Broken Glow Plug Removal
 

I just went thru the dreaded Broken Glow Plug experience and I am here to tell you you CAN come out the other side. It started as a rebuild on the injector pump delivery valves (replaced O rings and copper seals). I figured I would replace all hoses, the shut off valve and glow plugs while in there. I have a '98 E300DT with 155K. Glow plugs last replaced at 90K. No light on and live in the Carolina's but now was a good time to get it done. All went well thanks to Lightmans post and then I ran into stubborn #5. It sat soaked in Creep overnite, heated with a heat gun. Eventually you just have to reef on it and of course it snapped above the threads spinning around on the electrode. Many thanks to Len (Sokoloff), Alan Reynolds and Dick for providing very good info and a PLAN.

I used a slide hammer attached to a #10 vise grips to remove the top (hex) of the glow plug. What remained was the electrode center. I then twisted the center (with Vice grips) in an attempt to snap off this center and give me a good center hole. I had dissected a glow plug and found that the center measured 1/4 almost exactly (Bosch). also found that the electrode was fused only at the bottom. That worked well and I had a good center hole to tap. First though I worked thru a sequence of bits moving eventually to 13/32to drill out the threads (mark your bit with duct tap as not to go deeper than the threads). I then used a 7mm tap and threaded the center to take a bolt. It doesn't matter what specific size you use since you supply both the tap and the nut/bolt. I went back and forth between a slide hammer (with a bolt welded on - see pic) and the 'bolt,washer puller' that Alan describes. Assemble the puller and start at it. Initially, when you first move the plug you will hear a crack and you are breaking the neck between the threads you drilled and the body of the plug. A Ratcheting Combo wrench here is indispensible. Eventually it really got stubborn when it was sticking out about an inch. The 7mm grade 5 could not take the torque and I went thru about 5 of these as they would gall, crossthread and sieze. Tapped up to a 8mm and this eventually 'dragged' it out (see pic). As the plug moves out of the head you will have to slip a socket over the puller to allow the glow plug to move into the hollow body of the socket. I used a 3/8 inch deep 14mm socket. All of the other plugs showed evidence of anti-sieze coating on the body of the plug. This one did not and it was covered in carbon. I stuffed grease covered tissue about a third a the way down the now empty plug hole and rethreaded with a 12x1.25 (common in stock for Mac, Matco, Snap-on but not in most of the sets -around $10.00), reach down with some forceps and pull the greasy wad out of the hole. The threadings will stick to the grease. I cleaned it out good with greasy Qtips and then reamed the hole with the glow plug tool. Since the glow plugs seat at the shoulder of the tip they only need 27nm (Thanks for this info Alan). I priced a Helicoil kit and found it readily available and priced at $80, luckily I didn't need to go this route. I coated the body of each plug with a liberal but not thick, even coat of nickel formulated anti-sieze, also put a film on the threads. I reassembled all and have some additional notes:

-I first used Kerosene and then Drive up - a driveway cleaner to clean my intake - worked great.
-I used bungee cords to move the injector lines out of the way during the Injector delivery valve rebuild.
-I tried the multispline extractor 1st on the broken glowplug - waste of time plus you are 'driving' against the soft alluminum of the head. - go easy. Insanity is trying the longer fluted type of extractor on this - do not do!
-as I drilled the threads out, I check the debris with a magnet for peace of mind, go slow, use a sharp bit, and tapping fluid.
-since I emptied all of my fuel lines and replaced the shut off valve I knew starting the car would be tough - crack open the main filter and top off with clean diesel. Use a mason jar that went thru the dishwaser and a CLEAN funnel, slide the filter forward till it bumps against the radiator hose and fill. I did this 2x and then the car FIRED UP!!!

