Stripped glow plug, how to fix?

GRY_03TDI

Member
Joined
Nov 25, 2006
Location
San Antonio
TDI
2003 Auto
Well, my 03 had a bad #2 glow plug so I replaced them all, but the number 2 plug threaded just fine and then got real easy (stripped). I pulled it back out and the first two threads on the plug were smoothed over. Can you fix this by getting a new glow plug, tapping the hole in the head and banging things around in the garage out of anger. I am thinking that the tap would be a 12mm with 1.0mm pitch. Can anyone verify this? Also, anyone in the Baltimore area done this before so I don't end up screwing the head so bad it as to be pulled.

Great first post, huh?:mad:
 

BugBug

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Aug 19, 2006
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Minnesota
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2001 Beetle TDI, 2005 New Beetle
I think the threads might actually be M11 X 1.0mm. In order to keep the shavings out of the cylinder, you will need to remove the head. Unless someone has a better idea to keep the shavings out of the cylinder. You might be ok if you chase the threads rather than drilling it out and inserting a heli-coil.
 

GRY_03TDI

Member
Joined
Nov 25, 2006
Location
San Antonio
TDI
2003 Auto
BugBug said:
I think the threads might actually be M11 X 1.0mm. In order to keep the shavings out of the cylinder, you will need to remove the head. Unless someone has a better idea to keep the shavings out of the cylinder. You might be ok if you chase the threads rather than drilling it out and inserting a heli-coil.

I was going to coat the tap in grease to catch the metal flakes. That is how most of the aftermarket supercharger kits have you tap the oil pan. Things may be different when working right above the cylinder though. Then change the oil after the initial startup. I was not planning on drilling and inserting a helicoil. Are you sure about the 11mm? I found the 12mm online and ordered that tap. Knowing my luck with all this it will be 11mm and I will have to order more stuff. Thanks for the reply!
 

brucep

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Oct 1, 2002
Location
Vermont, USA
TDI
peebs4u2
For a lasting fix... go with helicoil. Many autoparts stores will "rent out" a complete helicoil "kit" with all the fixin's and then charge you for what you used when you return it. That way - you do not have to purchase a tap... just pay for the helicoil you use.

Since there is about a 1/2 inch space between the threaded part of the head and the "sealing area" where the GP seats... I would think you may be able to plug that up with somthing below where you will be working with the tap. Then vacuum it out well.

Using grease may help... but be SURE, CERTAIN and CONFIDENT that you remove all the grease with degreaser (carberator spray, Isopropal alcohol..etc) - lest the helicoil may not stay in place.
 
Joined
Apr 1, 2007
Location
Green Bay, WI
TDI
'09, '14 Jetta
I'm there! Doing that!

90K, '03 TDI, and I just buggered the threads in a hole while trying to do a "routine" replacement of a bad GP. Deja Vu, no?

I was happy to see that others have done the same (I hate it when I invent a new failure!), but wondered what the end result was.

Before I start yanking the head, here the big question:

Did anybody heli-coil the hole with the head in place? If so, did it work????

I've replaced the timing belt, so I'm not afraid of pulling the head if that is required, but it is a heck of a lot of work!

Also: Getting the new insert perfectly aligned with the seating surface further down in the hole looks like a dicey proposition with a hand drill & tap. If the thread repair was done in place, was alignment of the hole a challenge?
 

whitedog

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Bend, Oregon
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2004 Jetta that I fill by myself
Somone mentioned inserting a foam ear plug in the hole to keep debis from gettinginto the head. That plus grease on the tap would be good.
 

ymz

Top Post Dawg
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2003 Jetta TDI Wagon, 2003 Jetta TDI Wagon
Yes, the foam earplug trick is very much needed here...

Some notes I've saved over the years:

The thread pitch is M10x1.00...

you could chase the threads with the correct size thread forming tap, NOT A THREAD CUTTING TAP. A thread forming tool creates threads by displacing metal, not by cutting.
http://www.precisiontwistdrill.com/techhelp/help_pages/thread_forming_prod_taps.asp
http://www.mcmaster.com/

"The tricky part of chasing the hole with your tapping tool of choice
is to synchronize the tap with the thread that is already there. If the top threads in the head are too messed up this may be difficult to do. Just go slow and check your work after a full turn or so. If it looks like you are off synch it may pay to use a 10mm drill with a depth limiting length of tubing slipped over the drill, or device of some kind on it and remove some of the messed up part of the thread. CAUTION! Make sure that you have a definite way to limit the depth of cut! - When you take off a small amount of material the drill will tend to grab and draw the bit down into the good threads.

