'95 E300D - Fully Unthreaded But Stuck Glow Plug
 

I'm removing the glow plugs from my 606 engine. Three of them, 3, 4 and 6 were removed easily, as if they had been installed yesterday. Nos. 1, 2 and 5 are being difficult.

I'm working on #2 now. It appears to be fully unscrewed from the threads, but it is still difficult to turn and won't slide out. Is it possible that there is some corrosion on the shaft below the threads that is making it difficult to withdraw? The others looked fairly clean, although one was a non-functioning plug.

Anyone deal with this issue before? Any suggestions for how to resolve this?

Regards,
Tom

This problem can be due to an accumulation of carbon on the end of the glow plug due to an over-active EGR valve. My '96 E300D (same engine) had one glow plug that was a little sticky but eventually came out. After disabling the EGR valve (for testing) I have not had any more problems.
As far as removing your glow plug, there are "split nuts" that you can buy and apply to the glow plug threads; this acts as if the head is even thicker and gives greater purchase in gradually pulling the glow plug out. There are probably other tools that accomplish the same thing. In any case, gentle wiggling (squirt penetrating oil in to soften the carbon) works better than hard yanking, which might break the glow plug.

Jeremy

It is possible the tip is slighly swollen. The one in the first pic is exagerated. It does not take much swelling to make a plug hard to get out.

Keep pulling, turning and spraying. It will eventually ease out.

Indeed, Engatwork's suggestion above was exactly the process I used successfully. Literally just got the last of the three stubborn glow plugs removed. Once I was able to turn the plug, I just kept at it, back and forth by degrees initially, then more pronounced as it began to move a little freer. Each of the three plugs continually chattered and popped loudly as they were turned and didn't move freely until the very end.

A couple of thoughts, now that this fraught procedure is over, from a Mercedes and diesel newbie, so take this lengthy recap for what it's worth. First is that the glow plugs were stuck because of a buildup of carbon and tar on the shaft that extends below the threads--not due to the tip or corrosion seizing the threads. The tips were all straight, though some showed a little buildup of carbon. This accumulation on the metal shell, not the heating tube, made it difficult to withdraw the plug since it was in contact with the carbon on the sides of the pre-chamber. Even when the plug was turning relatively fairly freely, there was enough friction so that it could not be withdrawn, even with vice grips. See photo of plug. This vehicle just turned 135K, and there was no indication of the plugs ever having been replaced, so that's not surprising.

Once the plug was entirely unthreaded from the head but still unwilling to be withdrawn, I sprayed copious amounts of 2+2, a carb cleaner that works on carbon, around the threaded hole and just continued to turn the plug back and forth. This was a drawn-out process that took probably five hours for the three plugs. One plug eventually backed itself out as if it were threaded all the way to the heating tube. The other two weren't so cooperative.

With the plug rotating relatively freely and without the scary noises, I got a screwdriver under the hexagonal shoulder above the threads and levered on it while turning the ratchet. This eventually allowed to the plug to be extracted slowly, along with frequent sprays of 2+2. The damage to the threads in the glow plug picture was caused by the levering action of the driver.

What made this removal somewhat easier was the use of a Snap-on socket, FSMS12. This is a stubby, semi-deep socket a tad over 1.5 inches long. With my normal-sized deep socket, the ratchet would require several extensions to get it past the metal hoses, vacuum lines and wires to give it some room to turn. The Snap-on socket was short enough so that I could get a 3/8" breaker bar on the end of it and fit it between the metal fuel lines and other fittings. See photo. This gave me a surer control of the breaker bar than with a long extension and also eliminated the possibility of losing control of it and breaking something else. The socket was short enough to allow me to fit it over all of the glow plugs without removing anything. It also allowed me to slip it from the plug shoulder and move it to a new gripping point without pulling it totally off the plug.

Now to buy a reamer and some anti-seize compound and do the installation of the new plugs. A satisfying end to a somewhat nerve-wracking DIY project. Then, onward to the engine harness replacement.

