Removing Glow Plugs With Wax
 

Just wondering if anyone here ever attempted heating the aluminum head around a stuck glow plug with a torch then apply candle wax rather than pb blaster or some other penetrant.
I have used this method in the past with success on seized bolts. the melted wax seems to "wick" into the threads similar to solder flux when soldering copper pipes.

Get the engine warmed up. Ok to run without the manifold to get it warm, use common sense and don't let anything get sucked in.

Try AeroKroil penetrant, nothing else compares.

I would get it warm, pull the manifold, and apply the penetrant in the evening (like Friday night). Then Saturday morning start it up again and let it get heated up. Then hit the plugs again with the AeroKroil.

Wait a few minutes then use a battery operated impact to free the plugs. I have read many threads on this and this seems to be the best tactic. Don't use a gorilla 3/4 inch air compressor impact, just a little 1/4 inch battery drill type with a socket adapter. The impact has several benefits. One is that the many small shocks are better at breaking the plug loose than the constant force provided when you turn the ratchet. Also applying force with a ratchet tends to be off center due to the physics involved, this ends up applying an uneven force to the plug and I suspect this is what really ends up snapping them off.

Also don't forget to pick up a tube of Anti-Seize for the new plugs. And be sure you have either the official reamer tool or use an appropriately sized drill bit smeared with grease. Use No Power Tools on the reamer!!

Excellent advice Jay-Bob,
I just bought this car with all service records from previous owner and came across one of the invoices from 2012 that stated #1 glow plug was replaced and the remaining 5 were seized and not replaced at owners request. I called the Mercedes service center that has maintained this car and the guy I talked to was very familiar with it, he said previous owner was very very meticulous with the car but opted not to spend the money to change the glow plugs because the car was stored winters. he also told me what they do is set a torque wrench to the correct value for glow plugs and attempt to remove the plugs and if they do not come out the head comes off and goes to a machine shop were they get cut out with an EDM machine, then the new plugs go in and the head goes back on and $4000 later you are good to go!!

You are the first one that has posted that it works.

I am inclined to think it would work where the treads are corroded but not if they are siezed due to Carbon leaking past the sealing area (the plugs don't seal on the threads).

Note use some never-sieze type compound at least on the threads of the new Glow Plugs to prvent the corrosion.

Well gee, I was a mechanic for 18 years and never had any one say melted wax would help loosen nuts and bolts! Not even the old timers.

One of the reasons I read this forum is to learn new stuff and today I did.

"My favorite trick for removing rusted NPT pipe plugs from cast iron is to heat the surrounding iron, then melt a candle on the threads. Paraffin will wick into the threads and act as a lubricant. Be sure to use a snug fitting, proper sized socket. In this example I used a special female square drive socket that fits the square on the pipe plug."

"Be sure to first clean off all the penetrating oil and only use open flame in areas
safe to do so. ... iron is to heat the surrounding iron, then melt a candle on the
threads. Paraffin will wick into the threads and act as a lubricant."
Removing Rusted Bolts

The Art of Removing Stuck Nuts and Bolts - DSPORT Magazine

Who has bees wax in their tool box ? [Archive] - The Garage Journal Board
"Recently I retired from going to sea for 30 years. I sailed deep sea as an engineer. Every ship had blocks of bees wax in the machine shop. It is for sale in the Mariner's Catalog.

Steam engineers, even before the Cival War, melted wax on hot stubborn nuts and bolts. It would seep into any thread or frozen up tight space. This was used way before Blaster and Liquid Wrench was invented.

I often heat up things gently and then put the wax to it. Some poor guy on a different thread was fighting a sheared off water pump housing bolt. I would have heated the bolt head with a small flame and let the wax do all the work."

I am afraid this old trick is not used very much anymore except by seaman that I've worked with. I have found it in a few old hardware stores and also on the internet. Everyone that works with tools should buy a block. :thumbup:

FYI, the union I was in was formed in 1876. A lot of the ship and riverboat engineers were also train drivers. Anyway I hope this bees wax trick helps somebody out, preferably before they shear off a bolt or stud.

+1 on 'its not the threads that seize' - been there done that. The carbon below the threads seizes the GP. The neck snaps off below the threaded body. Hence the strong advise to use Neverseize on the GP.

Another option to keep the engine warm while you work on it is to plug in the block heater. (Obviously this assumes your car has one and the required cord.) This is especially helpful if you're changing all the glow plugs and thus taking longer than just one.

Jeremy

I use this trick all the time. I think I learned it on the practical machinist forums, and first used it to get a frozen stud with over an inch of threads rusted into an iron block out of a ford explorer (worst car ever to work on).

Everything else failed on that bolt, but after two heat, add wax, cool cycles, it came right out. Best wrenching trick ever.