Then when the thread chasing is done rinse the hole with WD40 and feel confident to blow compressed air across the top of the glow plug hole to clear the debris, take a long handled foam ended swab on the threads, grab and unscrew the ear plug and it should help to clean the threads as well. When you get the top of the ear plug to the top of the hole blow it off again with air and remove. The bottom of the hole that I worked on was clean of chips and was dry.

Another thing is to clean the glowplug if it's going to be reused. I wound up taking a die to clean the glowplug of aluminum that had bonded itself to the threads on the way out."

(I forget who posted that...)

Good luck,

Yuri.


 
Joined
Apr 1, 2007
Location
Green Bay, WI
TDI
'09, '14 Jetta
Hope springs eternal

Thank you for the quick advice! I now have some thread repair tooling on its way to me, a rental car for the week, a foam earplug in the hole, and with any luck, I'll be back in operation in a few days.

I'll post an update on how things turned out.
 

kramnnim

Veteran Member
Joined
Sep 28, 2004
TDI
'00 NB
I've been planning to replace the gp's in my two TDI's, but reading this post scares me... Is there some way to make sure the threads don't get stripped?
 

ymz

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kramnnim said:
Is there some way to make sure the threads don't get stripped?
Well, there are very few guarantees in the world...

First, to try to make sure the GP doesn't break as you're removing it, you can clean the area (air) and use some penetrating liquid to remove any corrosion that may cause the GP to stick - especially if your car is getting on in years and the GP's haven't been out in a long time... Then, pay attention that the socket sits squarely on the GP and you put rotating force on axis and not at an angle... (clean up the liquid if you used any...)

When putting the GP back, put some copper-based anti-seize compound on the thread... (just a bit)... put the GP gently back in the hole, and slowly turn it backwards (counter-clockwise) a little bit 'till it finds the groove entrance... a little shake may be helpful in getting it square... then you can start screwing it in (Clockwise) by hand, only switching to the socket and handle when you've gotten it in a turn or so... you should pay close attention to the amount of resistance to the turning action...

Don't over-tighten... (it's only 11 ft*lb - just snug with your hand close to the socket end of the ratchet...)

Yuri.

PS: with all this, the glow plugs can still break off as you're removing them, and it's still possible to cross-thread...
 
Joined
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'09, '14 Jetta
More suggestions to stay out of trouble

YMZ has it right: be gentle. My mistake was not logging on and looking around first! Had I known that 1) they are fine threads, 2) that the block is aluminum, and 3) that folks had troubles in the past, I wouldn't be where I am now. Here's what I did wrong:

I assumed that the GPs were robust little buggers similar to spark plugs. I just reached for the deep socket and started cranking. Two came out very easily, and two were difficult. They turned out fine, but there was a lot of friction the whole way out.

When replacing the plugs, I made no special attempt to put them in carefully and I didn't lube them up. The first two went in fine, despite my ignorance (they were the two easy ones on the way out). The third one didn't feel right going in, but it had been hard coming out. After going about 3/4 of the way in, the wrench torqued out. BUT... the torque went up very slowly and it didn't feel like it had seated correctly. It just kept getting tighter and tighter until the wrench clicked. Not a good sign. So I gently kept trying to tighten it. After about another 90 degrees I knew something was wrong so I backed it out. Sure enough! All the male threads were rounded over to about 3/4 of the way up. Then there was ~1.5 turns of thread that was filled with aluminum!

This GP wasn't "cross threaded". Rather, there was some corrosion or particle lodged in the threads that caused it to gradually tighten up as I kept deforming the threads. That's why I'm hoping a thread restoration tool (i.e. tap) will fix the problem without a HeliCoil.

Had I known what to look for, I would have stopped as soon as I encountered resistance. Heck! I woulda chased the old hole after it backed out with effort. I certainly NEVER would have tried to continue threading down a hole that "didn't feel right".

Clean it up before you back out the old one (throttle / carb cleaner soak followed by compressed air). Penetrating oil is a good idea too.

If you can't spin the new GP in using just your finger tips, something is wrong. Back out, take a break, collect your thoughts (and anti-sieze), and think it through. At this point running a chasing tap down the hole should work fine (use the earplug!).

There is no reason to strip the threads, and no reason to dread it if you know what could go wrong.

Oh yeah! That 4th plug? After messing up the third one, I took a day off and read this thread. Then I went back out to the car, cleaned up the hole (earplug, solvent, air, corkscrew to remove the plug), c-a-r-e-f-u-l-l-y hand threaded the replacement in, and all went well. The new one went in easier than the old one came out.