Regards,
Tom

There is not supposed to be carbon building up between the threads and the heater element. I used your pic and the red arrows point to the shoulder that the Glow Plug is supposed to seal on.
The Glow Plug reamer does not clean the sealing area that the shoulder contacts so it would be a good idea to get a flashlight and peer inside of the hole and see if there is no carbon on that sealing area.
I am not sure what people use to clean that.

I enlarged the threaded part of your pic. If the area circled in yellow has aluminum stuck to it (I cannot tell from the pic if it is aluminum or not) that would be the area where the plug coroded to the head.

You might experiment by blocking the EGR valve so it no longer dumps carbon into the intake manifold. Try it for, say, five or ten years, see if it makes a difference.

This diagram is of an older engine but the glow plugs seal the same way on them. The red line indicates the shoulder where the glow Plug seals/seats. Only the heating element is supposed to be exposed to combustion (which would cause the carbon).

I have read a lot of threads on these 60X engines with the stuck GP`s.
I do not have one of these newer engines as mine are the 61X engines.

I wonder if these plugs were removed say just before each winter to ream out the holes,
clean off the plugs and add new Aiti-Seiz compound, if it would eliviate this problem?

I know with the average owner, whether MB, Ford, Honda or what ever....
once the hood is slammed shut....outa sight, out of mind.
That is till there is a problem.

Not pointing fingers here at anyone, just thinking out loud.
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Charlie, the problem is the DOHC configuration requiring a long, thin glow plug. This gives lots of room for carbon to build up and not much steel to resist the twisting forces of Mr. Armstrong. Result=snapped glow plug. A disabled EGR system is the best fix but your suggestion would also reduce the problem.

Jeremy

As I noted in my post, those marks were from the screwdriver where I levered it into the side of the glow plug to assist in its removal. None of the plugs exhibited any problems with corrosion of the threads.

My conclusion was based on the fact even after the plug was unthreaded completely from the seat so that damaged threads would no longer be an issue, it refused to slide out, and remained very difficult to turn with the breaker bar, popping and snapping as it was moved. An examination of the plug showed an uneven buildup of carbon on the body of the shaft above the heating end and below the threads that could be felt by running a finger over it. In removing one of the stuck plugs, it finally backed out as if it were threaded down to the tip, indicating to me that the carbon might have been thick enough to be caught by the threads in the head. None of the plugs were totally clean, but the ones that were stuck showed much more carbon in this area that the three that came out easily.

In addition, the two tightest plugs, including the one that I pictured, refused, after removal, to slide back into their bores far enough to start threading, indicating interference in the prechamber below the threads in the head.

Finally, once the plugs had cleared the threads a bit, pumping 2+2 down the bores seemed to quickly free it up enough to have it turn easily, tho still needing to be levered out.

Can't say this is the case with all 606 engines, but certainly in this individual instance, neither corroded threads nor bent heating tip appeared to be the cause of the removal problems.

Regards,
Tom

Someone mentioned a while back that a reamer is included with the on-board tool kit.

I must admit, both of my kits have a glow plug sized piece of aluminium but unsure if this correct or not.

Far right pocket

http://www.benzworld.org/forums/atta...t-dscf1816.jpg

Well done OBG! Some additional info below but somehow I think you know all this anyways.

http://www.peachparts.com/shopforum/diesel-discussion/376521-om606-glow-plug-removal-tips-tricks-2.html

A closer look at this pic tells me this glow plug was either not torqued properly or the seat in the head had debris on it, allowing a breach of combustion gas/ carbon to go past the seat and jam the glow plug body against the bore in the head. I doubt these are the original glow plugs from the factory since you said 3 of them are like this.

http://www.peachparts.com/shopforum/...removal-1-.jpg

I saw this video last week, it's quite relevant:

https://www.youtube.com/watch?v=U9AO_cDdwS8&index=2&list=LLbjGpxeoF8uEbPzYTMiGd1g

-J

That's a pin to help you get the wheel seated on the hub. It screws in place of a lug bolt. It's much bigger than a glow plug.

-J

That solves that mystery, thanks - useful too, will give that a go next time wheel swapping.

Yes, I had read Maxbumpo's description of the removal of his glow plugs earlier this year--in fact, I had printed out his description and had it taped up over my workbench and used his list of tools and parts as preparation for my own attempt.

