Hi Guys,

I searched the forum before posting a new thread. I couldn't find the right solution for the problem I am having, so any advice would be appreciated.

I purchased a 94 S350 not long ago with #18 cylinder head, the car is in running condition with quite a few problems. One of the problem is really hard to start. I was told that the glow plugs might be bad. Since the car has zero maintenance record, I thought that would be where I start.

After removing the things block the way, I was able to access the glow plugs. but I had something unexpected. I measured resistance on all plugs, one is about 20 ohm, others are way over 200 ohm. So I believe they all need to be replaced. Out of 6 plugs, I was only able to replace two without issue, the rest of four, had black stuff around them, I don't know what it is, looks like some sort of paint, or dried tar, definitely not carbon deposit because it is kind of shinny. After cleaning the black stuff around the plug, I started removing the first plug near the grill. The plug was really tight, I had to use a lever to break it loose, it turns now but it won't come out no matter what. I thought I may break the plug into two piece, but at least the outer piece with the threads should come out, right? How to take this plug out now? Did I mess up the threads, or crack the head? I am running out of idea now, any suggestions are greatly appreciated.

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This is what I've always done. Run a sheet metal screw with a beveled hex head in as far as it will go and when it start to turn the plug. Then, close the jaws of an adjustable wrench around it toward the engine. Then start to lever stuff in there and try to lever it out as you turn it with a 1/4" drive ratchet with a socket on the head of the machine screw, take your time. It has never failed me on many different makes and models. It will squeak on the carbon as you remove it. Run a reamer in there afterward.

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I'm glad you had luck with a screw in the plug end... I would NOT recommend this to anyone though. the possibility of expanding the plug, and PERMANENTLY damaging the head is a pretty pricy mistake.

there are special tools designed explicitly for the task of removing stuck glow plugs.

the 603 is not normally associated with stuck plugs though.

I'd soak the plug in AEROKROIL or PB Blaster for a few days, and try again.

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When you get the stuck tip out of the Head run a Glow Plug Reamer through the Head to clear out the Carbon.
Should be info in that:
DIY Repair Links
DIY Links by Parts Category - PeachParts Mercedes ShopForum

PeachPartsWiki: Do It Yourself Articles - Mercedes Vehicles

Use only Bosch or Beru Glow Plugs to replace the bad ones.

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84 300D, 82 Volvo 244Gl Diesel

Burned Oil can end up that shiny tary black color.

Carbon is likely trapping the Glow Plug Tip in the area with the Red Rectangle in the pic.

Repeated applications of the Chemicals mentioned in a previous Post would help to soften and lube the Carbon that is holding the tip in.

You also might want to pull the Injector and look at the tip. Some Brands of Glow Plugs have been known to have the tips swell up.

Or worn out Injector Nozzles can cause Fuel to spray on the Glow Plugs and burn and deform the tips.

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84 300D, 82 Volvo 244Gl Diesel

Did the gp back out at all? What you are describing is not a broken tip. If its backed out the threads and is stuck then a good soaking should do the job.

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Thank you all for the replies. I think I didn't make myself clear, I cannot take the glow plug out at all. It will turn with the socket, but it won't come out any further, it stays in the hole as shown in the picture. I tried to pull with a pliers, hoped at least outer part will come out if I broke it, but it didn't. I did buy new Bosch plugs and a reamer, but at this point, I have to figure out how to take old ones out without cracking the head, or messing up the thread. I found some videos on youtube, it seem that in order to use those special tools to take the plug out, I have to remove the head?

Thanks again!

Hi Diesel911,

Thank you for the link. I think I have to take the head out to do this whole drilling thing, the direction of the GP on om603 makes it impossible to drill while the head is on the engine......

Is it turning and just stuck or broke? If turning but not broke try removing it with the engine running. I typically will remove the harder ones with the engine running. Just have to be careful when it first breaks loose.

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Jim

GP should not get stuck in the OM603 head. How many GP turns but cannot be pulled from the head? A lot of the time it is the carbon deposit ( or the GP got fattened by usage ) on the GP that stops it from coming out. This is what I normally do. I put a 11mm open ended spanner behind the plug. If you have threaded it all out then the spanner should be able to go behind it. Put a big screw driver behind the spanner and turn or use the spanner as a lever. The GP will come out. I doubt there is anything in there that could damage the head. You can also remove the injector and look inside the pre-chamber to see what is blocking the GP hole.

Good luck.

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This sounds like only the Tip is trapped in the Head and the threaded part of the Glow Plug and the hex head are intact. It simply has backed out of the head past the threads on the Glow Plug. You generally do not need to drill them out when the Tip is trapped like that.

The Drill out is needed when the Hex Head snaps entirly off of the Glow Plug and leaves the threade part of the Glow Plug still inside of the Engine.

You need to be patient and give time for something to soften up the Carbon.

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84 300D, 82 Volvo 244Gl Diesel

Hope it is like you said, I didn't have a chance to work on the car yesterday. Will compare with other plugs to see if the threaded part has come out all the way. Soaking is mush easier than taking the head off. Thanks!

I was able the change the plug on cylinder #2 and #4 (assume #1 is the closest to grill). #1 is stuck, I haven't touch the rest. Just curious, how do I check pre-chamber without removing the GP? Thanks!

#1 is closest to grill. If you remove the injector then you can see the tip ( about 1/2" ) of the GP. The GP is sitting beneath the injector. The GP probably is burnt out and swallon, i.e. too fat to get thru the head's hole. You may be abut to put a magnet thru the injector hole to catch any big pieces broke off when you yank the GP out. I would not worry about any loose bits as they will burn out eventually in the chamber. There is nothing that can stop the GP from coming out. Good luck.

see picture on first post

MONARK vs. BOSCH INJECTORS

__________________
Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

Somehow I was thinking about the injector pump instead of injector when I see your thread, I don't know why . After seeing the picture, it makes sense now Thank you.