Repairing glow plug insert threads in cylinder heads and extracting broken glow plugs.

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Finguy
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Repairing glow plug insert threads in cylinder heads and extracting broken glow plugs.

Post by Finguy »

Hi to all.

Thought I could share a little story about how things can go wrong with a simple task of changing glow plugs to my 2.7HDI. Simple job to strip top of the engine and just change these... Or so I thought.

Two of the glow plugs were already broken by previous owner and one I broke while twisting it open. Glow plugs snapped right above the threads.

No way I was going to strip heads from the car as it is pretty difficult task to do. Easier would be just to lift engine off if starting to do that.

So I ordered broken glow plug removal set and glow plug tip removal set from Laser tools.

After few hours of work and with little extractor modification, I got the broken glow plugs pulled out.
Broken glow plugs removed and extractor sets on background.
Broken glow plugs removed and extractor sets on background.
I was so happy that I didn't need to strip cylinder heads from the car.

BUT...

When I started to tighten new set of plugs in place, with those three that I had to extract, the threads on cylinder head gave up. Quite a problem I had now.

Apparently they worn just enough when drilling those old plugs out, that they didn't hold.

So had to tap new threads some how and this is what me and my friend came up with:
Bushing made out of M12 bolt with hole drilled on center and tapped with M8x1.0 thread.
Bushing made out of M12 bolt with hole drilled on center and tapped with M8x1.0 thread.
Glow plug threads nicely inside the bushing.
Glow plug threads nicely inside the bushing.
That bushing you see is made out of M12 bolt with 7mm hole drilled on center and tapped with correct M8x1.0 thread that plugs have. About 10mm longer than the threads on glow plug, just to make sure that they reach deep enough in the cylinder heads and don't prevent tightening those glow plugs.
Helicoils are with M8x1.25 so couldn't use those. There is at least one official threading insert, called Time-sert but it's a bit pricy and I was in a hurry.
...and want to try to do everything by myself if possible... :D

Next part was as follows:

Enlarge the glow plug hole in cylinder head by drilling with 10,5mm bit. Drill just a bit further than what the length of the bushing is. Before starting to drill, tuck a tiny peace of paper inside the hole. This way no chips enter the combustion chamber. Also it is recommended that you remove glow plug next to your to be machined one so you can insert some rod into the hole and match that angle when drilling. It's vital that the angle, when drilling, is exactly in line with the hole.
Enlarging the glow plug insert hole with 10,5mm drill bit.
Enlarging the glow plug insert hole with 10,5mm drill bit.
After drilling, use shop vacuum cleaner with small tip to suck the chips and the paper from the hole.

Next thing is to tap new M12 thread to the enlarged hole. Again put a peace of paper in the hole and use cutting grease when tapping. And again, watch those angles!
Tap I used for the M12 threads.
Tap I used for the M12 threads.
Tapping the enlarged glow plug insert hole.
Tapping the enlarged glow plug insert hole.
After tapping, clean everything again and next thing to do is to insert the bushing.

I did it with a nut and bolt. Screw nut to the bolt and bushing against the nut and tighten the nut to the bushing. This way you can tighten the bushing in place, loosen the nut and remove the bolt.
Bushing tightened to bolt with nut. This way you can easily tighten the bushing in place, loosen the nut and remove the bolt.
Bushing tightened to bolt with nut. This way you can easily tighten the bushing in place, loosen the nut and remove the bolt.
Now just tighten the bushing on place. Use Locktite 270 threadlocker or similar to lock the bushing permanently on place.

I did something with my phone and lost few of the photos, like when inserting the bushing and finished work but I trust that you don't need photos for that.

Next step is just to tighten the new glow plug in its place.
Did this same job with two more plug inserts and now they hold and car starts perfectly. :)

In the end, saved a lot of money and hours by not having to strip the heads from the engine. Wouldn't say that this is too difficult for someone to follow, just make sure to watch the angles all the time when drilling. Besides that, peace of cake.

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NewcastleFalcon
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Re: Repairing glow plug insert threads in cylinder heads and extracting broken glow plugs.

Post by NewcastleFalcon »

Well done from me, I am no stranger to glow plugs with snapped off tips and my cautionary tale is told on this thread entitled "Glow Plugs Annihilate 2.0Hdi Xsara Picasso". .

While hoping to revive the vehicle, the sheer pain in the neck factor of cylinder head removal on that vehicle to inspect the damage done, has as the thread title states annihilated a very good car. I have yet to see a thread where someone has removed the cylinder head from a Xsara Picasso 2.0Hdi....hoplessly restricted space behind the engine, and effectively a full engine out job to remove the head.

I left the tips in, but eventually one dropped out into the cylinder and wreaked its havoc.

Maybe a bit of info on your kit..cost, how you used it may help others. Clearly from my experience its not that good a strategy just to leave the snapped off bit in situ...it will eventually fall out...and if the tool set you bought was effective it may save others the hassle.