Costs:

> I bought all lines, shut off valve, intake manifold gasket, spare spring, copper seals, O rings, spare fuel line shims (didn't need) and plastic fuel line keepers from my local dealer for $210 - not bad considering that the shut-off valve is around $140.
>I sourced the reamer, multi-spline socket (delivery valves) and the 14 crowsfoot for the fuel lines at Baum for $100.
>The plugs (6) cost me 137.00 on line - Bosch
>The 12x1.25 tap cost me $10 off the Matco truck

everything else I had on hand. I didn't come across the 'impact wrench burp method' until after I had snapped off #5. It certainly is counter intuitive but makes sense. I might try it next time. Considering that these break off on MB techs regularly I am pleased with the way everything turned out. RR on the head, rebuilding the delivery valves, replacing the glow plugs, fuel line RR and the shut off valve - I figure I saved thousands. It took me around 12 hrs off and on over several days. I work slow but methodical, always a good approach I figure when aiming a drill bit at an Aluminum head.

This is a great site; lots good people with a sense of community around a shared passion that is Mercedes-Benz. Thanks for the help!

Bill

Thanks for sharing the details of your innovative approach to removal. Another one to file away in the back of our heads...or better yet it might be worth summarizing and documenting these techniques in the DIY section.

Great job Bill - glad it all worked out.

Well now you need to go out and update your signature, as this is a badge of honor that is placed upon thee.

So, welcome to the ShopForm! Just spent a week in Charlotte, NC with way to much extra time on my hands, would have been just the entertainment I needed.

Good stuff, Sokoloff.

excellent
 

Way to go. Coincidentally, I heard a story about a MD mechanic who has become quite proficient at removing gp from the 606. I don't have the whole story, but it goes like this...
Remove the injectors, fill the cylinder with diesel, let sit overnight, vac out diesel, reinstall injector, drive until operating temp reached, remove gp like normal. Not saying anything but that I've heard this story and the mechanic charges $1200 for the job.

what about if you take a chunk of dry ice, or even if you can get it liquid nitrogen, and cool off the glow plug to extreme cold, combine that with a warm block and the gp might shrink enough to crack that carbon seal. if I ever need to remove one of these Ill try that.

I have posted before that it seems that an impact tool would be perfect for this. Using one of those cordless drills with the screwdriver settings would probably be ideal as they don't develop a lot of torque but that rap-rap-rap of the impact would probably free them up succesfully too.

I woukldnt trust an impact tool. Im pretty sure the torque is quite high, even if it is in pulses. I know ive broken off countless deck screws using a small dewalt cordless impact wrench.

The dry ice method you mention is more easily accompished using a product such as Freeze in a can. That combined with the rat-a-tat-tat of a drill or impact wrench on a low setting has much merit in my opinion.

My MB techs are going to work on my 606 for the head gasket. I'm hearing with the plugs you have to heat the engine well before you start. They want to remove them before they remove the head. Are any of you doing that?

Also would like to know if anyone knows who the OEM supplier is for head bolts. I found a good deal for Reinz bolts and would like to know that they are acceptable. My guys say to go to Mercedes but why pay the price if you don't have to. Also they feel you can reuse them as long as they "measure" up.

Hello, I will be attempting this job next week. I have a recently purchased 99 e300td. I don't have a record of when or if ever the gp were replaced. I just got the check engine light with a p0380 code. Car has 116k miles. Wish me luck

Before I'd jump into a glow plug replacement, I'd suggest you check the resistance on each plug with an ohm meter. Good plugs will read about 0.7 ohms. There have been cases of that code coming up and the problem was the glow plug relay and not the plugs.

If you do the glow plugs remember - hot engine, hot engine, hot engine.

I've changed glow plugs on my '98 e300 twice. You probably already have this, but in case you don't, these are the most helpful instructions I found:

PeachPartsWiki: LightMan's Step by Step Glowplug change

Len Sokoloff recommends a medium length Snap On 12mm socket; its number is Snap-on 12 fsm12. I bought one for the second time I changed them. It works better than other sockets I've used and costs $22 or $23 on line.

I did test them and #1 gp is bad. Thanks for the advice and reminder of the hot engine. :)

Thanks for the feedback. That is a great write up.

+1 it's actually Snap-On FSMS12 12mm 6 point 3/8" drive SEMI DEEP Socket. It does make a difference - thanks for tip. I just did my GP for the 2nd time. Nickel Antisieze made a huge difference. No problems. I did soak them for 48 hrs in Kroil. Last time I did this: 2007 with 155k - 12+ yrs. and 125k miles later.

Bill