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      07-12-2013, 09:39 PM   #1
drexplode
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Broken spark plug

I'm embarrassed to admit that I failed at changing the spark plugs in my new E90-335i LCI. I've changed plugs before in two others cars, specifically of the rings variety with success.

Long story short, I was following these instructions: http://www.e90post.com/forums/showthread.php?t=826823

Hand tightened the plug in cylinder one, set the snap-on torque wrench to 23Nm. Begin to tighten and then all of a sudden no resistance. Pull out the schawaben socket and extension to find this (see below). Stopped all activity, placed all removed components in trunk and shook my head for awhile.

Currently waiting for a flat bed to pull her out of the garage (AT) to drop off at the stealership. I'm hoping they can back out the threads, and suck out any broken particles (if any). I'm praying the cost is less <$500 for my embarrassing error.

Any encouraging thoughts/opinions would be appreciated.

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      07-12-2013, 09:47 PM   #2
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Sounds like your snap on tool needs to go in the trash (well swapped out but you get my point).

23NM should not be enough force to do that sort of damage...
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      07-12-2013, 10:14 PM   #3
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Yeah, there's no chance in hell that should have happened, the plug itself must have had some catastrophic flaw, perhaps in concert with some corrosion.

For future reference, when the threads are the only thing that remain, there's no force holding them in. You should have been able to reach in with even something like a wad of gum on a stick and twist it out, though I'd have tried something more like a tapered dowel slightly thinner than the thread peak diameter (jam it in to the lost thread shell, then unscrew the whole thing). Then once you've got the orphaned thread shell out, compare it to the remains of the spark plug to make sure no chips got left and fell into the cylinder.
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      07-12-2013, 10:34 PM   #4
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My first reaction was to stop and curse loudly (Italian genes). Afterwards, I decided to shut it down and allow the expensive professionals to take charge. My day as a home mechanic was over. Successful oil change on the B8-S4 was all that was going to happen today.

Flat bed trailer took her away and will be dropped off tonight.

Ironic thing - I work at Bosch as an enginerd. Might have to reach out and ask for an 8D!

FYI-to put an AT into neutral without turning on the engine: key in ignition slot, press engine start button (NO brake!), slide AT lever, remove key, repeat until in N
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      07-12-2013, 10:43 PM   #5
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Quote:
Originally Posted by drexplode View Post
Ironic thing - I work at Bosch as an enginerd. Might have to reach out and ask for an 8D!
hehe, irony indeed! Electrical or what?
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      07-12-2013, 11:10 PM   #6
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Originally Posted by alexwhittemore View Post
hehe, irony indeed! Electrical or what?
Electrical indeed. Explain why I failed a mechanical test? Kidding. I work in PFI/DI fuel injection.
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      07-12-2013, 11:17 PM   #7
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This ... Actually happened to me as well when I was changing my e30's plugs. Bosch plugs, set the correct torque limit on my wrench and .. Snap. I was able to jam a torx bit into the threaded bit and unscrew it without any damage. Shop vacuum whatever may have fallen into the cylinder head. 3 hours, lots of cursing (Russian genes. I'm told our swearing is the worst) and another trip to the parts store for a set of plugs.
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      07-13-2013, 02:29 AM   #8
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Quote:
Originally Posted by drexplode
My first reaction was to stop and curse loudly (Italian genes). Afterwards, I decided to shut it down and allow the expensive professionals to take charge. My day as a home mechanic was over. Successful oil change on the B8-S4 was all that was going to happen today.

Flat bed trailer took her away and will be dropped off tonight.

Ironic thing - I work at Bosch as an enginerd. Might have to reach out and ask for an 8D!

FYI-to put an AT into neutral without turning on the engine: key in ignition slot, press engine start button (NO brake!), slide AT lever, remove key, repeat until in N
Also you can pull the shifter boot up and you'll see a little piece of metal painted red. Pull it up and you can put the car in neutral. Without the car having power at all. ( battery cable completely went out 2 days ago, no power what so ever)
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      07-13-2013, 02:41 AM   #9
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I brought $50 to my Indy with plugs in hand and had him do it. Best money I ever spent
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      07-13-2013, 04:10 AM   #10
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You guys are doing it wrong aparently. Always go hand tight plus a quarter turn!!
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      07-13-2013, 05:50 AM   #11
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I find this thread very interesting. The way that plug failed should have never happened unless it had a serious manufacturing defect.

So where did the new, broken, plug come from? From your picture, the plugs are totally different from manufacturing perspective. The used plug, which I presume is the OE plug that was installed at the engine factory, has different (ink) markings, and a different stamping process for the id numbers around the plug-body flat. Also, the compression washer is missing from the new plug, and is sitting on top of the thread body broken off in the head.

I'm curious to know if the plugs have a country of manufacture on them somewhere, or does the box that the broken plug came in have a country of manufacture on it? I'm wondering if the new plugs you bought were counterfeit. If it were me, I'd have all the plugs changed at the shop (since the car is now there) with new OE plugs sourced from BMW.

