Broken Glow Plug Removal

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KAM

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I'm in the process of changing glow plugs on an MD2030 after short circuit and fire. The two difficult to access plugs came out OK. The centre plug which is easiest to access was already broken (possibly by recent previous owner) and possibly the cause of the short. Just trying to work out a method for 'removing the remaining plug. The engine starts OK so its a winter project. Easy outs dont work. The proposed method is to tap a left hand thread and loctite in a high tensile bolt. I'm just wondering whether to go straight for the tapping drill size or if I should try to remove the central electrode first. The top of the electrode is surrounded by viton with ceramic powder lower down. One option may be to punch the electrode down to improve the centering of the tapping drill. Has anyone done this. Any tips appreciated. Trying to avoid a head off last resort.
 
Personally, I would leave it alone. The engine will start fine on the remaining two, at worst it will missfire on that cylinder for a few seconds after starting from cold. If you start using drills etc, you risk the ceramic part breaking off and the debris dropping into the cylinder. Then it's a head off. You now have two new glow plugs, I would leave it until the head has to come off sometime in the future and you can work at it on the bench or take it to an engineering shop. Make sure you insulate the metal bar that goes to the middle glow plug so that it doesn't short.
 
No metal showing? It might be possible to weld a bolt on if there is. Run the engine up to full temperature before attempting to unscrew.
 
Yes weld a bolt on then a penetrating fluid, and then run engine to full temp and then try and remove it!
 
black mercury said:
Personally, I would leave it alone. The engine will start fine on the remaining two, at worst it will missfire on that cylinder for a few seconds after starting from cold. If you start using drills etc, you risk the ceramic part breaking off and the debris dropping into the cylinder. Then it's a head off. You now have two new glow plugs, I would leave it until the head has to come off sometime in the future and you can work at it on the bench or take it to an engineering shop. Make sure you insulate the metal bar that goes to the middle glow plug so that it doesn't short.
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I'm with this ... if engine is a good starter - then it really only needs to 'glow' on one or two ....

Many other engines only have one glow in the air intake .... my 4cyl Perkins has only the 'ignitor' in the air intake.
 
savageseadog said:
I agree that the egine will run as is but will the glow plug eventually disintegrate?
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Glows are an inessential extra in my view.
With a couple working you've got traction.
Of course you'd like to keep your mill nice and tidy but damage to right a cosmetic is a high price to pay. Roll on as is.

PWG
 
Just did a trial on one of the old plugs. The steel was very soft and it was very easy to drill down the centre and tap a good concentric thread without a pilot. The bolt sheared at 20Nm so there is a reasonable chance of success with a 12.9 bolt. Not a summer job though.
 
The electrode snapped on my bmc.. That still left me with 3 other news glowplugs.. Decided head off to remove is never going to happen !
Had the new plug with spanner for plug and wire terminal ready for a quick change and carried on sailing. Its got to blow out sometime as only friction is holding it in ?
About two months later there was a bang, a loud exhaust noise like a steam train and a boat full of exhaust smoke... I mean how the hell does a 4mm glow plug hole fill up an entire boat in seconds? Took just a few minutes to put the new plug in and i was away again !
 
Two glow plugs broke while being replaced on my wife's Hyundai, they were left in but it starts instantly now on the two that were replaced. Breaking plugs on removal is very common apparently and there are special tools and even emergency specialists to deal with them.
 
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