New coil pack - how to avoid snapping off the bolt?

[Chickenhawk]

Sudden misfires and a flashing check engine light made me break out the Tech 2 and confirm cylinder #3 was constantly misfiring when warm. Thankfully I have a new Delphi coil pack in a box and will pull it out tomorrow. I am just worried about breaking off the bolt in the block while removing. Warm engine or cold? Small impact or ratchet? Any ideas on how to avoid snapping off the bolt?

Or am I just overthinking this. I have done two spark plug changes (230,000 km) and didn't have issues with the bolts before, but it's been many years since the last plug change.

If I remember correctly, torque value on the bolt is 89 inch-pounds.

 

[flyboy2610]

I would use a small ratchet and first tighten the bolt just a hair, then back it out a bit. Repeat the process until the bolt comes out.

 

[mrrsm]

Not Possible...and ill-advised. The M6 X 1.00 X 12mm bottom threaded portion on the COP Fastener unfortunately has an abrupt Shoulder that, if the fastening torque exceeds 89 Inch Pounds inwards, will invariably bottom out and snap off that 12mm long bolt section inside of the upper head.

You might try spraying down the top of the fastener with this stuff... to lower its temperature...along with ensuring that the Aluminum Engine head is also cold... and very gradually, patiently apply a counter-clockwise turning.

This Linked "Thread" thoroughly describes what to do if this bolt-snapping accident should occur:

How to Repair Stripped Out 'Coil On Plug' Fasteners:

How to Repair Stripped Out COP Fasteners: If you make the mistake of “Honking Down” Too Hard on the Coil On Plugs Hold-Down Fasteners with anything more than 89 INCH Pounds of Torque… One of Two Bad things will very likely happen: (A) The Hold Down Bolt will Snap Off close to the Top of the...

gmtnation.com

 

[Mooseman]

I just did them without issues on a warm engine, however I replaced the plugs like 4 years ago/80k km and no issues then on a cold engine. Just loosen it with a ratchet. Don't try to tighten them before loosening as they are bottomed out.

 

[Chickenhawk]

Trust me, it's Winnipeg. Anything I would spray to cool it down would just be warmer than the ambient air anyway.

So far my thoughts are to do it when cold (brrr) but I am speculating that a 1/4" impact might just suddenly 'break free' any corrosion on the threads, whereas the ratchet might twist until it snaps. Kinda like removing a band aid. If you go slow, it hurts more. If you say, "Get ready. I will count down 3, 2, 1 and pull it off. Ready? 3 ..." YANK.

Works every time.

 

[mrrsm]

The problem that begs here though is that if everything is truly Ice Cold...any sudden jerking motions imparted by an impact tool might have the opposite effect, since all metals become so much more *brittle* in deep cold temperatures.

"Softly, Softly... Catchee Monkey..." --== Mr. Moto ==--

 

[krunal88]

I ended up snapping a coil pack bolt with a ratchet by over tightening. They don’t take much torque to snap. When you tighten, just snug em up a bit. I don’t think you’ll have much issue loosening them.

 

[Chickenhawk]

Yes, I was overthinking it. I put on a low-power battery impact and after a couple of hits, it popped right out. It took longer to remove the wiring clip with cold fingers than it did to replace the coil pack. Based on everyone's advice, I was very careful tightening the bolt. I use a 1/4-inch torque wrench but didn't go all the way to 89 inch-pounds, as it felt tight enough at about 70. Thanks everyone, and my misfire is now gone completely. So much fun to see the misfire graphic at dead zero across the board.

 

[mrrsm]

FWIW... I'd be curious to see what the Misfire History was on the cylinder populated with the failed COP. Most of the time... the cause and origin is either a problematic EFI or an adjacent Air Leak on the Intake Manifold that causes regular enough Lean Conditions to force the Secondary Side of the COP to jack up the Higher K-V enough to oscillate back and forth -=Llike a Friggin' Ping-Pong Ball=- well into the Primary Side and either Short it to Ground and-or leave Carbon Tracks inside the Rubber Boot and along the Porcelain Ceramic of the Spark Plug as the Coil fires -=OUTSIDE=- of the involved Cylinder.

This is the condition that can seriously over-heat the Primary Side of the Coil; often enough to damned near melt the Epoxy under the Heat Radiator on top and over-stress the internal controls of the COP. Low Hydro-Carbon Fuel to Ambient Air F/A Mixtures IS the underlying cause of why COPs mysteriously fail because the Plasma Arc needed for the Spark Ignition to easily occur demands having a RICHER Atomized Fuel Mixture be present in order to keep the COPS Happy by allowing the Spark Plug to Fire.

Just my...

 

[Chickenhawk]

You make some good points. Information wise, there was zero misfire history until it very suddenly died at idle, and cleared itself for a few minutes and died again, this time for good. Thankfully, I only had a few miles to go but the Check Engine light started flashing the last mile.

History wise, mixture conditions have been good and I have never had a single misfire code for the past twelve years. Even before that, I would have maybe five or ten misfires in an hour on three cylinders. (I changed the coils on those cylinders anyway, and the misfire graph has been zero every time I broke out the Tech 2 since then.)

I have been watching my O2 performance because I was getting a failure code in the rear every few months, and then about two weeks ago, I saw the front was getting a bit lazy (no code yet) but I changed both anyway.