You seriously have a claim here against Bosch in my opinion. Have the dealership give you the parts (including the compression washer) as evidence. The amount the compression washer is crushed will be the telltale sign on how much torque was applied to the plug when you were setting it; it would be seriously deformed if the amount of torque needed to snap a plug like that was actually applied to it. Bosch will obviously say you over torqued the plug and caused it to snap in half.

Finally, when I set the torque on plugs, I use a beam-type 3/8-drive torque-wrench (Craftsman). Beam torque-wrenches are far more accurate at small torque values than a click-type torque-wrench. Not trying to flame you here, but if you used a big, 1/2-drive click-type torque-wrench (like one uses to torque wheel bolts), then I could possibly see where you applied way too much torque to the plug (even at the wrench's lowest setting), but on the other hand I'd expect that situation to strip the treads out of the spark plug hole first.

Good luck.
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      07-13-2013, 07:02 AM   #12
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Quote:
Originally Posted by Efthreeoh View Post
I find this thread very interesting. The way that plug failed should have never happened unless it had a serious manufacturing defect.

So where did the new, broken, plug come from? From your picture, the plugs are totally different from manufacturing perspective. The used plug, which I presume is the OE plug that was installed at the engine factory, has different (ink) markings, and a different stamping process for the id numbers around the plug-body flat. Also, the compression washer is missing from the new plug, and is sitting on top of the thread body broken off in the head.

I'm curious to know if the plugs have a country of manufacture on them somewhere, or does the box that the broken plug came in have a country of manufacture on it? I'm wondering if the new plugs you bought were counterfeit. If it were me, I'd have all the plugs changed at the shop (since the car is now there) with new OE plugs sourced from BMW.

You seriously have a claim here against Bosch in my opinion. Have the dealership give you the parts (including the compression washer) as evidence. The amount the compression washer is crushed will be the telltale sign on how much torque was applied to the plug when you were setting it; it would be seriously deformed if the amount of torque needed to snap a plug like that was actually applied to it. Bosch will obviously say you over torqued the plug and caused it to snap in half.

Finally, when I set the torque on plugs, I use a beam-type 3/8-drive torque-wrench (Craftsman). Beam torque-wrenches are far more accurate at small torque values than a click-type torque-wrench. Not trying to flame you here, but if you used a big, 1/2-drive click-type torque-wrench (like one uses to torque wheel bolts), then I could possibly see where you applied way too much torque to the plug (even at the wrench's lowest setting), but on the other hand I'd expect that situation to strip the treads out of the spark plug hole first.

Good luck.
Thanks for the feedback everyone.

The plugs were purchased from ECS Tuning, a trusted/reputable supplier in my opinion. I used them for just about all of my home mechanic needs to ensure the correct part number usage. Also, before beginning I verified the engraved manufacturer part number matched which is present above the crush washer; ZR5TPP33. OE shows an "s" afterwards which stands for OE. In my opinion, plugs are identical.

Also, the torque wrench was borrowed from work; meaning Bosch garage. My technicians use this tool on a regular basis which means every year it is calibrated internally; which includes a sticker.

Lastly, as I always do - applied a small amount of engine oil to the threads for smoother installation.

If I can get the threaded part back from the stealership then I will definite hand it to my spark plug engineer and ask him for his opinion. I still don't understand why this happened... head is still shaking.

Last edited by drexplode; 07-13-2013 at 07:09 AM.
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      07-13-2013, 07:37 AM   #13
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Never apply oil or anti-seize compound to a metal-plated plug such as those made by Bosch and NGK. The plugs that BMW uses have a very thin wall and must be torqued correctly. Adding oil or anti-seize makes it very easy to over-torque the plug and either damage the threads in the head or twist off the plug. NGK even has a tech bulletin out, complete with pictures, warning consumers not to use anti-seize on plated plugs:

http://www.ngksparkplugs.com/pdf/tb-...1antisieze.pdf
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      07-13-2013, 07:46 AM   #14
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Quote:
Originally Posted by drexplode View Post
Thanks for the feedback everyone.

The plugs were purchased from ECS Tuning, a trusted/reputable supplier in my opinion. I used them for just about all of my home mechanic needs to ensure the correct part number usage. Also, before beginning I verified the engraved manufacturer part number matched which is present above the crush washer; ZR5TPP33. OE shows an "s" afterwards which stands for OE. In my opinion, plugs are identical.

Also, the torque wrench was borrowed from work; meaning Bosch garage. My technicians use this tool on a regular basis which means every year it is calibrated internally; which includes a sticker.

Lastly, as I always do - applied a small amount of engine oil to the threads for smoother installation.

