CDI broken glow plug removal tool- how does it work? - PeachParts Mercedes-Benz Forum

ROLLGUY · #1 03-13-2020, 05:49 PM

I ordered a broken glow plug removal tool, but there was no instructions with it. Has anyone used one of these, or know the procedure to use it?

Skid Row Joe · #2 03-13-2020, 06:48 PM

Rich,
I'd do a YouTube search on it, generically to see if you might gain some insight. Try brand naming it too. Report back, as you go with the kit.
Thanks

.

ROLLGUY · #3 03-13-2020, 07:18 PM

Quote:

Originally Posted by Skid Row Joe

Rich,
I'd do a YouTube search on it, generically to see if you might gain some insight. Try brand naming it too. Report back, as you go with the kit.
Thanks

.

Now why didn't I think of that?
https://youtu.be/W1JiWt_kesU

Skid Row Joe · #4 03-13-2020, 07:26 PM

Quote:

Originally Posted by ROLLGUY

Now why didn't I think of that?
https://youtu.be/W1JiWt_kesU

Excellent, Rich! 👍

ROLLGUY · #5 03-13-2020, 07:33 PM

My niece's car (formerly my first CDI) has a broken off glow plug, and two more bad ones. I want to be able to replace all of them, so I need to have the tool handy and know how to use it. Hopefully I will only need to use it for the one plug.

RunningTooHot · #6 03-17-2020, 02:53 AM

No personal experience, but speculation combined with a little bit of memory about researching how to do a 606 plug:

You first need to snap off the electrical connector by twisting the hex portion. The small (black) drills and taps are used to gut the heating element out from the GP body. Drill, tap, and slide hammer the guts out.

The reverse rotation drill bits are used to prep the body for tapping. If you're very VERY lucky, the reverse drill bit may dislodge the body and you'd be done. But that's unlikely.

I can't tell from the picture, but the large taps in the kit should be (?) reverse threaded too. So the next step is to tap (thread) the GP body. If the kit is specifically for the CDI glow plugs, the drill bits may be sized to the appropriate depth, otherwise you'd need to account for not going too deep.

Here's the speculative part: By carefully threading the tap as deep as it can go, eventually it will bottom out and then you should have the ability to put a lot of twisting force to get the GP out. By drilling and tapping, you will have taken away a fair amount of material from the GP body, which should theoretically allow a bit of malleability which would make it easier to take out.

The horror part of this is IF you apply too much torque, you could possibly snap the hardened steel tap inside the GP body. At that point, you'd need to do a Marie Antoinette procedure, then find a good machine shop to do some EDM magic on the head. And this is ALL predicated on your ability to make sure your drilling is in perfect alignment with the GP during the first steps in the surgical procedure. That part scares me. I have nightmares about seeing aluminum coming up the drill bit flutes instead of steel.

Now you know why I still have a broken GP on my '98 E300.

It just seems like too high of a risk/reward ratio to try it on a car that doesn't see severe cold conditions.

No guarantees on this - I could be all wrong... in which case I'll look forward to being informed of the correct procedure.

ROLLGUY · #7 03-17-2020, 03:49 PM

Quote:

Originally Posted by RunningTooHot

No personal experience, but speculation combined with a little bit of memory about researching how to do a 606 plug:

You first need to snap off the electrical connector by twisting the hex portion. The small (black) drills and taps are used to gut the heating element out from the GP body. Drill, tap, and slide hammer the guts out.

The reverse rotation drill bits are used to prep the body for tapping. If you're very VERY lucky, the reverse drill bit may dislodge the body and you'd be done. But that's unlikely.

I can't tell from the picture, but the large taps in the kit should be (?) reverse threaded too. So the next step is to tap (thread) the GP body. If the kit is specifically for the CDI glow plugs, the drill bits may be sized to the appropriate depth, otherwise you'd need to account for not going too deep.

Here's the speculative part: By carefully threading the tap as deep as it can go, eventually it will bottom out and then you should have the ability to put a lot of twisting force to get the GP out. By drilling and tapping, you will have taken away a fair amount of material from the GP body, which should theoretically allow a bit of malleability which would make it easier to take out.

