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| AlanMcR Expert Date registered: Apr 2006 Location: US, CA, Los Altos Vehicle(s): G300DT E300DT 230SL Posts: 3500  | Broken Glow Plug removal on OM606, OM605, OM604 engines. The OM60x series of 4 valve Mercedes diesels are notorious for seizing glow plugs. Apparently the plugs don't seat properly at the combustion chamber end. This allows carbon to get packed in around the barrel. Over time the plugs become glued into place. The narrow neck between the hex nut and the threaded shaft isn't up to the torque required to untwist the plug and it snaps off. The problem has nothing to do with the threads sticking, though the aluminum and steel combination can't be helping. If you have a broken off glow plug, you are faced with a choice: A: Remove the head and take it down to a machine shop to have the plug machined out -- OR -- B: Make a simple puller to yank out the plug. This page describes how to do (B) Tools:
If you make a mistake you will be going to option (A). 1) Remove the glow plug's hex head and center electrode. Vice grips will do nicely. Just tear the off the hex part and then clamp onto the electrode and lever it out. The electrode is a good 4cm long and can be welded in there pretty well. It has to come out for the next steps.
2) Freeing the threads Drill out the threaded portion of the plug. Use a 1cm/.4" drill bit to drill the first 15mm of the plug body, as measured from the surface of the head. Drill exactly in the center. The hollow body makes this relatively easy. This gets you through the threaded portion of the plug. The threads of the glow plug are still in the head. Leave them there as the steel spiral helps protect the much softer aluminum threads in the head. Now the remainder of the plug can be pulled straight out, rather than needing to be turned. Blow out the chips.
Drill out the hollow part of the plug with the 5mm drill from the M6 Tap set. Go in at least 35mm and not more than 45mm, as measured from the surface of the head. Blow out the chips. 4) Tapping the body Use a M6x1.0 tap to make threads on the inside of the glow plug body as far in as the tap will go smoothly. Whatever you do, don't break the tap in there. Take your time. Blow out the chips. (The picture shows larger tap, use an M6 for this step) 5) Building the puller Thread the M6 nut onto the M6 bolt. Then stack some washers on to the bolt and thread it as far as it can go into the (now threaded) glow plug. Just get it snug, no real force is required. 6) Pull the plug Turn the nut clockwise so that it gets further away from the bolt head. This will force the plug out of the head. The first real resistance will be firm. After the grip of the carbon gunk is broken it will move easier. Then it will stop moving. This means that the plug is jammed up against the washers. Unscrew the puller and pry out any bits (thread rings, etc) that are easily removable. Reassemble the puller with a 13mm x 3/8" socket instead of the washers. The hollow formed by the socket will allow the plug to move further out of the head. 7) Success! When the bolt head starts to turn easily, you will have pulled the plug out far enough that you can yank it out by hand. This is what you should see: 8) Cleanup Suction out the chips. Then, insert some wadded up tissue paper into the hole. Now you can clean up or repair the threads. I've been able to use a dental pick to separate the left over threads from the plug which are still in the head. Once a long enough piece has been freed, use a hemostat clamp to spiral the rest out. If you were careful, the threads should be good and you can install a new plug. If the threads are damaged, install a Time-Sert or Heli-coil (M12x1.25 x 15mm). Remember to ream out the glow plug hole (Klann KL-0369-13)
9) End result As an experiment, I've chosen to coat the entire body of the plug with Hylomar HPF. Aside from sealing the nose and threads this sealant is fairly temperature stable and may fill up the space that would otherwise fill up with carbon. It never hardens. Edited by AlanMcR 9/13/2010 12:19 PM (PullingGlowPlug0.jpg) (PullingGlowPlug1.jpg) (PullingGlowPlug2.jpg) (PullingGlowPlug3.jpg) (PullingGlowPlug4.jpg) (PullingGlowPlug5.jpg) (PullingGlowPlug6.jpg) (OM60xGlowPlug.JPG) (GlowPlug.jpg) Attachments ----------------  PullingGlowPlug0.jpg (102KB - 47 downloads) PullingGlowPlug1.jpg (115KB - 37 downloads) PullingGlowPlug2.jpg (113KB - 32 downloads) PullingGlowPlug3.jpg (103KB - 50 downloads) PullingGlowPlug4.jpg (101KB - 41 downloads) PullingGlowPlug5.jpg (98KB - 48 downloads) PullingGlowPlug6.jpg (115KB - 33 downloads) OM60xGlowPlug.JPG (64KB - 43 downloads) GlowPlug.jpg (49KB - 35 downloads) | |
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| Allister779 Date registered: Sep 2007 Location: Alberta Vehicle(s): 1990 300GD  | ||
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| AlanMcR Expert Date registered: Apr 2006 Location: US, CA, Los Altos Vehicle(s): G300DT E300DT 230SL Posts: 3500 | ||
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| Allister779 Date registered: Sep 2007 Location: Alberta Vehicle(s): 1990 300GD | ||
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| stevegsmith Expert Date registered: Apr 2006 Location: SF Bay Area, CA USA Vehicle(s): 82 300GD WVO, 06 Jeep Lib CRD B99 Posts: 1301  | ||
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| AlanMcR Expert Date registered: Apr 2006 Location: US, CA, Los Altos Vehicle(s): G300DT E300DT 230SL Posts: 3500 | ||
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| Aircruiser Extreme Veteran Date registered: Aug 2011 Location: Atlanta GA Vehicle(s): 2000 G500, 1986 300GD, 2017 Porsche Cayenne Hybrid Posts: 364  | ||
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| sean Member Date registered: Dec 2015 Location: austin texas United States Vehicle(s): 88 300gd 460 swb right hand 85 280ge 617a turbo di Posts: 48  | ||
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