I was under the assumption that the threaded portion of the the glow plug was the area that becomes seized. Now that I have a better understanding of where the carbon is actually building up, that changes everything.
If I understand correctly there is a chamfer near the bottom of the glow plug body and the electrode protrudes beyond that approx. an inch or so.
The chamfer near the bottom of the glow plug body seats at the bottom of the pre chamber in the head where it has a chamfer at the bottom as well.
If the bottom of the glow plug is not seated at the chamfer, carbon will migrate and impact the length of the glow plug body up to the underside of the threaded portion.
If I am correct, this would be like trying to remove a bolt that is embedded in concrete!?

Yes it can either be corroded threads or carbon build up or both of them combined.

From the number of posts corroded threads seem to be the most frequent issue.

Aerokroil has been ordered and on it's way.
Thanks again for your help and wish me luck!

Best advice is right here and the method I used to remove the glow plugs on my now sold '98 E300. If they still don't wanna come out, tighten it with a ratchet and back it off again. Rinse, wash, repeat!

Next time I come across the issue (twice so far) going to try another theory by building small clay walls around each injector well. The idea being to fill with small amount of solvent (bio diesel) then drive a for a month or two.

What's the chances of it working through to carbon affected areas?

Assuming the OP has an OM606 engine, I would heartily recommend this approach, which will cost you some injector heat shields, probably a meter of the injector return line hose, and an oil change. Apply your penetrating oil INSIDE the pre-chamber to the carbon-bound end of the glow plugs. You'll need to make a hose with a bent tip to reach inside and around the corner to the base of the glow plug, I used a piece of old vacuum tubing heated with a hair dryer or a propane torch to soften and bend it.

Start with a HOT engine, drive it around for at least 15 minutes past the time when the coolant reaches normal operating temperature. Immediately plug in the block heater once parked, and remove the intake manifold, injection lines, and the injectors. Apply your penetrating oil to the outside of the glow plugs, and inside the pre-chambers to the base of the glow plug element, where the carbon packing is probably occurring.

Go very slow and easy with the torque on removing the plugs, stay below 45 Nm. Jake's tip is good, you may have to cycle between loosen / tighten to allow the oil to work its way in.

I LIKE the wax idea for the outside of the glow plug, there indeed may be galvanic corrosion between the steel plug body and the aluminum head. More heat is only going to help.

I am surprised I was never told about this because I used to work in a Diesel Shop at a Naval Shipyard for 6 years. Also the people that I worked with and been through an apprenticeship program and there were 2 machinist right in front of us in the same building.

Lots of the stuff we worked on was badly rusted.

Then just to the side of us there was a section that was part of the “Steam Gang” that worked on the stuff steam stuff for the Ships steam turbines. I mean 2 guys would spend 2-3 hours trying to remove the large Bolts with a Sludge Hammer and a Slug/Striking Wrench.. And there was 6 or more Bolts just on one side of the items they worked on. It was a daily struggle for them.

I once spoke with my Forman and said that if replacing the Bolts costs less then the labor to remove them they should cut the bolts off and buy new Bolts. But, I doubt if he ever looked in to that as it was not our shop.

So who knows if some Wax might have helped as they were there with Torches heating the stuff up. I know they used a lot of Penatrating Oil.

By the way that was Tax money going to pay those guys to beat off the Bolts.
　

If you look at the hot heater end of the Glow Plug right where it goes into the Glow Plug Body you will see an angled shoulder. That tapered angled shoulder is where the Glow Plug seals to the Cylinder head.

In order for Carbon to get past that the plug would have to be loose, some junk got between the plug and the seating area in the head when the plug was installed, the head was machined with a defect in the sealing area or what I believe is more likely the head warped enough break the seal.

I say warped because on the aluminum Cylinder Heads it is not uncommon for warpage to occur and the pre-combustion chamber looses the seal and the sealing area needs to be resurfaced with a cutter.

If the actual tip of the Glow Plug that protrudes into the precombustion Chamber gets carboned badly and stuck usually the Glow Plug will come out but the tip often comes out of the Glow Plug Body and stays in there.

That is what I have gotten from other peoples experiences.

Yup, agreed, it seems to be the whole shaft that creates the friction when trying to removing, almost as if the carbon dislodges wedging itself in between, perhaps warping is also an issue as you say.

Thinking about my theory above, might be a bit too fiddly, how about a ring of suitable fabric to sit over the plug, needs to safe from combustion?

The carbon packing is on the working end of the glow plug. A better approach would be to plug the holes in the bottom of the pre-chamber and then fill that up with penetrating oil.

That's a really interesting observation by Diesel regarding warping, on the plugs removed most were reasonably free of carbon and other build up, this could of course be due to the solvents used during removal.

Perhaps the narrow tubes which locate the plugs distort over time?

The only place there should normally be carbon is on the tip that stick into to the pre-combustion chamber and the hole in the head that the tip goes through which is past the sealing area gets carbon build up. There is a Glow Plug reamer to get the carbon out of that hole or there is alternative methods.
If you remove the Glow Plug you should clean the carbon out of the above hole.