The horror part of this is IF you apply too much torque, you could possibly snap the hardened steel tap inside the GP body. At that point, you'd need to do a Marie Antoinette procedure, then find a good machine shop to do some EDM magic on the head. And this is ALL predicated on your ability to make sure your drilling is in perfect alignment with the GP during the first steps in the surgical procedure. That part scares me. I have nightmares about seeing aluminum coming up the drill bit flutes instead of steel.

Now you know why I still have a broken GP on my '98 E300.

It just seems like too high of a risk/reward ratio to try it on a car that doesn't see severe cold conditions.

No guarantees on this - I could be all wrong... in which case I'll look forward to being informed of the correct procedure.

All great info, thanks. The thing that makes it more imperative that I get the broken plug out, is that the CDI will continue to illuminate the CEL until the bad plug (and now plugS) are replaced. When I got the car, the one broken plug caused the CEL to light. I welded a nut of the proper size onto a piece of tubing, and attached it to the engine. I then screwed a good plug into it, and connected the wire. The computer did not know any different, and the CEL remained unlit for several years. Just recently, two more plugs went bad, and the CEL is lit. If other things go wrong, my niece will not know any difference because the CEL is already lit.

RunningTooHot · #8 03-18-2020, 01:04 AM

Funny - we think alike... an added external aluminum tube holding the "spare" (7th) glow plug is precisely how I keep my CEL light off.

Considering the circumstances, it appears that you really do need to get those plugs out. The 606's are known for the potential nightmares of seized GP's, but I thought the CDI's didn't have the same problem. Perhaps it's less common on the 648's, but it's a bummer either way. Sorry to hear about your ordeal.

But then again, you've successfully tackled Black Death, so you'll likely come out okay with this. Just be super careful with the drilling. I do know that there was some sort of jig available for the 606's to help with drill alignment, but it was very rare due to it's cost. I wonder if there's a similar tool for the 648's?

jay_bob · #9 03-19-2020, 03:03 PM

R2H has the process mostly right. Done it on a 606 but from the linked video the process appears to be the same on the 648.

First it helps to visualize what is inside the glow plug.
The heater is in the tip (the ceramic part). To get electricity to the heater you have a solid rod that goes through the length of the glow plug down to the bottom of the steel part (where it transitions to the ceramic tip). The rod connects to one end of the heater coil and the other end of the coil goes to the steel tube to ground the heater element so current can flow.

The rod (also called the electrode) goes down inside the steel tube. There is an air gap between the electrode rod and the steel tube. This air gap provides electrical insulation between the electrode and the outer tube.

When you break a glow plug, you shear the steel tube, usually just below the nut. This is where the tube is threaded to hold it in the head.

So the first step is to get the electrode out of the way, leaving the hollow steel tube. This is normally done with a tool that grabs the end of the electrode and allows you to twist it which breaks the support at the bottom end of the electrode and allows you to pull it out.

This leaves you a hollow tube. However first you have to get rid of the threads. So the first drill in the kit is a pilot point bit, that is carefully selected to have the pilot point ride down the hollow tube and guide the larger part of the drill bit, to drill out the threaded portion of the tube, and hopefully not contact the threads in the head.

Hint- use a magnet to collect the shavings produced in this step. The plug tube is steel and the head is aluminum. If you are making shavings that don’t stick to the magnet, that is a danger sign you are drilling away head material.

Once you have drilled the threaded part of the tube away, now you have the rest of the hollow tube still holding the tip of the glow plug in the head.

I then took an intact old glow plug and sawed it off in a vice just below the threaded part. The electrode and terminal assembly just fell out leaving me a collar (the nut and threads with a hole). I bored it out large enough that the tap would slide through. I screwed this into the head to protect the threads in the head for the next step.

Now you want to take an intact glow plug (either a new one or an old one that came out whole) and set up the second drill bit to know how far you can drill down the hollow tube before hitting the ceramic part or the taper. Most kits give you a collar to help control the depth. Normally this drill bit has left handed threads.

Once you have opened up the hollow tube now you can tap it for the extraction rod. Use a manual tap handle, grease the tap, and go slow and careful, and you will be fine.

Remove the collar protecting the threads now.

Once you have tapped the core then you insert the left hand threaded extraction rod and tighten until snug.