What I hadn't done was read the second page of the topic carefully. I note now that Eswhwab had mentioned seeing a recommendation for the same Snap-on socket I listed.

Funola's posting there regarding the failure of the plug to seat properly as cause of the buildup of carbon and tar on the shaft of the glow plug makes perfect sense and I will have to make sure that I get the seats clean, ensure they are undamaged, and torque the plugs correctly. I also agree with his assessment that, with proper seating, the plugs should be able to be removed easily, which is what I found on my engine for the three plugs that showed absolutely no carbon buildup on the body. As I said in my original note, it was as if they had been installed yesterday. I will probably coat the entire glow plug shaft from threads to seating area with high-temp anti-seize.

One thing I did not note in my description was that I had plugged in my block heater (the internal one at the back of the engine on the passenger side) and had let the engine warm up before trying to remove the plugs. I left it plugged in during the entire process. Engine temp gauge showed just under 60C--assuming that's the line on the gauge between 40 and 80 degrees--and the engine was quite warm to the touch. Also, knowing the precarious condition of the wiring harness, I did not touch the wiring except to disconnect the glow plugs.

Thanks to everyone for their suggestions, recommendations and comments! I'll post again when I get everything back together and the engine started so I can finally exhale. I need to round up a number of parts before I can complete it. Still looking for the engine wiring harness, but no longer doing it optimistically...

Regards,
Tom
Closter, NJ

Carbon is not supposed to get past the sealing shoulder on the Glow Plug EGR or not.

My best guess is that either the Glow Plugs were not tight enough to seal or there is some issue like warping of the aluminum that broke the seal. That is assuming the head had no defect when it was made.

On three prechambers with interference issues, I was going to try a stiff wire brush with a frequent shots of the carb cleaner before the reamer for the tip. I looked down the bores with a flashlight, but couldn't really see anything. I'm going to try to find a small light that might fit into the bore or, perhaps, a friend with one of those mini cameras on a stalk designed for just this sort of inspection.

The glow plugs themselves did not seem to show any damage at their mating face with the head, but that's not to say there isn't some damage down there. My guess is that that they weren't tightened down enough, which would be ironic since the glow plugs that are difficult to get at were fine--some good luck for a change.

Regards,
Tom
Closter, NJ

Ran into this same "stuck" gp myself on the OM606.912 in our '96 E300.

I recently replaced all the glow plugs on this engine. I bought the Hazet reamer and used Bosch glow plugs which I torqued to spec. Today I pulled the intake and removed the injectors to have them serviced and I noticed that the high temp anti-seize I used on the #3 glow plug appears to be blown out of the hole. Seems there is a compression leak on this one. This particular GP was a PITA to remove when I replaced them, while all the others were easy.

Thank you Compu_85 for posting the link to that video of the British chap removing and installing glow plugs in the OM606. I'm going to use drill bits to clean out the bore and the seat per his suggestion. We'll see how it works.

I came up with a solution for cleaning carbon off the sealing seat where the glow plugs seal right behind the tip. I didn't like the idea of using a drill bit for a couple reasons. The angle of the bit's cutting edges would not match that of the sealing seat, and the drill bit would likely remove some material from the head in the process of using it.

I made a tool out of a dead glow plug. Using a glow plug to make the tool has two advantages. The angle of the old plug's seat matches the angle in the head, and the finished tool would not have any risk of actually cutting into the head's material, unless pressed really hard against the seat.

First I cut the tip off leaving just a little protruding from the outer shell of the glow plug. I then cut two notches into the sealing seat using a cut-off wheel mounted to a Dremel, angled back a little to create a cutting/scooping edge. I used a wire wheel mounted to a bench grinder to clean off the burrs raised up by the grinding, to leave clean working edges. I also ground off the threads so the tool could be inserted all the way to making contact with the seat, and then rotated while in there.

After running the Hazet tip reamer through and using a wire brush to clean out the hole between the tip and threads, I then inserted my home made tool and used a socket on an extension to press the tool into the seat and rotate by hand. I used a deep well socket that I shortened so it would not bottom out on the head, allowing me to press and turn the cleaning tool at the same time. I did this three, maybe four times, pulling the tool out, clearing carbon from the notches in between goes, until the tool came clean.