I have never seen any tool on sale to go in and clean out past the sealing area outwards. Also none to re-cut the sealing area in the Cylinder Head.

jay_bob, I wanted to simulate removing a seized glow plug before attempting it on my car. I took a piece of aluminum, drilled a hole a little larger in diameter than the small end of the glow plug (the tip that glows) then drilled down with the tap drill staying above the bottom of the block for the glow plug to seat at the bottom and finally taped the top and removed all cutting oil.
Using an oxy acetylene torch adjusted with a yellow flame, I covered the glow plug with soot, then screwed it into the block as tight as possible without risk of breaking it (I do not have a torque wrench yet) then applied Aerokroil and let soak for three days. I put the block in a vise and hit it with a small 3/8" air operated "butterfly" impact wrench (80 ft/lbs. max.) turned way down. I turned the wrench up half way, I'm guessing 40ft/lbs. and the glow plug would not budge. I tried this several times letting the impact wrench hammer for at least ten seconds at a time. the next thing I did was to heat the block up with the torch getting it just hot enough where I could hold it in my hand without getting burned. I hit it with the impact wrench and the plug spun right out!
Your idea of keeping the engine warm is excellent advice.
I might try this test again with the block cold and turning up the impact wrench a little at a time just to find the breaking point of the glow plug then turn it back down somewhat when I attempt this on my car with the engine warm.

I like your experimental methods.

Make an effort to ream the glow plugs each year from the day of installation to avoid any issues with carbon and snapping glow plugs. My advice on the forum to everyone is an impact 3/8 on the lowest setting, block heater plugged in with a hot engine and pb blaster, and hammer the plugs 10 15 seconds at a time. Tighten, loosen, tighten. I did this twice so far and am going to attempt the method tomorrow on a customer's 99 e300. I've yet to have any heads have to be removed.

Please let me know how it goes for you tomorrow!

I think I'll try the wax.

> Penetrating oil . Average load .. Price per fluid ounce
> None .................. 516 pounds .
> WD-40 .............. 238 pounds ... $0.25
> PB Blaster ......... 214 pounds .. $0.35
> Liquid Wrench ... 127 pounds .. $0.21
> Kano Kroil ........ 106 pounds .. $0.75
> ATF-Acetone mix.. 53 pounds .. $0.10

> The ATF-Acetone mix was a 50/50 mix (1 to 1 ratio)."

I did it today and it took me a total of 3 hours to change the glow plugs and have everything back together. I wasn't in a huge hurry, but I used the method I mentioned and it went smooth as butter. 3rd attempt worked.

NICE, I will definitely use your method. looking through the stack of service records that came with my car I see the last attempt to remove the glow plugs was back in 2011.

Yes if you lived in the area, I'd be more than happy to help you and do it for you. These cars are trickier than my other diesels. The key is patience. Also, remember this trick has worked for me every time, but a glow plug always runs the risk of breaking. But this is the method I found works best. Take that into consideration, but it is slim chance. A dealer tech at MB was the one who taught me the trick

What's the torque on your 3/8 impact set on? Do you know that torque?

see what tool this guy uses to clean out above the sealing area.
https://www.youtube.com/watch?v=wHke1843zxo&t=17s

Thanks but I can't watch in till I get to the Library Computer my dial up is not up to it.

I know that bronze Gun Bore Brushes come in different sizes.

SHOTGUN BRUSH SIZES; threaded end 5/16x24 inches in the USA.
Diameter of the Brushes.
10 gauge 0.775"
12 gauge 0.729"
16 gauge 0.662"
20 gauge 0.615"
28 gauge 0.550"
410 bore 0.410"

But some people were scared a bristle might break off and get into the Engine. Even though Diesel Injector Tube Brushes are the norm on Trucks and I have never seen them cause an issue.

I wonder if it might be safer to rotate the brush using a battery operated drill rather than pushing it in and out of the hole?

OK I viewed the vid. Looks like a shotgun bore brush and an cleaning rod to me. For some reason the sound was not loud.
OK he said it was for a 50 cal BMG which is like the 50 cal used in the Machine gun.


But, his rig is not going to get into the hole that a Glow Plug Reamer takes care of as it 7mm and the 50 Cal brush is going to be 12+mm.

But, Carbon is not supposed to get beyond where the vid shows cleaning. You should only need to clean that if carbon has caked inside of there.

You are correct, carbon should not build up beyond the sealing surface of the glow plug, I just wanted you to see what tool could be used if carbon was to seep up the glow plug.
I will follow Jake12's advice on glow plug replacement, this guy has removed seized glow plugs three times now with success and he explains his method in detail including reaming the glow plug holes.
We can discuss our ideas and methods for this all day long but I will put my money on the guy with the experience every time. jake has been there, done that, and his method is proven. he also offered to help me with my glow plugs if we lived closer together...how cool is that?