Some kits have a slide hammer and some have a screw jack that you tighten with a wrench. In either case you are applying pulling force to the extractor rod along the axis of the glow plug to force the plug out of the head (by pulling it, not twisting it).

Once you have pulled the broken plug out they include a right threaded tap to clean up the threads in the head. If you were careful on the drilling you should be able to install the new plug without any problems.

If however the threads got bugged then you will have to do a Time-Sert to repair the hole.

jay_bob · #10 03-19-2020, 08:05 PM

Quote:

Originally Posted by RunningTooHot

Now you know why I still have a broken GP on my '98 E300.

It just seems like too high of a risk/reward ratio to try it on a car that doesn't see severe cold conditions.

I have all the tooling you will need to fix this on your 606 for rental.

Check out this post OM606 glow plug change - one broke off and pm me if interested.

TimFreeh · #11 03-20-2020, 12:03 PM

As usual, a clear-concise and accurate portrayal of the issues by Jay-bob.

I did this repair using the pictured kit on an OM648 a couple of months ago and don't really have much to add to Jay-bobs comments. Couple of things from my repair.

1) the electrode in the hollow tube loosely fits inside the hollow tube, it really, really helps to be able to completely remove the old electrode before you begin drilling. In my case the old electrode kept jamming the drill bit up causing the drill to walk off-center from the central portion of the hollow tube. This is exactly what you don't want to happen and when your free-hand drilling with a really sharp bit it can make things more than a bit dicey.

2) on the OM648 you'll notice a cylindrical hole into which the glow plug is seated below the outer head surface, as I recall its about an inch in diameter and maybe 1.5 inches deep. This cylinder is concentric to the bore path of the glowplug and if you have the ability to custom-make a bushing on a lathe that seats into this cylinder you can use it as a guide to drill-on center. The kit pictured doesn't have any way to center the drill as you doing the delicate drilling - this seems to be kind of an oversight to me? Maybe the general population is better at free-hand drilling than I am. I have a lathe and made a bushing and I was sure glad I had the bushing.

3) As Jay-bob points out if you're careful you'll be able to clean-up the threads and install the new glowplug. If the threads are messed up don't bother trying to use a heli-coil spring type repair kit - I won't go into the details but I spent the better part of a week trying to get make it work. Just get the Time-sert thread repair kit - it works perfectly in about 1 minute.

This isn't a tough repair if you have the right tools - but it is high-stakes for sure!

Skid Row Joe · #12 03-22-2020, 10:02 PM

Quote:

Originally Posted by TimFreeh

As usual, a clear-concise and accurate portrayal of the issues by Jay-bob.

I did this repair using the pictured kit on an OM648 a couple of months ago and don't really have much to add to Jay-bobs comments. Couple of things from my repair.

1) the electrode in the hollow tube loosely fits inside the hollow tube, it really, really helps to be able to completely remove the old electrode before you begin drilling. In my case the old electrode kept jamming the drill bit up causing the drill to walk off-center from the central portion of the hollow tube. This is exactly what you don't want to happen and when your free-hand drilling with a really sharp bit it can make things more than a bit dicey.

2) on the OM648 you'll notice a cylindrical hole into which the glow plug is seated below the outer head surface, as I recall its about an inch in diameter and maybe 1.5 inches deep. This cylinder is concentric to the bore path of the glowplug and if you have the ability to custom-make a bushing on a lathe that seats into this cylinder you can use it as a guide to drill-on center. The kit pictured doesn't have any way to center the drill as you doing the delicate drilling - this seems to be kind of an oversight to me? Maybe the general population is better at free-hand drilling than I am. I have a lathe and made a bushing and I was sure glad I had the bushing.

3) As Jay-bob points out if you're careful you'll be able to clean-up the threads and install the new glowplug. If the threads are messed up don't bother trying to use a heli-coil spring type repair kit - I won't go into the details but I spent the better part of a week trying to get make it work. Just get the Time-sert thread repair kit - it works perfectly in about 1 minute.

This isn't a tough repair if you have the right tools - but it is high-stakes for sure!

My 606 had at least one heli-coil installed for a new glow plug. This was 8-years ago. So far, so good.

What is the link to the Time-sert thread repair kit? Would like to know where to purchase.

OK, so what is the doomsday downside here on the 606 and 648? A new head? If so, what's the turn key on each. Including the new head?