $300 to make it work again. If I have this same problem, I will take it to a machine shop. no more drilling for me. It was a good idea but it hinged on one critical fact. You have to get the angle just right or it will not work.

Stuck
 

Howdy folks,
This is the nitty gritty on what is included in the MB repair kit.

ENGINES 601, 602, 603, 604, 605, 606, 611, 612, 613, 628, 646
REPAIR KIT FOR GLOW PLUG THREADS IN CYLINDER HEAD
A repair kit for damaged glow plug threads and/or broken off glow plugs in the cylinder head has been
developed. This repair kit allows for the drilling-out of the glow plug bore and the installation of threaded
inserts. As a result, the replacement of the cylinder head due to broken glow plugs (as an example) is no longer required.
The repair kit can be ordered as a Special Tool: 611 589 00 99 00.
In addition, the wear and tear components of the kit can be individually ordered as needed, along with
additional replacement threaded inserts.

Special Tool Glow Plug Repair Kit (complete kit) 611 589 00 99 00

The following replacement (wear and tear) items can be individually ordered:
Drill Bit, 8mm 611 589 00 99 03
Stop, 8mm Drill (used with 611 589 00 99 03) 611 589 00 99 04
Drill Bit, 5mm 611 589 00 99 07
Stop, 5mm Drill (used with 611 589 00 99 07) 611 589 00 99 08
Tap, M6 611 589 00 99 10
Stop, M6 Tap 611 589 00 99 11
Impact Adapter (M6 - M12) 611 589 00 99 13
Drill Bit, 3.5mm 611 589 00 99 15
Stop, 3.5mm Drill (used with 611 589 00 99 15) 611 589 00 99 16
Tap, M4 611 589 00 99 18
Stop, M4 Tap (used with 611 589 00 99 18) 611 589 00 99 19
Impact Adapter (M4 – M12) 611 589 00 99 21
Thread Cutter 611 589 00 99 22
Thread Awl 611 589 00 99 23
Thread Tap 611 589 00 99 24
Inserts, M10 (M10 x 1); (10 pcs.) 611 589 00 99 25
Wire Brush 611 589 00 99 27

The WIS document number for the detailed repair directions is
AR15.20-P-4112A for CDI engines.
So go grease up the palms of your local dealer's service manager or shop foreman, and thay can print these for you.

The glow plugs I have had to drill out or pull heads for have usually:
1. Melted, drooping into prechamber. Due to glow relay / afterglow failure.
2. Carbon, builds up around tip. Acts like cement. Most common.
3. Electrolosis. Happens with 606/611/648 glow plugs for some reason.

If your 210 diesel eats glow plugs, please make sure the afterglow feature
isn't sticking on. Check for 12v at glow plugs. Start car cold(<20 deg.)
Max on time for glow plugs after starting is 180 seconds. 12v should go away at 180sec or less. If not, like 5-10 minutes. You have failure of relay.

There is a tap/slide hammer adaptor for slide hammering out stuck plugs.
however, if the plug is melted into the pre-chamber. The head will need to
be removed so the center of the prechamber can be drilled out to access the mangled glow plug and cut/drill/blast out of head so the prechamber can be removed and head checked for damage.
Hope this helps a little.

Dr.Diesel

How does the insert work? It is M10 X 1.0 while the GP is M12 X 1.25?

The insert is for the smaller CDI 611-648 diesels which have 10x1 thread
plugs. When using this kit, I have just carefully drilled out the plug and cleaned up the m12x1.25 threads in the head to reuse. I have yet had to use a m12x1.25 heli-coil. Knock on wood.
The glow plug has always come out when the 8mm drill bit gets a bite on the
broken heater plug stuck in the prechamber. I have had lots of help from a penetrating lube called PB Blaster.
I am not aware of a factory insert for the 12x1.25 glow plugs, but I will call
my service tool engineering rep tomorrow for some answers.
Sorry to hear about your epic struggle.
These heads come off very fast. I had the head off this 99 turbo in less
than 2 hours. So if I feel that things may go south for me with driling.
I just pull the head. Better than a broken Cobalt bit stuck in the head.
Dr.D

Head is on the car and it starts. Thankfully I didn't need a new head as they are $1700 bare. Had to prime the hell out of the system. Finally it caught but the #5 cylinder would not work. After it ran, we let it idle and it seemed better. Looks like there was plenty of air in the fuel lines. All seems well. Will clean up garage and go for a good drive tomorrow and see what happens.