Regards Neil
Last edited by NewcastleFalcon on 15 Apr 2017, 18:39, edited 1 time in total.

Finguy
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Re: Repairing glow plug insert threads in cylinder heads and extracting broken glow plugs.

Post by Finguy »

Truly sorry that you have such a huge problem from such a small tip. :(
These were the two sets I used, first is for glow plug removal and second one was just a precaution in case that I snap an tip while extracting those glow plugs:
http://www.ebay.co.uk/itm/390990194007
http://www.ebay.co.uk/itm/262699021026

Two videos on how these work:



My initial idea was that if the first extractor won't work, I'll then use the second one first to drill and tap into the electrode and then really gently drill almost all of the body out, extract the electrode and clean the hole. But as I found out and because of previous jobs removing broken glow plugs from removed cylinder heads, I knew that after I get the threaded part drilledout off with just about 3cm body left in, it comes of with little effort.
Good thing with this engine is that I had the room to do all this. Not sure how your 2liter engine is orientated.
But like said in the original post, had to tweak the extractor a bit. One of the glow plugs was so tight (that shortest on the photo) that after tapping it and trying to extract, threads gave up and extractor slipped of.
I knew that it needed just a bit of twisting while tapping it up and down to start come off so I drilled a little further inside the glow plug body and tapped with left handed thread. Screwed an left handed thread bar inside the body and attached that to self made slide hammer. Then just gently counter clockwise twisting (bar screws even more tightly to body while body starts to loosen) with tapping gently with slide hammer and it came of. Next thing would of been to drill the whole body out and trying to extract the electrode but happily there wasn't need.

Sorry for not having any photos on this procedure, it buggers me a bit that after all that pain in the *** job, didn't take any photos to help others.

But main thing is to stay calm. The body is stuck quite firm on those threads inside the cylinder head that reach quite deep with a bit of swelling at the tip of the glow plug body.
You just have to drill the threading part from the glow plug of and then I suggest that you modify a sliding hammer to tap the plug out.
That screwed to pull extractor isn't best because of the static pulling motion without any vibration.
Vibration combined with pulling motion is the second best option. Best is the one mentioned, left hand threaded bar screwed inside the body with sliding hammer attached. Then you can apply counter clockwise twisting combined with vibration and upward pulling motion.

Edit: Actually found two photos, first is self made sliding hammer (made out of struts piston rod and about 20 washers welded to make the hammer) with extracted glow plug at the end and second is the glow plug where you can see how that end is swollen when it's tightened against the sealing lip in the cylinder head.
Slider hammer made out of struts piston rod with quite a few washers welded together to make the hammer.
Slider hammer made out of struts piston rod with quite a few washers welded together to make the hammer.
Swollen end of the glow plug.
Swollen end of the glow plug.
Last edited by myglaren on 19 Feb 2017, 12:56, edited 1 time in total.
Reason: YouTube tags

Bick
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Re: Repairing glow plug insert threads in cylinder heads and extracting broken glow plugs.

Post by Bick »

Hi Finguy - looks like you are a good engineer my friend and thank you for an excellent post.

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white exec
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Re: Repairing glow plug insert threads in cylinder heads and extracting broken glow plugs.

Post by white exec »

Yes indeed. Thank you for posting the details of the process along with good practical advice and cautions.
This could make the difference between an engine/car being scrapped or rescued.

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Pug_XUD_KeenAmateur
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Re: Repairing glow plug insert threads in cylinder heads and extracting broken glow plugs.

Post by Pug_XUD_KeenAmateur »

A seriously impressive account.

A quick leaf through the various Glow Plug threads and I find myself wondering whether someone can point me to a post detailing how to give oneself the best possible chance of not snapping 'em in the first place, most of the posts seem to deal with the 'aftermath'.

Glowplug changing is one of those jobs I've always avoided, so the garage did mine a couple of years back, but all being well I'll be doing a HG replacement on one of my spare lumps (XUD na) in the summer, knowing that despite its 275k and severely blown HG it runs lovely; and it'd be simplest if I don't snap em.

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Re: Repairing glow plug insert threads in cylinder heads and extracting broken glow plugs.

Post by myglaren »

Pug_XUD_KeenAmateur wrote:A seriously impressive account.

A quick leaf through the various Glow Plug threads and I find myself wondering whether someone can point me to a post detailing how to give oneself the best possible chance of not snapping 'em in the first place, most of the posts seem to deal with the 'aftermath'.

Glowplug changing is one of those jobs I've always avoided, so the garage did mine a couple of years back, but all being well I'll be doing a HG replacement on one of my spare lumps (XUD na) in the summer, knowing that despite its 275k and severely blown HG it runs lovely; and it'd be simplest if I don't snap em.
I often think that as James (Hellrazor) recommends for spheres that a periodic loosening half a turn and re-tightening would help prevent them from becoming difficult to remove without damage.
On the other hand they might break when attempting that so there is the counter-argument that "If it's not broke then don't fix it"! or Leave Well Alone.

