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Broken Glow Plug removal on OM606, OM605, OM604 engines.
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Posted 9/11/2010 12:58 AM
AlanMcR
Expert




Date registered: Apr 2006
Location: US, CA, Los Altos
Vehicle(s): G300DT E300DT 230SL
Posts: 3283
2000
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:

  • vice grips
  • drill motor
  • 1cm drill bit (13/32" is just right, 7/16" might be too big)
  • M6 x 1.0 Tap and drill set
  • hardened M6 x 1.0 bolt, at least 6cm long
  • hardened M6 nut
  • assortment of washers
  • a 13mm X 3/8" standard depth socket
  • patience, this is a really expensive head. 


0) Read and understand every step before beginning any work.

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.


3) Drilling the body

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.  We'll see in 50Kmiles or so. UPDATE: So far so good.  All plugs that got the full Hylomar coating have come out easily.  Also, the plugs have lasted longer, so the slippery sealant may be helping them seat better.



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
----------------
Attachments PullingGlowPlug0.jpg (102KB - 18 downloads)
Attachments PullingGlowPlug1.jpg (115KB - 13 downloads)
Attachments PullingGlowPlug2.jpg (113KB - 14 downloads)
Attachments PullingGlowPlug3.jpg (103KB - 13 downloads)
Attachments PullingGlowPlug4.jpg (101KB - 17 downloads)
Attachments PullingGlowPlug5.jpg (98KB - 15 downloads)
Attachments PullingGlowPlug6.jpg (115KB - 15 downloads)
Attachments OM60xGlowPlug.JPG (64KB - 15 downloads)
Attachments GlowPlug.jpg (49KB - 15 downloads)
#177278
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Author
Posted 9/11/2010 10:41 AM
Allister779



Date registered: Sep 2007
Location: Alberta
Vehicle(s): 1990 300GD
500
Re: Broken Glow Plug removal on OM606, OM605, OM604 engines.

Great write up! I think this would have saved me some cash last year on my Wifes VW.

Can you post a picture of your 606 plug so I can compare it to a 603 plug? I haven't noticed the carbon on mine when I've pulled them out and I'm trying to figure out if I've just been lucky or it's a different design of plug.

#177291 - in reply to #177278
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Posted 9/11/2010 11:23 AM
AlanMcR
Expert




Date registered: Apr 2006
Location: US, CA, Los Altos
Vehicle(s): G300DT E300DT 230SL
Posts: 3283
2000
Re: Broken Glow Plug removal on OM606, OM605, OM604 engines.

I've updated the original posting with a picture of a new plug. 

The basic technique is useful with other motors. This particular how-to was posted on Google Pages for a long time. Several people have told me that they modified this how-to for other motors, but I've not captured the dimensions required.

Klann, the tool making company, actually has a patent (US20060260110) on a tool that uses a similar technique to remove this particular glow plug.  Their system doesn't attempt to save the threads in the head.  The tool was >$500 and I think it is out of production.   Franky, I think my method is much better.  Then again, I might be biased.  The patent is worth looking at since it comes with beautiful drafting drawings of the plug and head. 



Edited by AlanMcR 9/11/2010 11:46 AM
#177294 - in reply to #177291
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Author
Posted 9/11/2010 2:51 PM
Allister779



Date registered: Sep 2007
Location: Alberta
Vehicle(s): 1990 300GD
500
Re: Broken Glow Plug removal on OM606, OM605, OM604 engines.

Yes, that plug is different. The section between roughly 60mm and 100 mm in your picture is much shorter on the 603 engine. Perhaps not allowing the carbon build up to the same level.

I'm not familiar with Hylomar HPF, but I was wondering if using anti-seize in the same area would work? It would take up the space so the carbon can't, also reducing some of the "welding" that occurs between the plug and the head...
#177308 - in reply to #177278
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Posted 11/19/2010 12:05 AM
johnbrnrd
New user


Date registered: Nov 2010
Location: Chicago, IL
Vehicle(s): GD 300
Posts: 1

RE: Broken Glow Plug removal on OM606, OM605, OM604 engines.

Hi thank you for providing information on the replacement of the glow plug, it has been my problem for a week now and knowing that because the threads of it are sticking I have opted to put also a hylomar in mine since it gives proper seating on the engine. thank you so much sir!

Edited by johnbrnrd 11/22/2010 5:48 AM
#180332 - in reply to #177278
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Posted 11/19/2010 2:58 PM
stevegsmith
Expert




Date registered: Apr 2006
Location: SF Bay Area, CA USA
Vehicle(s): 82 300GD WVO, 06 Jeep Lib CRD B99
Posts: 1301
1000
RE: Broken Glow Plug removal on OM606, OM605, OM604 engines.

Nice job McRickles! You clever devil.
#180348 - in reply to #177278
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Posted 5/29/2011 9:43 PM
camo
New user


Date registered: May 2011
Location:
Vehicle(s):
Posts: 1

Re: Broken Glow Plug removal on OM606, OM605, OM604 engines.

hi, I have a jeep liberty crd and one of the glow plugs broke just like this at the head. I read the instruction and saw the pic but I have two question. do you think this jeep work on my jeep CRD?
will this method pull the plug out or unthreaded?
#190497 - in reply to #177278
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Posted 5/31/2011 12:08 AM
AlanMcR
Expert




Date registered: Apr 2006
Location: US, CA, Los Altos
Vehicle(s): G300DT E300DT 230SL
Posts: 3283
2000
RE: Broken Glow Plug removal on OM606, OM605, OM604 engines.

The basic concept will work to remove your plug.   Measure a new plug and see if it matches the one shown.  The key things to measure are the length and diameter of the shaft and the threads. 
#190519 - in reply to #177278
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Posted 10/6/2017 12:06 PM
Aircruiser
Extreme Veteran




Date registered: Aug 2011
Location: Atlanta GA
Vehicle(s): 2000 G500, 1986 300GD, 2017 Porsche Cayenne Hybrid
Posts: 311
300
Re: Broken Glow Plug removal on OM606, OM605, OM604 engines.

Deleted. Nice work!

Edited by Aircruiser 10/12/2017 10:28 PM
#237327 - in reply to #190519
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