If I can get the threaded part back from the stealership then I will definite hand it to my spark plug engineer and ask him for his opinion. I still don't understand why this happened... head is still shaking.
I missed the point that you still work at Bosch. I'd work it internally then.
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      07-13-2013, 07:51 AM   #15
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Quote:
Originally Posted by DJtoad View Post
Never apply oil or anti-seize compound to a metal-plated plug such as those made by Bosch and NGK. The plugs that BMW uses have a very thin wall and must be torqued correctly. Adding oil or anti-seize makes it very easy to over-torque the plug and either damage the threads in the head or twist off the plug. NGK even has a tech bulletin out, complete with pictures, warning consumers not to use anti-seize on plated plugs:

http://www.ngksparkplugs.com/pdf/tb-...1antisieze.pdf
I missed that part, thinking 100% counterfeit or defective plug.

I don't think the torque is accurate once a lubricant is applied to the threads, they say the same about lugs on wheels.

OP, I feel your pain, I stripped the threads on my parent's Toyota when I was 18 and left for college....
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      07-13-2013, 08:28 AM   #16
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Quote:
Originally Posted by John 070
Quote:
Originally Posted by DJtoad View Post
Never apply oil or anti-seize compound to a metal-plated plug such as those made by Bosch and NGK. The plugs that BMW uses have a very thin wall and must be torqued correctly. Adding oil or anti-seize makes it very easy to over-torque the plug and either damage the threads in the head or twist off the plug. NGK even has a tech bulletin out, complete with pictures, warning consumers not to use anti-seize on plated plugs:

http://www.ngksparkplugs.com/pdf/tb-...1antisieze.pdf
I missed that part, thinking 100% counterfeit or defective plug.

I don't think the torque is accurate once a lubricant is applied to the threads, they say the same about lugs on wheels.

OP, I feel your pain, I stripped the threads on my parent's Toyota when I was 18 and left for college....
the torque on the part is the same no matter what lube is used, the only thing that changes is the axial load.

I too think this is either a defective part or a defective torque wrench...
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      07-13-2013, 08:50 AM   #17
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Quote:
Originally Posted by N8N View Post
the torque on the part is the same no matter what lube is used, the only thing that changes is the axial load.
That's correct. Axial load is a function of the amount of torque applied, diameter of the plug, and the friction coefficient. Reducing the friction results in an increase in axial load for a given amount of torque. If the axial load is too great, the bolt (or in this case, the plug) will snap off.
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      07-13-2013, 08:52 AM   #18
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Quote:
Originally Posted by N8N View Post
the torque on the part is the same no matter what lube is used, the only thing that changes is the axial load.

I too think this is either a defective part or a defective torque wrench...
Nah. That's why there are dry, and lubed torque values.

imho the NGK bulletin speaks volumes.

http://www.imperialsupplies.com/pdf/...rqueCharts.pdf
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      07-13-2013, 09:07 AM   #19
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Quote:
Originally Posted by N8N View Post
the torque on the part is the same no matter what lube is used, the only thing that changes is the axial load.

I too think this is either a defective part or a defective torque wrench...
My guess would be a defective torque wrench. Happened to me with my e46. I snapped a watepump bolt and I threw the wrench across the yard. Never used one again.
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      07-13-2013, 11:07 AM   #20
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Quote:
Originally Posted by Chriztofor View Post
My guess would be a defective torque wrench. Happened to me with my e46. I snapped a watepump bolt and I threw the wrench across the yard. Never used one again.
I may have found the root cause: defective torque wrench? I tested it on another bolt and set the torque really low to trigger the "click". The audible "click" and feel was ever so faint. To put things into perspective, I had to test it about 3-4x to notice something. The audible click i'm used to is from wheel bolts on my craftsman t-wrench.

That being said, I'm sure that I over-torque the spark plug because I was waiting for the "click". Common sense eventually kicked in; however, I went a few 1/4 turns thinking nothing of it because the hand tight was a little slippery from dis-assembly schmutz.

I spoke to the dealer this morning and they will start the work on Monday. I will follow-up with spark plug enginerd at work and ask for an opinion.
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      07-13-2013, 02:34 PM   #21
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Even Denso recommends"not" using lubricants on the spark plug thread. It messes up the torque values.

By the way the best way to tighten the spark plug is first by hand and then by wrench till you feel resistence and then quarter of a turn till. Then STOP! I always read what the manufacturer recommends (on their web site) both with torque wrench and without torque wrench before I proceed.
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      07-13-2013, 03:33 PM   #22
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Quote:
Originally Posted by drexplode View Post
I may have found the root cause: defective torque wrench? I tested it on another bolt and set the torque really low to trigger the "click". The audible "click" and feel was ever so faint. To put things into perspective, I had to test it about 3-4x to notice something. The audible click i'm used to is from wheel bolts on my craftsman t-wrench.

That being said, I'm sure that I over-torque the spark plug because I was waiting for the "click". Common sense eventually kicked in; however, I went a few 1/4 turns thinking nothing of it because the hand tight was a little slippery from dis-assembly schmutz.

I spoke to the dealer this morning and they will start the work on Monday. I will follow-up with spark plug enginerd at work and ask for an opinion.
That would explain it considering how thin-walled the plug design apparently is. Get a Craftsman 3/8-drive beam-style torque-wrench, they are about $20.

Lesson learned I guess. An easyout would have pulled the broken part right out for you.
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