Sure enough, I managed to remove a fair amount of carbon from the seat that was left behind after the previous reaming and wire brushing. I was able to shine some light down the hole and I could see the nicely cleaned seat down in there.

Hope this idea helps someone else!

That's excellent thank you for sharing,

That tool screws into a wheel bolt hole and is used as a guide when replacing wheels. It keeps the wheel on the hub while you reach down for a handful of bolts.

'95 E300D - Fully Unthreaded But Stuck Glow Plug
 

Well, just finished bolting the last bit back on the 606 tonight and the long glow plug adventure is over, at least for now. Not a difficult job and well within the capability of a minimally experienced DIY-er since I was successful in completing it! I do have a question. Actually two.


When I started the engine after reassembly, the glow plug light on the dash board came on as it should, but stayed lit for only four or five seconds. The car had been sitting in a 65F garage all day. Is the glow plug bulb cycle time controlled by the internal temperature of the engine or the external air temperature? Seemed to turn off very quick, tho it was warm. I don't recall what it had done previously since for the past couple of months I didn't get the light until after the car started.


Despite some assiduous searching, I had no luck in tracking down a later glow plug wiring harness--the search was one of the reasons the job took so long since I was loath to reassemble if I had to undo it all again relatively soon. So I'm in the market for a used harness. It can be the early variety with the part number ending in 3932. I'm going to have to have the harness recreated and I'd like to have a loom I can provide to whomever does the job so I don't need to lose the use of the car for any length of time. If anyone has one for sale, please let me know.


As I was cleaning up this evening, I tested the old glow plugs with a 12V ready pack. Five of them lit up readily and glowed brightly, one didn't. With 135K on the car, I'm happy to put the new ones in since I don't know when these were changed last--and the whole issue of snapping them on removal was avoided. Is there some other way to test these to see if they are reasonably good enough to use as spares?


Thanks to all who offered advice and suggestions to me. Much appreciated!


Regards,
Tom
Closter NJ

You glow lamp is behaving correctly. When it comes on after not during a glow cycle that indicates a failed GP. The time of glow is based on a water jacket temperature. Can't help with the wiring harness but they do show up on ebay every so often. The tips of the GPs should glow then they are good.

That brings up another question I had when my glow plug problem first started. Although the glow plug light doesn't come on until after the engine fires, I wondered whether the good glow plugs light up during the normal pre-start sequence? Or do they light up after the engine starts when the dash light is on? Or do they all not work when one or more are bad?

Regards,
Tom

Fully operating system - once key is in position 1 glow lamp turns on once it goes out you are good to start.

This is where I'm trying to rember a flashing lamp indicates a fault during the wait time. If the lamp goes on after a start that indicates a short circuit the relays have an automatically resettable circuit breaker.

When the Key is in the pre-glow position the Glow Plugs will remain on until the timer shuts them off or you turn the Key to start (as an example because you watched the glow Plug light and it went off).


How long the light and maybe the timer stay on is determined by the temp sensor.


While you are cranking the Engine the Glow Plugs are on as there is a Jumper Wire connected to one of the Starter Terminals that keeps them on.


I don't know if your year and model has the after glow feature. So someone else can post on that.


The reason your glow plugs are on during cranking is that the Glow Plugs in cold weather get hotter then the heat of compression could do in cold conditions.

Gmog....can you share what Hazet part number the glow plug reamer is?
Thanks!

The Hazet reamer is a newer tool but the older style one is cheaper and dies the same job. People have also used other methods which are in the repair links.

Repair Links Fast navigation http://www.peachparts.com/shopforum/diy-links-parts-category/146034-fast-navigation-do-yourself-links.html

The long one at the top in the first pic would work on a 1995.

The 2nd pic shows the Hazet reamers with the one being the one that would work on your 1995. The Hazet Part Numbers are etched on the smooth part of the reamer body.

The reamer I bought is 4798-3. My engine is OM606.912. Matches the top reamer in the photo of Hazet reamers provided by Diesel911. Sourced it from the Pelican.