Glow plug removal article

I am writing this article for a few reasons.
Firstly, because I was asked by a number of guys if there was a way to remove glow plugs so as to not break off the tips inside the engine. The short answer is No, there isn't any guarantees, . However, before you all feel like just walking away and selling your "baby" for scrap, there are a few things that you can do.
Secondly, since I was unlucky enough to have to go down this road and ended up having to pull both heads off my engine to retrieve broken off glow plug tips, I figure that even if I save one guy from having to do the same, then my time will be well worth it.
I have heard of all kinds of ways to remove the glow plugs, especially ones which are stuck. I've heard of guys just unthreading them and then starting the engine, and letting them "blow" out. Apparently this sounds a lot like a gun going off, and if you don't mind stripped thread holes, and a few holes in your hood that resemble bullet holes, then maybe this is the method for you(not me!). I have heard one guy claim that he filled his cylinder with water, and cranked the engine, and the water being forced out of the cylinder "blew" the plug out(not me!) I've also heard of guys who just crank on 'em and if they break off, then so be it, they just start 'er up, and hold the throttle at governor speed until the bits come out somewhere!! I suppose that could work, but one fellow sent me a pic which shows what can happen if you try this method. This is a pic of his removed oilpan after a glow plug tip failed to "pass". I was lucky, I only split one piston, and at least my engine was salvageable!!
What happens when you try to pass a glow plug tip!!
So, one has to understand what it actually looks like inside the heads where the glow plugs are positioned. It's really difficult to try to explain what/why these broken off tips become a problem, but I drew a diagram that I hope sort of helps others to "see" what the problem is. The glow plugs are mounted into an area of the heads called the "pre-cups" They are designed to help "swirl" the fuel air mix before it enters the cylinder and start the ignition of the mix. However, by their shape, if a glow plug tip breaks off, it becomes very hard to reach once it is inside the pre-cup chamber, and if it falls down into the cylinders, then it becomes even more difficult. So far, I have not heard of one viable solution to this problem,and I have not heard of one person who has come up with a way of getting these bits out of the engine other than pulling the heads off, or taking a chance on the kind of damage as seen in the previous photo, and starting it up. Have a look at the following pic(lousy artistry) and you'll see what I'm getting at....
pre-chamber approximation
You can see that if the broken off tips/bits make their way down into the cylinder, since the hole is only about 1/8" in diameter, there's no tool I know of that can go around the corners and down into the cylinder to retrieve these pieces, and somehow grab them and pull them back up. Remember, that this all has to be done from above, outside the engine, without any direct vision of what's going on.
here is the real pre-chamber as seen removed from the head. Note the glow plug size, and the tiny hole where it is mounted in the head. The other larger hole is where the injector tip is mounted. If you look closely, you can actually make out some tiny cracks developing in the pre-chamber insert surface itself.
pre-chamber, plug removed
pre-chamber, plug in place

Ok, so have I got you completely depressed yet? Well, I think I may have come up with something which may occasionally get someone out of trouble. It did work for me, but not until after I had dropped 2 glow plug tips(one in each side) into the cylinders and had no choice but to remove the heads to get them out. It may not work every time, and is not a guarantee, but like I said previously, as far as I'm concerned, even if it saves 1 guy from having to pull the head(s) off, then it was worth my time to write this.

Put simply, it is this. When the pistons are at the top of their travel(top dead center or t.d.c.) there is virtually no space in the cylinder where the glow plug tips can go. they can not drop down out of the pre-chamber into the cylinder bore.. Since the hole where the injector goes is quite a bit larger than the glow plug holes, I found that with a strong suction device( I used a powerful shop vac) attached to the injector hole it is possible to suck the tip up/out of the injector hole. A little compressed air blown into the glow-plug hole can also help to swirl air around and hopefully drive out the broken off tip, but one must be careful to prevent rotation of the engine using a large socket on a bar or something, because the high pressure air can actually push down on the piston and allow the engine to rotate, and the bits will then fall down inside.
So, for each cylinder that you are removing the glow plugs from you need to get the piston to t.d.c. first before trying to remove the glow plug. To do this, you need to find the timing pointer, and the line scribed into the side of the harmonic balancer. When these are lined up with each other, it is an indication that #1 piston is at t.d.c.! Ok, next, for each 1/4 turn of the engine in a clockwise direction as seen from the front of the truck, the next piston in the firing order will be at t.d.c. The firing order of the 6.9l engine is 12734568. Each piston is mated with another for balance. so, this means that when #1 is at t.d.c. so will another. It happens to be #4. 2/5, 7/6, 3/8 are matched too. Thus, when #1 is at t.d.c. you can also work on #4, turn 1/4 turn clockwise, and then you can now work on #2 and #5 and so on....
That's it!! I have now made it a practice and I recommend it to anyone, that every time you decide to remove those glow plugs, to follow this procedure, and you will at the very least lessen your chances of getting into trouble. Unless your controller has failed and left the plugs on too long, chances are they will just come up/out without any problems at all. They do get carboned up sometimes, and a bit of wd40 squirted down on them can sometimes help.
Finally, this is just my personal experience, but I did do some testing on 4 brands of glow plugs, and found that when hooked directly to a battery and left, that some plugs burned out in as little at 10 seconds, and other were still intact after 40 seconds. But, even worse, were the ones that when they did burn out, distorted or bent such that they would be all but impossible to remove even using the methods I've described above. The Autolite brand was the worst. 10 seconds and they died, and distorted!! These were the ones I had to pull my heads off to recover. I do not recommend anyone use this brand!!
check this out
Champions were not much better, and they died in about 12 seconds. Lucas and Bosch both did better, lasting about 20 seconds, and finally Beru(motorcraft) I left on for over 40 seconds, and they didn't distort, or burn out. There is one other type, that are apparently a modified to fit Gm/Ac glow plug which is called "constant duty". Advertising says that they can be left on indefinately, and will not be harmed!! While at $38 each Canadian, I didn't want to take a chance on burning one out, but I have put them in my truck, and they have worked very well for me. I consider the high cost insurance.The only place that I know of where they can be purchased is in Canada at Diesel Auto services but he will ship them to the U.S. too.
So, in conclusion, I can say there is no guarantee that every time you remove glow plugs they will come out intact. But, if you take your time, and follow this method described above, you may improve your chances of not learning first hand how to replace your own head gaskets!!! Best of luck!!