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Broken coil pack bolt

14K views 11 replies 7 participants last post by  Mongo53 
#1 ·
Was changing plugs tonight, and I am tightening up all the coil pack bolts (2 bolts per coil pack). I had my torque wrench set to 10 ft/lbs (not entirely sure on the proper spec), but the bolts seemed to turn forever to hit the torque setting... once it got past finger tight, the amount of resistance I felt seemed consistent until the wrench finally clicked. I don't know if they were going too far deep or what.

Anyway, 3 bolts from being done. Driver side, 3rd bolt back from the front, it's almost all the way in and SNAP... seems to have sheared off right at the edge of the valve cover. I didn't remove the coil pack as it is on tight with the other bolt and doesn't seem like it will go anywhere. I may just leave it like this, at least until it's time for new plugs... but then the problem could be worse.

I'd imagine it'd twist out easily if I could get something to turn it. The bolts were very easy to finger twist in/out when loose. I've never removed a broken bolt though. I probably broke the best bolt I could as it is accessible with a drill, but I don't know what I'm doing if I were to try to remove it... thoughts?


 
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#2 ·
Damn! That really sucks. I know your pain!
My advice would be to pick up a set of left hand drill bits. They spin counter clockwise so you may actually spin the bolt out as you drill a pilot hole for an EZ out. More than once has this worked for me on various project vehicles. If you choose this route make sure you put painters tape over the plug hole and the other coil bolt hole so no shavings get in there.
Another trick that has gotten me out of a pickle is to JB weld or epoxy the two bolt halves back together then remove the bolt after it sets. On the plus side, if you try this first and it doesn't work then you can try the lefty drill bit.
I attached the page for the torque values. You can see it isn't much for the coil packs.
 

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#3 · (Edited)
Well **** me! I saw in a few places, and was told by someone (at least for their 2012) that the torque value was like 18-23 ft/lbs... they were clearly confused with N*m! I set my wrench to 22 ft/lbs, but with a wobble socket so it wasn't quite that high... but still. I have driven about 100 miles with the plugs at nearly 2x the torque value. And clearly the coil packs are nearly 2x the torque as well. I'm guessing I need to get in there and re-do it all? What are the odds anything was damaged? :mad:

I was also a bit rushed and did it when the engine was still warm. Plugs weren't scalding hot when I pulled them, but not cool enough I'd want them in my hand for a long time either. Maybe the heat-expanded threads will somehow result in a lower cold-torqued value?.. going to let it cool down tonight and re-torque them tomorrow.
 
#4 ·
Got everything retorqued tonight. Most of the plugs were surprisingly hard loosen up... hopefully no lasting damage was done and the plugs still seal properly. The 13~ ft lbs felt like a lot less when torquing. Also tried setting my torque wrench to 6 ft lbs for the coil packs, but even that felt like a lot... and my previous torquing put some hairline cracks in the plastic walls of the screw holes on the packs... so I just finger tightened then used a small ratchet until I felt some resistance.

Took her for a drive and all seems well.
 
#8 ·
Got everything retorqued tonight. Most of the plugs were surprisingly hard loosen up... hopefully no lasting damage was done and the plugs still seal properly. The 13~ ft lbs felt like a lot less when torquing. Also tried setting my torque wrench to 6 ft lbs for the coil packs, but even that felt like a lot... and my previous torquing put some hairline cracks in the plastic walls of the screw holes on the packs... so I just finger tightened then used a small ratchet until I felt some resistance.

Took her for a drive and all seems well.
You should be ok. Good thing you went in and redid them. On threaded fasteners a hot torque would be more due to expansion. I can't say what the effect would be on plugs since you aren't fastening two objects together. On the coil packs it is just snug really. I initially used my micro torque wrench but ended up just using a 1/4" ratchet instead. In lb-ft it is just less than 5. If you went 6 lb-ft its fine.

No, nothing on the plugs because NGK specifically recommends against it. It can cause you to over torque the plugs, and is unnecessary according to them. I do put a dab on dielectric grease in the boots and spread it with a q-tip.

Nothing on the coil pack bolts either. I'm not sure what material those bolts are... but the screw holes/receiving threads seemed to be gold plated?
Correct! 99% of modern plugs are plated and no longer require anti seize on the threads. That goes back to the days of heads made from ferrous metal and unplated plugs.
Maybe the threaded inserts are brass for corrosion resistance?
Tech bulliten from NGK North America:
http://jenniskens.livedsl.nl/Technical/Tips/Files/Sparkplug NGK TB-0630111antisieze.pdf
 
#6 ·
No, nothing on the plugs because NGK specifically recommends against it. It can cause you to over torque the plugs, and is unnecessary according to them. I do put a dab on dielectric grease in the boots and spread it with a q-tip.

Nothing on the coil pack bolts either. I'm not sure what material those bolts are... but the screw holes/receiving threads seemed to be gold plated?
 
#9 ·
Hi, I bought a used jeep not to long ago seems to run ok. However I had a issue as well with breaking a coil stud. Its a 2007 jeep Grand Cherokee 3.7 l v6. And it kinda has me stumped, because where it is fastened there is a nut and washer on top and one under it that it sits on. The break was right over the bottom nut. I was able to back it out till it was loose from threads. It seems to be stuck on something. It does screw back in fine. I read something about a guy that had a similar issue on a Dakota and he said he just yanked it out. I just made a mess out of my wife's car I can't afford to have two broke. Lol
 
#10 ·
Once you snap your first bolt from over torqueing it will likely never happen again.

Right or wrong barring serious engine, transmission, differential, etc. repairs/rebuilds i use torque wrenches mostly on wheel lug nuts and seldom anywhere else where precise torque is required.
After loosening and tightening a million bolts over the decades i have a feel for how much torque a specific size bolt or spark plug requires.
For smaller bolts i typically use a 1/4" ratchet or wrench, for medium size bolts a 3/8" ratchet or wrench and for the big stuff its the 1/2" persuader. For spark plugs its only my trusty 3/8" ratchet.

Far as anti-seize on spark plug threads yeah a lot of people including mechanics claim not to do that.
But those people never had to deal with a seized steel threaded plug in an aluminum body. Ask me how i know.
Been using anti-seize on spark plugs for decades including on NGK plugs and never had an issue.
The trick is to use only a tiny amount spread across the threads basically only a trace of it on the plug's threads.
 
#12 ·
Torques specs are dry torques unless otherwise noted.... ....Cylinder head bolts should be lubricated....

Lubrication, and anti-seize lubricates, will increase the clamping force for the same torque, clamping force is pulling on the threads.... ...its easy to strip out threads using anti-seize..... .....Like Moparado said, just a tiny dab is all that is needed...

For plugs on a Chrysler that uses crush washers, I don't use a torque wrench, just follow the instructions on the box, tighten finger tight and and then make a 3/4 of a turn with the wrench (or whatever the box says) and sure enough you feel the torque to amount of turn go up drastically just around hitting that amount of turn prescribed on the box, meaning the washer is crushed and threads are tight....

The threads and the wrench give incredible amount of mechanical advantage, what feels only slightly tight is actually very tight, there is no need to haul off on a wrench, especially for smaller bolts....
 
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