TCK
 
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jasonTDI

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20' RAM 3500 CCLB dually HO/Aisan. 2019 Cherokee 2.0T
LOL!

YMZ's copy and paste is spot on. I've replaced ans repaired a LOT and I mean a LOT of broken or stripped GP's.
 

LurkerMike

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Never remove threaded parts or fasteners from warm or hot aluminum! Work them out carefully only when the aluminum is room temprature.
 

sthussey

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And something I learned from DBW in a similar situation. Don't work on your engine if it is filthy. Take the time to wash it down so there isn't a bunch of crud sitting around the holes to fall into the cylinder or get stuck in the threads.
 

PDJetta

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'04 Jetta GLS TDI Pumpe Duce Platinum Grey w/ Leather
That's a very good point! Get the greasy dirt, and sand out. Especially when pulling the valve cover. I use "Gunk" brand cleaner, but sparingly, and just on real greasy areas. Simple Green works on less greasy areas. I did find out a couple weeks ago that if "Gunk" gets in between the engine and transaxle, the clutch will slip for a couple of weeks.

--Nate
 

jasonTDI

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Simple green is bad for aluminum. Mixed down not nearly as bad as strait.

Brake cleaner works REAL well for small areas like this and then follow with compressed air BEFORE disassembly.
 

tornadored7

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GMTLand
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GP crossthread near miss

This isn't completely related to the GP thread damage thread (sorry about the pun!), but I feel it's somewhat relevant.

As a relative newbie, I followed Wingnut's excellent GP diagnosis and replacement guide with trepidation.

I learnt alot and wanted to log my newbie experiences into Wingnut's GP 101. Will hopefully do that more fully when I get a better chance, but I felt a brief summary might be useful.

The Veteran's may find the write up below obvious and adding little extra knowledge, but I hope that it may prevent someone else having a possible GP crossthreading mishap.

In my situation, I had to replace all 4 GPs. (I had been driving for several years with 4 completely dead GPs and didn't realise it! What is suprising is that the Dealer didn't even point this out).

0) Ideally remove engine cover and gently wash the engine parts around the GPs with engine degreaser a couple of days before removing GPs. As sthussey, DBW, HermTDI and others have pointed out, the grease/grit and other contaminants not only make GP replacement alot more difficult, they can also harm the engine and GP threads/hole.

1) Allow engine to warm up to mid temperature guage. Remove GP wiring harness then spray WD40 around seat of GP and allow to penetrate. I then let the engine cool down for around 20 mins.

2) GENTLY loosen all GPs. (I used a 10mm deep socket attached to a 6 inch extension on a 3/8 rachet: for my 1Z engine).

Only remove and replace ONE GP at a time. That way if you have a problem reinserting/crossthreading a glowplug you won't panic at the thought of this happening to the remaining GPs, since you can simply retighten the GPs you haven't yet removed.

3) If you are replacing all GPs, work in a systematic way so that it is clear which GPs have been replaced. i.e. left to right. On a 1Z engine I found left to right to be a particularly good order, since the leftmost GP is easily accessible and less fiddly.

Further, starting with this easier GP will give you a good feel for how easily a plug should come out and the tightening torque, which becomes important when dealing with the more awkward middle GPs.

4) When a GP is removed, carefully but thoroughly clean the GP hole with a clean lint free cloth. This is important, otherwise the new GP's threads may be contaminated with dirt/grit preventing the new GP from screwing in. Capping the hole with a cloth, I also cleaned around the hole to allow proper GP seating and prevent possible dirt ingress.

5) As Wingnut describes, apply a small amount of Copper based antisieze/copper paste to the thread of the new GP. Inspect the thread to ensure that there is no dirt/grit on the thread.

6) Patiently try and carefully screw the GP back into it's hole by hand, for 3 turns (this is more difficult for the inner two GPs).

If the plug doesn't turn in, remove it and try again. It may be necessary to remove any grit/dirt that has just been collected in the GP thread, and to clean and reapply copper antisieze.

7) Again using a 10mm Deep Socket on a 6 inch extension, try and tighten the GP back into the hole.

In my case, this seemed to work without any issues for the easily accessible GP (leftmost). However, the inner GPs (2nd from left, 3rd from left) always seemed to crossthread when tightened.

This is where I panicked, since I had read about cross threading resulting in serious cylinder head removal issues. :eek:

After some thought I realised that the less accessible GPs, made an awkward angle with the socket, and that this was probably causing the crossthreading. Wingnut suggested using a wobble socket, so I used a Universal Joint to couple the 10mm Deep Socket to the extension bar. i.e.
10mm deep socket=>Universal Joint=>6 inch extension bar=>rachet.