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white exec
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Re: Repairing glow plug insert threads in cylinder heads and extracting broken glow plugs.

Post by white exec »

Aren't they normally fitted with a smear of copper grease? Maybe not the factory originals, though...

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Re: Repairing glow plug insert threads in cylinder heads and extracting broken glow plugs.

Post by Pug_XUD_KeenAmateur »

white exec wrote:Aren't they normally fitted with a smear of copper grease?
I haven't a scooby, would be nice if these were, and at 275k its pretty safe to assume they're not original; but to a cynic such as me (is it cynicism or realism) am inclined to think that someone paid to do a job would likely not have taken the few seconds necessary to bother.

Me thinks worthwhile slathering some diesel around em to hopefully work down to the threads. What of heating the head with a (Plumbers) blowtorch also, to mimic 'hot engine' conditions?

Finguy
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Re: Repairing glow plug insert threads in cylinder heads and extracting broken glow plugs.

Post by Finguy »

I have always used copper paste with my diesels when changing glow plugs and those ones needed second change, they always came off very easy because of the copper paste.

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Re: Repairing glow plug insert threads in cylinder heads and extracting broken glow plugs.

Post by superloopy »

Plusgas'sed mine just recently. Despite loadsa other problems the two i've managed to do gave up easily.

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Re: Repairing glow plug insert threads in cylinder heads and extracting broken glow plugs.

Post by Pug_XUD_KeenAmateur »

Thanks for the suggestions Guys (have we got any 'Girls' here?)
Laid the engine back and slathered a loada diesel around it for the mo, leave it a couple of days & have a go me thinks, Glowplugs are shiny implying poss' recent-ness. I note with suspicion that No.4 / 1 (Gearbox end) has at least 4 threads showing where others have only 1.

Was out there 'practice welding' a threaded rod joiner to a Torx Bolt to mimic the one that I can't get out of my Drivers Door top hinge. Went really well, didn't break when I gave it some welly with a socket & T-Bar. Fingers crossed for the 'real thing' soon.
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Finguy
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Re: Repairing glow plug insert threads in cylinder heads and extracting broken glow plugs.

Post by Finguy »

Bick wrote:Hi Finguy - looks like you are a good engineer my friend and thank you for an excellent post.
Thank you. Well, I consider myself as an weekend greace monkey. :P Wouldn't (not to mention couldn't) do any total engine or transmission rebuild but like in this case, plugs were already broken so can't do any more harm if trying to pull them out. :D

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Re: Repairing glow plug insert threads in cylinder heads and extracting broken glow plugs.

Post by Finguy »

Pug_XUD_KeenAmateur wrote:A quick leaf through the various Glow Plug threads and I find myself wondering whether someone can point me to a post detailing how to give oneself the best possible chance of not snapping 'em in the first place, most of the posts seem to deal with the 'aftermath'.
I'd recommend using some penetrating oil and let it sit for at least a day, preferably start soaking them week before if they seem to be stuck.
Then just before removal, drive car to operating temp. Then to remove them, gently turn to loosen just a bit and back to tighten. Back and forth. Take your time and hopefully they'll come off. Some vibrating opening tool should help tremendously, check the link at the end of the post.

If they're stuck, it's usually usually because of

- electrode; carbon buildup or swollen and on both occasions you can't just twist open but have to allow carbon to break bit by bit or tip stretch a bit to fit thru hole. Have seen such a swollen tip that in no way it was possible to remove from the glow plug hole.
-body of the glow plug; stuck by carbon buildup because leaking seal at the combustion chamber end.
-threads; gets a bit deformed ether on the glow plug or aluminium heads, usually by over tightening. Body gets pressed to tight and possibly tip of the body swollens a bit.

One or some kind of neat combination. :D If you look at my broken plugs, one that is shiny came of without any effort after I drilled the thread out as its seal has kept. Two others had carbon buildup between insert and the body and those needed a lot more persuasion after drilling.

In all cases heat with soaking helps and some high frequency vibrating opening tool.
I would recommend some tool like this one if you fear or have already seen that glow plug doesn't even budge via ratchet: http://www.welzhwerkzeug.com/products/p ... uct_id=507

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Re: Repairing glow plug insert threads in cylinder heads and extracting broken glow plugs.

Post by Pug_XUD_KeenAmateur »

Thanks Finguy for the detailed advice and link. Appreciate the time you took with it. Fingers crossed for the actual removal :)

Edit 25 Feb.... they came out lovely, perhaps in part for the laying the engine on its back and a liberal application of diesel around the threads, but who's to know.

I took the Fuel Pump off first (Lucas Roto) and put it aside to carry 'just in case', noting that none of my extensive collection of bolts seemed to fit the holes in the pulley to thread through & push against the head to facilitate getting it off if its stubborn. Thankfully, it came off easily anyway, but its a bit weird. Anyone know what size they are, maybe imperial?
Last edited by Pug_XUD_KeenAmateur on 25 Feb 2017, 20:47, edited 1 time in total.