The lack of accesibility made the rachet sit at the wrong angle to the glowplug, but when employing a Universal Joint, the UJ allowed the Deep socket to sit squarely on the GP reducing the possibility of crossthreading.

The first few turns were quite loose, but then the GP became more difficult to tighten and so I thought the glow plug had been installed, but checking the height of the GP above the engine it was clear the GP had many more turns before it was seated.

I continued tightening the GP despite the resistance, all the time thinking about the possibility that I may have been cross threading it. Fortunately, the GP wasn't cross threading, it was just that after the first few turns more torque was required to tighten the plug.

8) I tightened the GP, until it was sitting at the surface of the engine. For the all important final tightening I tried using a Torque Wrench to achieve the 15Nm Tightening Torque, but this felt as if it was overtightening and hence leading to possible damage.

Instead I opted for hand tight, plus 20 to 30 degrees of additional tightness.

Personally I feel that

a) being gentle and patient
b) only removing one GP at a time
c) using the Universal Joint on the 10mm Deep Socket
d) ensuring that the hole threads and GPs are dirt/grit free

helped to reduce the possibility of crossthreading the GPs.

10mm DS | UJ | 6in extension | rachet

Apologies to UNIX users for the pipe analogy. :)
 
Joined
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Location
Green Bay, WI
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'09, '14 Jetta
I promised an update on how my boogered threads went.

I'm pleased to report that all is now well, but it did cost me some wear and tear on the stomach lining!

Indeed the first 2-3 threads had been completely mangled. I'm still not sure how, but it was probably some grit that led to siezing it up.

Using the suggestion of drilling out the damaged threads worked, but only just barely. I used a home-made drill stop, and the drill grabbed so severely that I thought I had surely destroyed the head. Fortunately, I was using a 12 Volt battery powered drill and not my 115 V arm-buster drill! If I had to do it again, I'm not sure I would try drilling first. The resulting scarred up hole gave me nightmares all night long.

Today the new tap arrived (indeed, it is a M10x1.0 thread, NOT M11x1.0 as somebody previously suggested). It was a standard taper tap.

Next problem: A standard length tap is too short to reach down to the hole and still get a tap wrench on it! I tried repeatedly to thread the tap by hand, gently rocking it and twisting back and forth to try to catch the existing threads, but to no avail. It kept digging in and bogging down.

After a lot of creative vocabulary, I went down to a local hardware store and finally found a 12 point deep socket that would fit over the end of the tap and could be used to drive it.

This proved to be the cat's meow! With a long extension on the deep 12 point socket, I was able to ensure that I had pure torsion and no side-load on the tap, and that the tap was aligned with the axis of the hole. The tap threaded right in, and I drove it all the way down without even using a ratchet (finger pressure on the extension only!).

A short time later the new GP torqued, the rest of the engine back together (I had removed various interfering fuel lines, an injector hold-down, etc. to get an unobstructed view & access to the GP hole). It ran just fine, and after clearing the engine trouble light (reset with an OBD II code reader), it has not come back on.

Oh yeah! FOD control: the earplug trick was a lifesaver! Worked like a charm, and I was able to clean the entire area with solvent & air with the plug in place. To remove it, I bent a left-handed corkscrew out of some fine weld rod and sharpened the end. It turned the foam plug right out.

I also spoke to my local VW dealer's service manager. He acknowledged that THEY frequently have problems with the GPs sticking or even breaking off in the head. Maybe VW will do something to improve the situation in their next TDI model.

KD
 

ymz

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knuckle-dragger said:
Maybe VW will do something to improve the situation in their next TDI model.
Well, at least they changed the plugs - for the worse, in my opinion...
The new ceramic glow plugs used in the PD engines can also break off inside the cylinder head (or worse, inside the combustion chamber) shatter in addition to all the problems of cross-threading that can arise wth the older GP's...

Nice going with your project, and thanks for sharing !!!!

All the best,

Yuri.
 

mijbo11

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Saskatoon SK Canada
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1999 A3 Jetta
GRY_03TDI said:
I was going to coat the tap in grease to catch the metal flakes. That is how most of the aftermarket supercharger kits have you tap the oil pan. Things may be different when working right above the cylinder though. Then change the oil after the initial startup. I was not planning on drilling and inserting a helicoil. Are you sure about the 11mm? I found the 12mm online and ordered that tap. Knowing my luck with all this it will be 11mm and I will have to order more stuff. Thanks for the reply!
you wont catch all the flakes
 

cbass94

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Jun 14, 2006
Location
Salt Lake City, UT
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2003 Jetta GLS, 2011 JSW
Well, chalk up one more person that this happened to. The first three old plugs came out just fine and the corresponding new ones went in just fine. Then I got to the fourth plug. It seemed to have a really hard time coming out also (as others have mentioned above). I unthreaded it and the threads looked slightly different the the rest of the GP's, but I didn't think much of it. With a flash light, I looked in the hole and all looked OK. I put the new one in and started tightening. I soon met resistance and backed it back out all the way. I did the counter-clockwise turning until I thought I felt the groove of the threads and started tightening again. It just wasn't going. I was stumped. I figured either I cross-threaded it or something marred the threads when the old GP came out.

Anyway, after doing some searching, I found this tool.... http://www.sjdiscounttools.com/kdt3688.html

It says 10MM, do you guys think this would fit the GP's on our car?

This would definitely be a preferred method to fixing this problem because you insert the tool all the way into the compressio chamber and then flare the threaded part out so you can start the threading on the good threads at the bottom of the hole. Then you simply turn from inside out and it will clean and re-align the threads without the fear of dropping as much gunk into the cylinder. So, my question, do you guys think the threads are the same?

Thanks
 
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LurkerMike

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ymz

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cbass94 said:
It says 10MM, do you guys think this would fit the GP's on our car?
The glow plug threads on the TDI's are M10x1 (same as the sparkplugs on MOST late model motorcycle engines).

There should be a way to find out if there are any exceptions...

Yuri.

PS: when we recently bought a Harbor Freight compression tester, it came with the wrong size adapter although the box indicated the correct size...
 

cbass94

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2003 Jetta GLS, 2011 JSW
The response from KD was that they don't know the thread pitch. I went ahead and bought it. Should be here later this week and I'll let you all know.

Thanks for the info Yuri.
 

PDJetta

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'04 Jetta GLS TDI Pumpe Duce Platinum Grey w/ Leather
When the tap arrives you may want to test thread a piece of metal and see if an old GP will thread into it properly before you thread the head.

--Nate
 

cbass94

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2003 Jetta GLS, 2011 JSW
PDJetta said:
When the tap arrives you may want to test thread a piece of metal and see if an old GP will thread into it properly before you thread the head.

--Nate
Yeah, I'll definitely check to make sure the threads are correct first, but it's not actually a tap and likely would not cut new threads. It's only made to "chase and face" the threads that are already there.
 

rotarykid

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Sorry for your trouble . To avoid this ;

Don't ever remove anything from the head before cleaning it throughly , removing all dirt & crud first . ANY crud or dirt that falls into an aluminum hole with threads must be removed before the threaded object ( glow plugs , bolts , studs , injector are reincerted .
 

EddyKilowatt

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2003 Golf GL 5M
slowly turn it backwards (counter-clockwise) a little bit 'till it finds the groove entrance
Good advice any time you are starting a fastener into threads in a softer material. Even more so if the 'soft material' is plastic.

Eddy
 

Franko6

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Here is something that I almost never hear anybody mention. It's that the fourth g.p. and why it it difficult. That is because the vacuum resevoir is IN THE WAY!

it is so simple to remove the resevoir and keep yourself from stripping the #4 g.p. it's two torx screws, but in a pinch you can make an allen work. It's not like they are either long or tight. But if you don't get the resevoir out of the way, the deep socket rubs against the side of the resevoir and will make removing the plug an opportunity to mess the threads up.

Also, I've a method that seems, strangely enough, to help in odd situations. Before you loosen a bolt or nut, TIGHTEN IT. Also, the use of a penetrating oil on the threads as you extract it, especially if there is corrosion will help immensely. If the threads tighten in the hole while removing it, soak with a penetrating oil and put the glow plug back in. Work it in and out until it comes out smoothly.

When reinstallinga troublesome glow plug, a bottoming tap is a good idea for threads that were tight. There isn't much of anything that really helps to remove the material from the hole. Even if using a paste type grease, the particles are driven in front of the tap. If you are worried about the foreign matter in the cylinder, remove the injector, rotate the engine so the exhaust is open and blow pressurized air into the chamber. The good thing is that any particles will fall into the combustion chamber and will most likely be vented straight out the exhaust. There is not a great fear that any real damage would be done. I sure wouldn't remove a head for something like that.

Now about the heli-coils.. This is not a good place for a heli-coil. It would be better to broach the hole and weld and retap the hole for your glow plug threads if it is totally ruined.

The best thing to prevent such an issue is to avoid road salts in the head and use an heat resistant anti-seize preparation like Permatex. The same is true for injectors. They have the same propesity for reactive corrosion and aluminum oxide formation.
 
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